qt,cpp: Consistently use nullptr and override

* lang/cpp/src/Makefile.am, lang/qt/src/Makefile.am (AM_CPPFLAGS):
Add suggest-override and zero-as-null-pointer-constant warnings.

* lang/cpp/src/*, lang/qt/src/*: Consistenly use nullptr and override.

--
This was especially important for the headers so that downstream
users of GpgME++ or QGpgME do not get flooded by warnings if
they have these warnings enabled.

It also improves compiler errors/warnings in case of accidental
mistakes.

37 files changed, 252 insertions, 250 deletions

diff --git a/lang/cpp/src/Makefile.am b/lang/cpp/src/Makefile.am
index 1e6bdc28..1b1de327 100644
--- a/lang/cpp/src/Makefile.am
+++ b/lang/cpp/src/Makefile.am
@@ -66,7 +66,8 @@ libgpgmepp_la_SOURCES = $(main_sources) $(gpgmepp_headers) context_vanilla.cpp \
                         $(interface_headers) $(private_gpgmepp_headers)
 
 AM_CPPFLAGS = -I$(top_builddir)/src @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
-              -DBUILDING_GPGMEPP
+              -DBUILDING_GPGMEPP -Wsuggest-override \
+              -Wzero-as-null-pointer-constant
 
 libgpgmepp_la_LIBADD = ../../../src/libgpgme.la @LIBASSUAN_LIBS@
 libgpgmepp_la_LDFLAGS = -no-undefined -version-info \
diff --git a/lang/cpp/src/callbacks.cpp b/lang/cpp/src/callbacks.cpp
index f7692a03..21c2a813 100644
--- a/lang/cpp/src/callbacks.cpp
+++ b/lang/cpp/src/callbacks.cpp
@@ -76,7 +76,7 @@ gpgme_error_t passphrase_callback(void *opaque, const char *uid_hint, const char
     PassphraseProvider *provider = static_cast<PassphraseProvider *>(opaque);
     bool canceled = false;
     gpgme_error_t err = GPG_ERR_NO_ERROR;
-    char *passphrase = provider ? provider->getPassphrase(uid_hint, desc, prev_was_bad, canceled) : 0 ;
+    char *passphrase = provider ? provider->getPassphrase(uid_hint, desc, prev_was_bad, canceled) : nullptr ;
     if (canceled) {
         err = make_error(GPG_ERR_CANCELED);
     } else {
diff --git a/lang/cpp/src/configuration.cpp b/lang/cpp/src/configuration.cpp
index 8ccc05e9..33c812f7 100644
--- a/lang/cpp/src/configuration.cpp
+++ b/lang/cpp/src/configuration.cpp
@@ -64,7 +64,7 @@ std::vector<Component> Component::load(Error &returnedError)
     //
     // 1. get a context:
     //
-    gpgme_ctx_t ctx_native = 0;
+    gpgme_ctx_t ctx_native = nullptr;
     if (const gpgme_error_t err = gpgme_new(&ctx_native)) {
         returnedError = Error(err);
         return std::vector<Component>();
@@ -74,7 +74,7 @@ std::vector<Component> Component::load(Error &returnedError)
     //
     // 2. load the config:
     //
-    gpgme_conf_comp_t conf_list_native = 0;
+    gpgme_conf_comp_t conf_list_native = nullptr;
     if (const gpgme_error_t err = gpgme_op_conf_load(ctx_native, &conf_list_native)) {
         returnedError = Error(err);
         return std::vector<Component>();
@@ -94,7 +94,7 @@ std::vector<Component> Component::load(Error &returnedError)
         }
 
         // now prevent double-free of next.get() and following:
-        head->next = 0;
+        head->next = nullptr;
 
         // now add a new Component to 'result' (may throw):
         result.resize(result.size() + 1);
@@ -115,7 +115,7 @@ Error Component::save() const
     //
     // 1. get a context:
     //
-    gpgme_ctx_t ctx_native = 0;
+    gpgme_ctx_t ctx_native = nullptr;
     if (const gpgme_error_t err = gpgme_new(&ctx_native)) {
         return Error(err);
     }
@@ -129,22 +129,22 @@ Error Component::save() const
 
 const char *Component::name() const
 {
-    return comp ? comp->name : 0 ;
+    return comp ? comp->name : nullptr;
 }
 
 const char *Component::description() const
 {
-    return comp ? comp->description : 0 ;
+    return comp ? comp->description : nullptr ;
 }
 
 const char *Component::programName() const
 {
-    return comp ? comp->program_name : 0 ;
+    return comp ? comp->program_name : nullptr ;
 }
 
 Option Component::option(unsigned int idx) const
 {
-    gpgme_conf_opt_t opt = 0;
+    gpgme_conf_opt_t opt = nullptr;
     if (comp) {
         opt = comp->options;
     }
@@ -160,7 +160,7 @@ Option Component::option(unsigned int idx) const
 
 Option Component::option(const char *name) const
 {
-    gpgme_conf_opt_t opt = 0;
+    gpgme_conf_opt_t opt = nullptr;
     if (comp) {
         opt = comp->options;
     }
@@ -177,7 +177,7 @@ Option Component::option(const char *name) const
 unsigned int Component::numOptions() const
 {
     unsigned int result = 0;
-    for (gpgme_conf_opt_t opt = comp ? comp->options : 0 ; opt ; opt = opt->next) {
+    for (gpgme_conf_opt_t opt = comp ? comp->options : nullptr ; opt ; opt = opt->next) {
         ++result;
     }
     return result;
@@ -186,7 +186,7 @@ unsigned int Component::numOptions() const
 std::vector<Option> Component::options() const
 {
     std::vector<Option> result;
-    for (gpgme_conf_opt_t opt = comp ? comp->options : 0 ; opt ; opt = opt->next) {
+    for (gpgme_conf_opt_t opt = comp ? comp->options : nullptr ; opt ; opt = opt->next) {
         result.push_back(Option(comp, opt));
     }
     return result;
@@ -194,17 +194,17 @@ std::vector<Option> Component::options() const
 
 static gpgme_conf_arg_t mygpgme_conf_arg_copy(gpgme_conf_arg_t other, gpgme_conf_type_t type)
 {
-    gpgme_conf_arg_t result = 0, last = 0;
+    gpgme_conf_arg_t result = nullptr, last = nullptr;
     for (gpgme_conf_arg_t a = other ; a ; a = a->next) {
-        gpgme_conf_arg_t arg = 0;
+        gpgme_conf_arg_t arg = nullptr;
         const gpgme_error_t err
             = gpgme_conf_arg_new(&arg, type,
-                                 a->no_arg                 ? 0 :
+                                 a->no_arg                 ? nullptr :
                                  type == GPGME_CONF_STRING ? a->value.string :
                                  /* else */                  static_cast<void *>(&a->value));
         if (err) {
             gpgme_conf_arg_release(result, type);
-            return 0;
+            return nullptr;
         }
         assert(arg);
         if (result) {
@@ -234,17 +234,17 @@ Level Option::level() const
 
 const char *Option::name() const
 {
-    return isNull() ? 0 : opt->name ;
+    return isNull() ? nullptr : opt->name ;
 }
 
 const char *Option::description() const
 {
-    return isNull() ? 0 : opt->description ;
+    return isNull() ? nullptr : opt->description ;
 }
 
 const char *Option::argumentName() const
 {
-    return isNull() ? 0 : opt->argname ;
+    return isNull() ? nullptr : opt->argname ;
 }
 
 Type Option::type() const
@@ -420,7 +420,7 @@ Argument Option::defaultValue() const
 
 const char *Option::defaultDescription() const
 {
-    return isNull() ? 0 : opt->default_description ;
+    return isNull() ? nullptr : opt->default_description ;
 }
 
 Argument Option::noArgumentValue() const
@@ -434,7 +434,7 @@ Argument Option::noArgumentValue() const
 
 const char *Option::noArgumentDescription() const
 {
-    return isNull() ? 0 : opt->no_arg_description ;
+    return isNull() ? nullptr : opt->no_arg_description ;
 }
 
 Argument Option::activeValue() const
@@ -501,7 +501,7 @@ Error Option::resetToActiveValue()
     if (isNull()) {
         return Error(make_error(GPG_ERR_INV_ARG));
     } else {
-        return Error(gpgme_conf_opt_change(opt, 1, 0));
+        return Error(gpgme_conf_opt_change(opt, 1, nullptr));
     }
 }
 
@@ -510,15 +510,15 @@ Error Option::resetToDefaultValue()
     if (isNull()) {
         return Error(make_error(GPG_ERR_INV_ARG));
     } else {
-        return Error(gpgme_conf_opt_change(opt, 0, 0));
+        return Error(gpgme_conf_opt_change(opt, 0, nullptr));
     }
 }
 
 static gpgme_conf_arg_t make_argument(gpgme_conf_type_t type, const void *value)
 {
-    gpgme_conf_arg_t arg = 0;
+    gpgme_conf_arg_t arg = nullptr;
     if (const gpgme_error_t err = gpgme_conf_arg_new(&arg, type, value)) {
-        return 0;
+        return nullptr;
     } else {
         return arg;
     }
@@ -594,8 +594,8 @@ const void *to_void_star(const unsigned int &i)
 template <typename T>
 gpgme_conf_arg_t make_argument(gpgme_conf_type_t type, const std::vector<T> &value)
 {
-    gpgme_conf_arg_t result = 0;
-    gpgme_conf_arg_t last = 0;
+    gpgme_conf_arg_t result = nullptr;
+    gpgme_conf_arg_t last = nullptr;
     for (typename std::vector<T>::const_iterator it = value.begin(), end = value.end() ; it != end ; ++it) {
         if (gpgme_conf_arg_t arg = make_argument(type, to_void_star(*it))) {
             if (last) {
@@ -693,14 +693,14 @@ unsigned int Argument::numElements() const
 const char *Argument::stringValue(unsigned int idx) const
 {
     if (isNull() || opt->alt_type != GPGME_CONF_STRING) {
-        return 0;
+        return nullptr;
     }
     gpgme_conf_arg_t a = arg;
     while (a && idx) {
         a = a->next;
         --idx;
     }
-    return a ? a->value.string : 0 ;
+    return a ? a->value.string : nullptr ;
 }
 
 int Argument::intValue(unsigned int idx) const
diff --git a/lang/cpp/src/configuration.h b/lang/cpp/src/configuration.h
index 6993b6dd..2e577156 100644
--- a/lang/cpp/src/configuration.h
+++ b/lang/cpp/src/configuration.h
@@ -145,7 +145,7 @@ private:
 class GPGMEPP_EXPORT Option
 {
 public:
-    Option() : comp(), opt(0) {}
+    Option() : comp(), opt(nullptr) {}
     Option(const shared_gpgme_conf_comp_t &gpgme_comp, gpgme_conf_opt_t gpgme_opt)
         : comp(gpgme_comp), opt(gpgme_opt) {}
 
@@ -228,7 +228,7 @@ class GPGMEPP_EXPORT Argument
     friend class ::GpgME::Configuration::Option;
     Argument(const shared_gpgme_conf_comp_t &comp, gpgme_conf_opt_t opt, gpgme_conf_arg_t arg, bool owns);
 public:
-    Argument() : comp(), opt(0), arg(0) {}
+    Argument() : comp(), opt(nullptr), arg(nullptr) {}
     //Argument( const shared_gpgme_conf_comp_t & comp, gpgme_conf_opt_t opt, gpgme_conf_arg_t arg );
     Argument(const Argument &other);
     ~Argument();
diff --git a/lang/cpp/src/context.cpp b/lang/cpp/src/context.cpp
index ce38db0b..1e8d8f09 100644
--- a/lang/cpp/src/context.cpp
+++ b/lang/cpp/src/context.cpp
@@ -1,6 +1,7 @@
 /*
   context.cpp - wraps a gpgme key context
   Copyright (C) 2003, 2007 Klarälvdalens Datakonsult AB
+                2017, 2018 Intevation GmbH
 
   This file is part of GPGME++.
 
@@ -94,7 +95,7 @@ static void percent_unescape(std::string &s, bool plus2space)
 
 void initializeLibrary()
 {
-    gpgme_check_version(0);
+    gpgme_check_version(nullptr);
 }
 
 Error initializeLibrary(int)
@@ -203,26 +204,26 @@ Context::~Context()
 
 Context *Context::createForProtocol(Protocol proto)
 {
-    gpgme_ctx_t ctx = 0;
+    gpgme_ctx_t ctx = nullptr;
     if (gpgme_new(&ctx) != 0) {
-        return 0;
+        return nullptr;
     }
 
     switch (proto) {
     case OpenPGP:
         if (gpgme_set_protocol(ctx, GPGME_PROTOCOL_OpenPGP) != 0) {
             gpgme_release(ctx);
-            return 0;
+            return nullptr;
         }
         break;
     case CMS:
         if (gpgme_set_protocol(ctx, GPGME_PROTOCOL_CMS) != 0) {
             gpgme_release(ctx);
-            return 0;
+            return nullptr;
         }
         break;
     default:
-        return 0;
+        return nullptr;
     }
 
     return new Context(ctx);
@@ -235,7 +236,7 @@ std::unique_ptr<Context> Context::create(Protocol proto)
 
 std::unique_ptr<Context> Context::createForEngine(Engine eng, Error *error)
 {
-    gpgme_ctx_t ctx = 0;
+    gpgme_ctx_t ctx = nullptr;
     if (const gpgme_error_t err = gpgme_new(&ctx)) {
         if (error) {
             *error = Error(err);
@@ -298,7 +299,7 @@ void Context::setDecryptionFlags(DecryptionFlags flags)
 
 Context::Private::Private(gpgme_ctx_t c)
     : ctx(c),
-      iocbs(0),
+      iocbs(nullptr),
       lastop(None),
       lasterr(GPG_ERR_NO_ERROR),
       lastAssuanInquireData(Data::null),
@@ -315,7 +316,7 @@ Context::Private::~Private()
     if (ctx) {
         gpgme_release(ctx);
     }
-    ctx = 0;
+    ctx = nullptr;
     delete iocbs;
 }
 
@@ -393,11 +394,11 @@ unsigned int Context::keyListMode() const
 
 void Context::setProgressProvider(ProgressProvider *provider)
 {
-    gpgme_set_progress_cb(d->ctx, provider ? &progress_callback : 0, provider);
+    gpgme_set_progress_cb(d->ctx, provider ? &progress_callback : nullptr, provider);
 }
 ProgressProvider *Context::progressProvider() const
 {
-    void *pp = 0;
+    void *pp = nullptr;
     gpgme_progress_cb_t pcb = &progress_callback;
     gpgme_get_progress_cb(d->ctx, &pcb, &pp);
     return static_cast<ProgressProvider *>(pp);
@@ -405,12 +406,12 @@ ProgressProvider *Context::progressProvider() const
 
 void Context::setPassphraseProvider(PassphraseProvider *provider)
 {
-    gpgme_set_passphrase_cb(d->ctx, provider ? &passphrase_callback : 0, provider);
+    gpgme_set_passphrase_cb(d->ctx, provider ? &passphrase_callback : nullptr, provider);
 }
 
 PassphraseProvider *Context::passphraseProvider() const
 {
-    void *pp = 0;
+    void *pp = nullptr;
     gpgme_passphrase_cb_t pcb = &passphrase_callback;
     gpgme_get_passphrase_cb(d->ctx, &pcb, &pp);
     return static_cast<PassphraseProvider *>(pp);
@@ -434,7 +435,7 @@ void Context::setManagedByEventLoopInteractor(bool manage)
 }
 bool Context::managedByEventLoopInteractor() const
 {
-    return d->iocbs != 0;
+    return d->iocbs != nullptr;
 }
 
 void Context::installIOCallbacks(gpgme_io_cbs *iocbs)
@@ -449,10 +450,10 @@ void Context::installIOCallbacks(gpgme_io_cbs *iocbs)
 
 void Context::uninstallIOCallbacks()
 {
-    static gpgme_io_cbs noiocbs = { 0, 0, 0, 0, 0 };
+    static gpgme_io_cbs noiocbs = { nullptr, nullptr, nullptr, nullptr, nullptr };
     // io.add == 0 means disable io callbacks:
     gpgme_set_io_cbs(d->ctx, &noiocbs);
-    delete d->iocbs; d->iocbs = 0;
+    delete d->iocbs; d->iocbs = nullptr;
 }
 
 Error Context::setLocale(int cat, const char *val)
@@ -505,7 +506,7 @@ Error Context::startKeyListing(const char *patterns[], bool secretOnly)
 #ifndef HAVE_GPGME_EXT_KEYLIST_MODE_EXTERNAL_NONBROKEN
     if (!patterns || !patterns[0] || !patterns[1]) {
         // max. one pattern -> use the non-ext version
-        return startKeyListing(patterns ? patterns[0] : 0, secretOnly);
+        return startKeyListing(patterns ? patterns[0] : nullptr, secretOnly);
     }
 #endif
     return Error(d->lasterr = gpgme_op_keylist_ext_start(d->ctx, patterns, int(secretOnly), 0));
@@ -542,7 +543,7 @@ KeyGenerationResult Context::generateKey(const char *parameters, Data &pubKey)
 {
     d->lastop = Private::KeyGen;
     Data::Private *const dp = pubKey.impl();
-    d->lasterr = gpgme_op_genkey(d->ctx, parameters, dp ? dp->data : 0, 0);
+    d->lasterr = gpgme_op_genkey(d->ctx, parameters, dp ? dp->data : nullptr, nullptr);
     return KeyGenerationResult(d->ctx, Error(d->lasterr));
 }
 
@@ -550,7 +551,7 @@ Error Context::startKeyGeneration(const char *parameters, Data &pubKey)
 {
     d->lastop = Private::KeyGen;
     Data::Private *const dp = pubKey.impl();
-    return Error(d->lasterr = gpgme_op_genkey_start(d->ctx, parameters, dp ? dp->data : 0, 0));
+    return Error(d->lasterr = gpgme_op_genkey_start(d->ctx, parameters, dp ? dp->data : nullptr, nullptr));
 }
 
 KeyGenerationResult Context::keyGenerationResult() const
@@ -566,7 +567,7 @@ Error Context::exportPublicKeys(const char *pattern, Data &keyData)
 {
     d->lastop = Private::Export;
     Data::Private *const dp = keyData.impl();
-    return Error(d->lasterr = gpgme_op_export(d->ctx, pattern, 0, dp ? dp->data : 0));
+    return Error(d->lasterr = gpgme_op_export(d->ctx, pattern, 0, dp ? dp->data : nullptr));
 }
 
 Error Context::exportPublicKeys(const char *patterns[], Data &keyData)
@@ -575,18 +576,18 @@ Error Context::exportPublicKeys(const char *patterns[], Data &keyData)
 #ifndef HAVE_GPGME_EXT_KEYLIST_MODE_EXTERNAL_NONBROKEN
     if (!patterns || !patterns[0] || !patterns[1]) {
         // max. one pattern -> use the non-ext version
-        return exportPublicKeys(patterns ? patterns[0] : 0, keyData);
+        return exportPublicKeys(patterns ? patterns[0] : nullptr, keyData);
     }
 #endif
     Data::Private *const dp = keyData.impl();
-    return Error(d->lasterr = gpgme_op_export_ext(d->ctx, patterns, 0, dp ? dp->data : 0));
+    return Error(d->lasterr = gpgme_op_export_ext(d->ctx, patterns, 0, dp ? dp->data : nullptr));
 }
 
 Error Context::startPublicKeyExport(const char *pattern, Data &keyData)
 {
     d->lastop = Private::Export;
     Data::Private *const dp = keyData.impl();
-    return Error(d->lasterr = gpgme_op_export_start(d->ctx, pattern, 0, dp ? dp->data : 0));
+    return Error(d->lasterr = gpgme_op_export_start(d->ctx, pattern, 0, dp ? dp->data : nullptr));
 }
 
 Error Context::startPublicKeyExport(const char *patterns[], Data &keyData)
@@ -595,18 +596,18 @@ Error Context::startPublicKeyExport(const char *patterns[], Data &keyData)
 #ifndef HAVE_GPGME_EXT_KEYLIST_MODE_EXTERNAL_NONBROKEN
     if (!patterns || !patterns[0] || !patterns[1]) {
         // max. one pattern -> use the non-ext version
-        return startPublicKeyExport(patterns ? patterns[0] : 0, keyData);
+        return startPublicKeyExport(patterns ? patterns[0] : nullptr, keyData);
     }
 #endif
     Data::Private *const dp = keyData.impl();
-    return Error(d->lasterr = gpgme_op_export_ext_start(d->ctx, patterns, 0, dp ? dp->data : 0));
+    return Error(d->lasterr = gpgme_op_export_ext_start(d->ctx, patterns, 0, dp ? dp->data : nullptr));
 }
 
 ImportResult Context::importKeys(const Data &data)
 {
     d->lastop = Private::Import;
     const Data::Private *const dp = data.impl();
-    d->lasterr = gpgme_op_import(d->ctx, dp ? dp->data : 0);
+    d->lasterr = gpgme_op_import(d->ctx, dp ? dp->data : nullptr);
     return ImportResult(d->ctx, Error(d->lasterr));
 }
 
@@ -623,7 +624,7 @@ ImportResult Context::importKeys(const std::vector<Key> &kk)
             *keys_it++ = it->impl();
         }
     }
-    *keys_it++ = 0;
+    *keys_it++ = nullptr;
     d->lasterr = gpgme_op_import_keys(d->ctx, keys);
     shouldHaveResult = true;
     if ((gpgme_err_code(d->lasterr) == GPG_ERR_NOT_IMPLEMENTED ||
@@ -642,16 +643,16 @@ ImportResult Context::importKeys(const std::vector<Key> &kk)
                 }
             }
         }
-        fprs.push_back(0);
+        fprs.push_back(nullptr);
         Data data;
         Data::Private *const dp = data.impl();
         const gpgme_keylist_mode_t oldMode = gpgme_get_keylist_mode(d->ctx);
         gpgme_set_keylist_mode(d->ctx, GPGME_KEYLIST_MODE_EXTERN);
-        d->lasterr = gpgme_op_export_ext(d->ctx, &fprs[0], 0, dp ? dp->data : 0);
+        d->lasterr = gpgme_op_export_ext(d->ctx, &fprs[0], 0, dp ? dp->data : nullptr);
         gpgme_set_keylist_mode(d->ctx, oldMode);
         if (!d->lasterr) {
             data.seek(0, SEEK_SET);
-            d->lasterr = gpgme_op_import(d->ctx, dp ? dp->data : 0);
+            d->lasterr = gpgme_op_import(d->ctx, dp ? dp->data : nullptr);
             shouldHaveResult = true;
         }
     }
@@ -667,7 +668,7 @@ Error Context::startKeyImport(const Data &data)
 {
     d->lastop = Private::Import;
     const Data::Private *const dp = data.impl();
-    return Error(d->lasterr = gpgme_op_import_start(d->ctx, dp ? dp->data : 0));
+    return Error(d->lasterr = gpgme_op_import_start(d->ctx, dp ? dp->data : nullptr));
 }
 
 Error Context::startKeyImport(const std::vector<Key> &kk)
@@ -680,7 +681,7 @@ Error Context::startKeyImport(const std::vector<Key> &kk)
             *keys_it++ = it->impl();
         }
     }
-    *keys_it++ = 0;
+    *keys_it++ = nullptr;
     Error err = Error(d->lasterr = gpgme_op_import_keys_start(d->ctx, keys));
     delete[] keys;
     return err;
@@ -729,9 +730,9 @@ Error Context::edit(const Key &key, std::unique_ptr<EditInteractor> func, Data &
     d->lastEditInteractor = std::move(func);
     Data::Private *const dp = data.impl();
     return Error(d->lasterr = gpgme_op_edit(d->ctx, key.impl(),
-                                            d->lastEditInteractor.get() ? edit_interactor_callback : 0,
-                                            d->lastEditInteractor.get() ? d->lastEditInteractor->d : 0,
-                                            dp ? dp->data : 0));
+                                            d->lastEditInteractor.get() ? edit_interactor_callback : nullptr,
+                                            d->lastEditInteractor.get() ? d->lastEditInteractor->d : nullptr,
+                                            dp ? dp->data : nullptr));
 }
 
 
@@ -741,9 +742,9 @@ Error Context::startEditing(const Key &key, std::unique_ptr<EditInteractor> func
     d->lastEditInteractor = std::move(func);
     Data::Private *const dp = data.impl();
     return Error(d->lasterr = gpgme_op_edit_start(d->ctx, key.impl(),
-                              d->lastEditInteractor.get() ? edit_interactor_callback : 0,
-                              d->lastEditInteractor.get() ? d->lastEditInteractor->d : 0,
-                              dp ? dp->data : 0));
+                              d->lastEditInteractor.get() ? edit_interactor_callback : nullptr,
+                              d->lastEditInteractor.get() ? d->lastEditInteractor->d : nullptr,
+                              dp ? dp->data : nullptr));
 }
 
 
@@ -764,9 +765,9 @@ Error Context::cardEdit(const Key &key, std::unique_ptr<EditInteractor> func, Da
     d->lastCardEditInteractor = std::move(func);
     Data::Private *const dp = data.impl();
     return Error(d->lasterr = gpgme_op_card_edit(d->ctx, key.impl(),
-                              d->lastCardEditInteractor.get() ? edit_interactor_callback : 0,
-                              d->lastCardEditInteractor.get() ? d->lastCardEditInteractor->d : 0,
-                              dp ? dp->data : 0));
+                              d->lastCardEditInteractor.get() ? edit_interactor_callback : nullptr,
+                              d->lastCardEditInteractor.get() ? d->lastCardEditInteractor->d : nullptr,
+                              dp ? dp->data : nullptr));
 }
 
 Error Context::startCardEditing(const Key &key, std::unique_ptr<EditInteractor> func, Data &data)
@@ -775,9 +776,9 @@ Error Context::startCardEditing(const Key &key, std::unique_ptr<EditInteractor>
     d->lastCardEditInteractor = std::move(func);
     Data::Private *const dp = data.impl();
     return Error(d->lasterr = gpgme_op_card_edit_start(d->ctx, key.impl(),
-                              d->lastCardEditInteractor.get() ? edit_interactor_callback : 0,
-                              d->lastCardEditInteractor.get() ? d->lastCardEditInteractor->d : 0,
-                              dp ? dp->data : 0));
+                              d->lastCardEditInteractor.get() ? edit_interactor_callback : nullptr,
+                              d->lastCardEditInteractor.get() ? d->lastCardEditInteractor->d : nullptr,
+                              dp ? dp->data : nullptr));
 }
 
 #pragma GCC diagnostic pop
@@ -800,7 +801,7 @@ Error Context::startTrustItemListing(const char *pattern, int maxLevel)
 
 TrustItem Context::nextTrustItem(Error &e)
 {
-    gpgme_trust_item_t ti = 0;
+    gpgme_trust_item_t ti = nullptr;
     e = Error(d->lasterr = gpgme_op_trustlist_next(d->ctx, &ti));
     return TrustItem(ti);
 }
@@ -920,7 +921,7 @@ DecryptionResult Context::decrypt(const Data &cipherText, Data &plainText, const
     d->lastop = Private::Decrypt;
     const Data::Private *const cdp = cipherText.impl();
     Data::Private *const pdp = plainText.impl();
-    d->lasterr = gpgme_op_decrypt_ext(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags), cdp ? cdp->data : 0, pdp ? pdp->data : 0);
+    d->lasterr = gpgme_op_decrypt_ext(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags), cdp ? cdp->data : nullptr, pdp ? pdp->data : nullptr);
     return DecryptionResult(d->ctx, Error(d->lasterr));
 }
 
@@ -935,7 +936,7 @@ Error Context::startDecryption(const Data &cipherText, Data &plainText, const De
     const Data::Private *const cdp = cipherText.impl();
     Data::Private *const pdp = plainText.impl();
     return Error(d->lasterr = gpgme_op_decrypt_ext_start(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags),
-                 cdp ? cdp->data : 0, pdp ? pdp->data : 0));
+                 cdp ? cdp->data : nullptr, pdp ? pdp->data : nullptr));
 }
 
 Error Context::startDecryption(const Data &cipherText, Data &plainText)
@@ -957,7 +958,7 @@ VerificationResult Context::verifyDetachedSignature(const Data &signature, const
     d->lastop = Private::Verify;
     const Data::Private *const sdp = signature.impl();
     const Data::Private *const tdp = signedText.impl();
-    d->lasterr = gpgme_op_verify(d->ctx, sdp ? sdp->data : 0, tdp ? tdp->data : 0, 0);
+    d->lasterr = gpgme_op_verify(d->ctx, sdp ? sdp->data : nullptr, tdp ? tdp->data : nullptr, nullptr);
     return VerificationResult(d->ctx, Error(d->lasterr));
 }
 
@@ -966,7 +967,7 @@ VerificationResult Context::verifyOpaqueSignature(const Data &signedData, Data &
     d->lastop = Private::Verify;
     const Data::Private *const sdp = signedData.impl();
     Data::Private *const pdp = plainText.impl();
-    d->lasterr = gpgme_op_verify(d->ctx, sdp ? sdp->data : 0, 0, pdp ? pdp->data : 0);
+    d->lasterr = gpgme_op_verify(d->ctx, sdp ? sdp->data : nullptr, nullptr, pdp ? pdp->data : nullptr);
     return VerificationResult(d->ctx, Error(d->lasterr));
 }
 
@@ -975,7 +976,7 @@ Error Context::startDetachedSignatureVerification(const Data &signature, const D
     d->lastop = Private::Verify;
     const Data::Private *const sdp = signature.impl();
     const Data::Private *const tdp = signedText.impl();
-    return Error(d->lasterr = gpgme_op_verify_start(d->ctx, sdp ? sdp->data : 0, tdp ? tdp->data : 0, 0));
+    return Error(d->lasterr = gpgme_op_verify_start(d->ctx, sdp ? sdp->data : nullptr, tdp ? tdp->data : nullptr, nullptr));
 }
 
 Error Context::startOpaqueSignatureVerification(const Data &signedData, Data &plainText)
@@ -983,7 +984,7 @@ Error Context::startOpaqueSignatureVerification(const Data &signedData, Data &pl
     d->lastop = Private::Verify;
     const Data::Private *const sdp = signedData.impl();
     Data::Private *const pdp = plainText.impl();
-    return Error(d->lasterr = gpgme_op_verify_start(d->ctx, sdp ? sdp->data : 0, 0, pdp ? pdp->data : 0));
+    return Error(d->lasterr = gpgme_op_verify_start(d->ctx, sdp ? sdp->data : nullptr, nullptr, pdp ? pdp->data : nullptr));
 }
 
 VerificationResult Context::verificationResult() const
@@ -1001,7 +1002,7 @@ std::pair<DecryptionResult, VerificationResult> Context::decryptAndVerify(const
     const Data::Private *const cdp = cipherText.impl();
     Data::Private *const pdp = plainText.impl();
     d->lasterr = gpgme_op_decrypt_ext(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags | DecryptVerify),
-                                      cdp ? cdp->data : 0, pdp ? pdp->data : 0);
+                                      cdp ? cdp->data : nullptr, pdp ? pdp->data : nullptr);
     return std::make_pair(DecryptionResult(d->ctx, Error(d->lasterr)),
                           VerificationResult(d->ctx, Error(d->lasterr)));
 }
@@ -1016,7 +1017,7 @@ Error Context::startCombinedDecryptionAndVerification(const Data &cipherText, Da
     d->lastop = Private::DecryptAndVerify;
     const Data::Private *const cdp = cipherText.impl();
     Data::Private *const pdp = plainText.impl();
-    return Error(d->lasterr = gpgme_op_decrypt_ext_start(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags | DecryptVerify), cdp ? cdp->data : 0, pdp ? pdp->data : 0));
+    return Error(d->lasterr = gpgme_op_decrypt_ext_start(d->ctx, static_cast<gpgme_decrypt_flags_t> (d->decryptFlags | flags | DecryptVerify), cdp ? cdp->data : nullptr, pdp ? pdp->data : nullptr));
 }
 
 Error Context::startCombinedDecryptionAndVerification(const Data &cipherText, Data &plainText)
@@ -1043,14 +1044,14 @@ Error Context::startGetAuditLog(Data &output, unsigned int flags)
 {
     d->lastop = Private::GetAuditLog;
     Data::Private *const odp = output.impl();
-    return Error(d->lasterr = gpgme_op_getauditlog_start(d->ctx, odp ? odp->data : 0, to_auditlog_flags(flags)));
+    return Error(d->lasterr = gpgme_op_getauditlog_start(d->ctx, odp ? odp->data : nullptr, to_auditlog_flags(flags)));
 }
 
 Error Context::getAuditLog(Data &output, unsigned int flags)
 {
     d->lastop = Private::GetAuditLog;
     Data::Private *const odp = output.impl();
-    return Error(d->lasterr = gpgme_op_getauditlog(d->ctx, odp ? odp->data : 0, to_auditlog_flags(flags)));
+    return Error(d->lasterr = gpgme_op_getauditlog(d->ctx, odp ? odp->data : nullptr, to_auditlog_flags(flags)));
 }
 
 void Context::clearSigningKeys()
@@ -1091,7 +1092,7 @@ GpgME::Error Context::addSignatureNotation(const char *name, const char *value,
 
 GpgME::Error Context::addSignaturePolicyURL(const char *url, bool critical)
 {
-    return Error(gpgme_sig_notation_add(d->ctx, 0, url, critical ? GPGME_SIG_NOTATION_CRITICAL : 0));
+    return Error(gpgme_sig_notation_add(d->ctx, nullptr, url, critical ? GPGME_SIG_NOTATION_CRITICAL : 0));
 }
 
 const char *Context::signaturePolicyURL() const
@@ -1142,7 +1143,7 @@ SigningResult Context::sign(const Data &plainText, Data &signature, SignatureMod
     d->lastop = Private::Sign;
     const Data::Private *const pdp = plainText.impl();
     Data::Private *const sdp = signature.impl();
-    d->lasterr = gpgme_op_sign(d->ctx, pdp ? pdp->data : 0, sdp ? sdp->data : 0, sigmode2sigmode(mode));
+    d->lasterr = gpgme_op_sign(d->ctx, pdp ? pdp->data : nullptr, sdp ? sdp->data : nullptr, sigmode2sigmode(mode));
     return SigningResult(d->ctx, Error(d->lasterr));
 }
 
@@ -1151,7 +1152,7 @@ Error Context::startSigning(const Data &plainText, Data &signature, SignatureMod
     d->lastop = Private::Sign;
     const Data::Private *const pdp = plainText.impl();
     Data::Private *const sdp = signature.impl();
-    return Error(d->lasterr = gpgme_op_sign_start(d->ctx, pdp ? pdp->data : 0, sdp ? sdp->data : 0, sigmode2sigmode(mode)));
+    return Error(d->lasterr = gpgme_op_sign_start(d->ctx, pdp ? pdp->data : nullptr, sdp ? sdp->data : nullptr, sigmode2sigmode(mode)));
 }
 
 SigningResult Context::signingResult() const
@@ -1199,7 +1200,7 @@ gpgme_key_t *Context::getKeysFromRecipients(const std::vector<Key> &recipients)
             *keys_it++ = it->impl();
         }
     }
-    *keys_it++ = 0;
+    *keys_it++ = nullptr;
     return ret;
 }
 
@@ -1213,7 +1214,7 @@ EncryptionResult Context::encrypt(const std::vector<Key> &recipients, const Data
     Data::Private *const cdp = cipherText.impl();
     gpgme_key_t *const keys = getKeysFromRecipients(recipients);
     d->lasterr = gpgme_op_encrypt(d->ctx, keys, encryptflags2encryptflags(flags),
-                                  pdp ? pdp->data : 0, cdp ? cdp->data : 0);
+                                  pdp ? pdp->data : nullptr, cdp ? cdp->data : nullptr);
     if (keys) {
         delete[] keys;
     }
@@ -1225,8 +1226,8 @@ Error Context::encryptSymmetrically(const Data &plainText, Data &cipherText)
     d->lastop = Private::Encrypt;
     const Data::Private *const pdp = plainText.impl();
     Data::Private *const cdp = cipherText.impl();
-    return Error(d->lasterr = gpgme_op_encrypt(d->ctx, 0, (gpgme_encrypt_flags_t)0,
-                              pdp ? pdp->data : 0, cdp ? cdp->data : 0));
+    return Error(d->lasterr = gpgme_op_encrypt(d->ctx, nullptr, (gpgme_encrypt_flags_t)0,
+                              pdp ? pdp->data : nullptr, cdp ? cdp->data : nullptr));
 }
 
 Error Context::startEncryption(const std::vector<Key> &recipients, const Data &plainText, Data &cipherText, EncryptionFlags flags)
@@ -1239,7 +1240,7 @@ Error Context::startEncryption(const std::vector<Key> &recipients, const Data &p
     Data::Private *const cdp = cipherText.impl();
     gpgme_key_t *const keys = getKeysFromRecipients(recipients);
     d->lasterr = gpgme_op_encrypt_start(d->ctx, keys, encryptflags2encryptflags(flags),
-                                        pdp ? pdp->data : 0, cdp ? cdp->data : 0);
+                                        pdp ? pdp->data : nullptr, cdp ? cdp->data : nullptr);
     if (keys) {
         delete[] keys;
     }
@@ -1262,7 +1263,7 @@ std::pair<SigningResult, EncryptionResult> Context::signAndEncrypt(const std::ve
     Data::Private *const cdp = cipherText.impl();
     gpgme_key_t *const keys = getKeysFromRecipients(recipients);
     d->lasterr = gpgme_op_encrypt_sign(d->ctx, keys, encryptflags2encryptflags(flags),
-                                       pdp ? pdp->data : 0, cdp ? cdp->data : 0);
+                                       pdp ? pdp->data : nullptr, cdp ? cdp->data : nullptr);
     if (keys) {
         delete[] keys;
     }
@@ -1277,7 +1278,7 @@ Error Context::startCombinedSigningAndEncryption(const std::vector<Key> &recipie
     Data::Private *const cdp = cipherText.impl();
     gpgme_key_t *const keys = getKeysFromRecipients(recipients);
     d->lasterr = gpgme_op_encrypt_sign_start(d->ctx, keys, encryptflags2encryptflags(flags),
-                 pdp ? pdp->data : 0, cdp ? cdp->data : 0);
+                 pdp ? pdp->data : nullptr, cdp ? cdp->data : nullptr);
     if (keys) {
         delete[] keys;
     }
@@ -1294,7 +1295,7 @@ Error Context::createVFS(const char *containerFile, const std::vector< Key > &re
             *keys_it++ = it->impl();
         }
     }
-    *keys_it++ = 0;
+    *keys_it++ = nullptr;
 
     gpgme_error_t op_err;
     d->lasterr = gpgme_op_vfs_create(d->ctx, keys, containerFile, 0, &op_err);
@@ -1662,12 +1663,12 @@ std::ostream &operator<<(std::ostream &os, Context::AuditLogFlags flags)
 
 GpgME::Error GpgME::setDefaultLocale(int cat, const char *val)
 {
-    return Error(gpgme_set_locale(0, cat, val));
+    return Error(gpgme_set_locale(nullptr, cat, val));
 }
 
 GpgME::EngineInfo GpgME::engineInfo(GpgME::Protocol proto)
 {
-    gpgme_engine_info_t ei = 0;
+    gpgme_engine_info_t ei = nullptr;
     if (gpgme_get_engine_info(&ei)) {
         return EngineInfo();
     }
@@ -1718,7 +1719,7 @@ static gpgme_protocol_t engine2protocol(const GpgME::Engine engine)
 
 GpgME::EngineInfo GpgME::engineInfo(GpgME::Engine engine)
 {
-    gpgme_engine_info_t ei = 0;
+    gpgme_engine_info_t ei = nullptr;
     if (gpgme_get_engine_info(&ei)) {
         return EngineInfo();
     }
diff --git a/lang/cpp/src/context.h b/lang/cpp/src/context.h
index d3700e03..b6b902a9 100644
--- a/lang/cpp/src/context.h
+++ b/lang/cpp/src/context.h
@@ -70,7 +70,7 @@ public:
     static Context *createForProtocol(Protocol proto);
     /** Same as above but returning a unique ptr. */
     static std::unique_ptr<Context> create(Protocol proto);
-    static std::unique_ptr<Context> createForEngine(Engine engine, Error *err = 0);
+    static std::unique_ptr<Context> createForEngine(Engine engine, Error *err = nullptr);
     virtual ~Context();
 
     //
@@ -161,7 +161,7 @@ public:
     // Key Listing
     //
 
-    GpgME::Error startKeyListing(const char *pattern = 0, bool secretOnly = false);
+    GpgME::Error startKeyListing(const char *pattern = nullptr, bool secretOnly = false);
     GpgME::Error startKeyListing(const char *patterns[], bool secretOnly = false);
 
     Key nextKey(GpgME::Error &e);
diff --git a/lang/cpp/src/context_p.h b/lang/cpp/src/context_p.h
index 6b0a0805..491e7f77 100644
--- a/lang/cpp/src/context_p.h
+++ b/lang/cpp/src/context_p.h
@@ -69,7 +69,7 @@ public:
         EndMarker
     };
 
-    Private(gpgme_ctx_t c = 0);
+    Private(gpgme_ctx_t c = nullptr);
     ~Private();
 
     gpgme_ctx_t ctx;
diff --git a/lang/cpp/src/context_vanilla.cpp b/lang/cpp/src/context_vanilla.cpp
index 60ddea20..1d7d14d5 100644
--- a/lang/cpp/src/context_vanilla.cpp
+++ b/lang/cpp/src/context_vanilla.cpp
@@ -30,10 +30,10 @@
 
 GIOChannel *GpgME::getGIOChannel(int)
 {
-    return 0;
+    return nullptr;
 }
 
 QIODevice *GpgME::getQIODevice(int)
 {
-    return 0;
+    return nullptr;
 }
diff --git a/lang/cpp/src/data.cpp b/lang/cpp/src/data.cpp
index 2782aa79..547ec76e 100644
--- a/lang/cpp/src/data.cpp
+++ b/lang/cpp/src/data.cpp
@@ -48,11 +48,11 @@ GpgME::Data::Data()
 {
     gpgme_data_t data;
     const gpgme_error_t e = gpgme_data_new(&data);
-    d.reset(new Private(e ? 0 : data));
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(const Null &)
-    : d(new Private(0))
+    : d(new Private(nullptr))
 {
 
 }
@@ -70,14 +70,14 @@ GpgME::Data::Data(const char *buffer, size_t size, bool copy)
     std::string sizestr = std::to_string(size);
     // Ignore errors as this is optional
     gpgme_data_set_flag(data, "size-hint", sizestr.c_str());
-    d.reset(new Private(e ? 0 : data));
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(const char *filename)
 {
     gpgme_data_t data;
     const gpgme_error_t e = gpgme_data_new(&data);
-    d.reset(new Private(e ? 0 : data));
+    d.reset(new Private(e ? nullptr : data));
     if (!e) {
         setFileName(filename);
     }
@@ -86,29 +86,29 @@ GpgME::Data::Data(const char *filename)
 GpgME::Data::Data(const char *filename, off_t offset, size_t length)
 {
     gpgme_data_t data;
-    const gpgme_error_t e = gpgme_data_new_from_filepart(&data, filename, 0, offset, length);
-    d.reset(new Private(e ? 0 : data));
+    const gpgme_error_t e = gpgme_data_new_from_filepart(&data, filename, nullptr, offset, length);
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(FILE *fp)
 {
     gpgme_data_t data;
     const gpgme_error_t e = gpgme_data_new_from_stream(&data, fp);
-    d.reset(new Private(e ? 0 : data));
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(FILE *fp, off_t offset, size_t length)
 {
     gpgme_data_t data;
-    const gpgme_error_t e = gpgme_data_new_from_filepart(&data, 0, fp, offset, length);
-    d.reset(new Private(e ? 0 : data));
+    const gpgme_error_t e = gpgme_data_new_from_filepart(&data, nullptr, fp, offset, length);
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(int fd)
 {
     gpgme_data_t data;
     const gpgme_error_t e = gpgme_data_new_from_fd(&data, fd);
-    d.reset(new Private(e ? 0 : data));
+    d.reset(new Private(e ? nullptr : data));
 }
 
 GpgME::Data::Data(DataProvider *dp)
@@ -118,20 +118,20 @@ GpgME::Data::Data(DataProvider *dp)
         return;
     }
     if (!dp->isSupported(DataProvider::Read)) {
-        d->cbs.read = 0;
+        d->cbs.read = nullptr;
     }
     if (!dp->isSupported(DataProvider::Write)) {
-        d->cbs.write = 0;
+        d->cbs.write = nullptr;
     }
     if (!dp->isSupported(DataProvider::Seek)) {
-        d->cbs.seek = 0;
+        d->cbs.seek = nullptr;
     }
     if (!dp->isSupported(DataProvider::Release)) {
-        d->cbs.release = 0;
+        d->cbs.release = nullptr;
     }
     const gpgme_error_t e = gpgme_data_new_from_cbs(&d->data, &d->cbs, dp);
     if (e) {
-        d->data = 0;
+        d->data = nullptr;
     }
     if (dp->isSupported(DataProvider::Seek)) {
         off_t size = seek(0, SEEK_END);
diff --git a/lang/cpp/src/data_p.h b/lang/cpp/src/data_p.h
index 493b7542..b52940c6 100644
--- a/lang/cpp/src/data_p.h
+++ b/lang/cpp/src/data_p.h
@@ -31,7 +31,7 @@
 class GpgME::Data::Private
 {
 public:
-    explicit Private(gpgme_data_t d = 0)
+    explicit Private(gpgme_data_t d = nullptr)
         : data(d), cbs(data_provider_callbacks) {}
     ~Private();
 
diff --git a/lang/cpp/src/decryptionresult.cpp b/lang/cpp/src/decryptionresult.cpp
index ea0a8a5c..f78cf1d3 100644
--- a/lang/cpp/src/decryptionresult.cpp
+++ b/lang/cpp/src/decryptionresult.cpp
@@ -59,22 +59,22 @@ public:
         for (gpgme_recipient_t r = res.recipients ; r ; r = r->next) {
             recipients.push_back(*r);
         }
-        res.recipients = 0;
+        res.recipients = nullptr;
     }
     ~Private()
     {
         if (res.unsupported_algorithm) {
             std::free(res.unsupported_algorithm);
         }
-        res.unsupported_algorithm = 0;
+        res.unsupported_algorithm = nullptr;
         if (res.file_name) {
             std::free(res.file_name);
         }
-        res.file_name = 0;
+        res.file_name = nullptr;
         if (res.symkey_algo) {
             std::free(res.symkey_algo);
         }
-        res.symkey_algo = 0;
+        res.symkey_algo = nullptr;
     }
 
     _gpgme_op_decrypt_result res;
@@ -109,7 +109,7 @@ make_standard_stuff(DecryptionResult)
 
 const char *GpgME::DecryptionResult::unsupportedAlgorithm() const
 {
-    return d ? d->res.unsupported_algorithm : 0 ;
+    return d ? d->res.unsupported_algorithm : nullptr ;
 }
 
 bool GpgME::DecryptionResult::isWrongKeyUsage() const
@@ -124,7 +124,7 @@ bool GpgME::DecryptionResult::isDeVs() const
 
 const char *GpgME::DecryptionResult::fileName() const
 {
-    return d ? d->res.file_name : 0 ;
+    return d ? d->res.file_name : nullptr ;
 }
 
 unsigned int GpgME::DecryptionResult::numRecipients() const
@@ -208,7 +208,7 @@ const char *GpgME::DecryptionResult::Recipient::keyID() const
     if (d) {
         return d->_keyid;
     }
-    return 0;
+    return nullptr;
 }
 
 const char *GpgME::DecryptionResult::Recipient::shortKeyID() const
@@ -217,7 +217,7 @@ const char *GpgME::DecryptionResult::Recipient::shortKeyID() const
     if (d) {
         return d->_keyid + 8;
     }
-    return 0;
+    return nullptr;
 }
 
 unsigned int GpgME::DecryptionResult::Recipient::publicKeyAlgorithm() const
@@ -233,7 +233,7 @@ const char *GpgME::DecryptionResult::Recipient::publicKeyAlgorithmAsString() con
     if (d) {
         return gpgme_pubkey_algo_name(d->pubkey_algo);
     }
-    return 0;
+    return nullptr;
 }
 
 GpgME::Error GpgME::DecryptionResult::Recipient::status() const
diff --git a/lang/cpp/src/defaultassuantransaction.h b/lang/cpp/src/defaultassuantransaction.h
index f294ffe2..5462f5f2 100644
--- a/lang/cpp/src/defaultassuantransaction.h
+++ b/lang/cpp/src/defaultassuantransaction.h
@@ -53,9 +53,9 @@ public:
     }
 
 private:
-    /* reimp */ Error data(const char *data, size_t datalen);
-    /* reimp */ Data inquire(const char *name, const char *args, Error &err);
-    /* reimp */ Error status(const char *status, const char *args);
+    Error data(const char *data, size_t datalen) override;
+    Data inquire(const char *name, const char *args, Error &err) override;
+    Error status(const char *status, const char *args) override;
 
 private:
     std::vector< std::pair<std::string, std::string> > m_status;
diff --git a/lang/cpp/src/editinteractor.cpp b/lang/cpp/src/editinteractor.cpp
index 3e294889..f7c994a4 100644
--- a/lang/cpp/src/editinteractor.cpp
+++ b/lang/cpp/src/editinteractor.cpp
@@ -176,7 +176,7 @@ EditInteractor::Private::Private(EditInteractor *qq)
     : q(qq),
       state(StartState),
       error(),
-      debug(0)
+      debug(nullptr)
 {
 
 }
diff --git a/lang/cpp/src/encryptionresult.cpp b/lang/cpp/src/encryptionresult.cpp
index 33365cd4..95dcb22e 100644
--- a/lang/cpp/src/encryptionresult.cpp
+++ b/lang/cpp/src/encryptionresult.cpp
@@ -53,7 +53,7 @@ public:
             if (ik->fpr) {
                 copy->fpr = strdup(ik->fpr);
             }
-            copy->next = 0;
+            copy->next = nullptr;
             invalid.push_back(copy);
         }
     }
@@ -61,7 +61,7 @@ public:
     {
         for (std::vector<gpgme_invalid_key_t>::iterator it = invalid.begin() ; it != invalid.end() ; ++it) {
             std::free((*it)->fpr);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
         }
     }
 
@@ -132,7 +132,7 @@ bool GpgME::InvalidRecipient::isNull() const
 
 const char *GpgME::InvalidRecipient::fingerprint() const
 {
-    return isNull() ? 0 : d->invalid[idx]->fpr ;
+    return isNull() ? nullptr : d->invalid[idx]->fpr ;
 }
 
 GpgME::Error GpgME::InvalidRecipient::reason() const
diff --git a/lang/cpp/src/engineinfo.cpp b/lang/cpp/src/engineinfo.cpp
index 1a66ced2..c4ad5300 100644
--- a/lang/cpp/src/engineinfo.cpp
+++ b/lang/cpp/src/engineinfo.cpp
@@ -33,10 +33,10 @@
 class GpgME::EngineInfo::Private
 {
 public:
-    Private(gpgme_engine_info_t engine = 0) : info(engine) {}
+    Private(gpgme_engine_info_t engine = nullptr) : info(engine) {}
     ~Private()
     {
-        info = 0;
+        info = nullptr;
     }
 
     gpgme_engine_info_t info;
@@ -70,12 +70,12 @@ GpgME::Protocol GpgME::EngineInfo::protocol() const
 
 const char *GpgME::EngineInfo::fileName() const
 {
-    return isNull() ? 0 : d->info->file_name;
+    return isNull() ? nullptr : d->info->file_name;
 }
 
 const char *GpgME::EngineInfo::version() const
 {
-    return isNull() ? 0 : d->info->version;
+    return isNull() ? nullptr : d->info->version;
 }
 
 GpgME::EngineInfo::Version GpgME::EngineInfo::engineVersion() const
@@ -85,10 +85,10 @@ GpgME::EngineInfo::Version GpgME::EngineInfo::engineVersion() const
 
 const char *GpgME::EngineInfo::requiredVersion() const
 {
-    return isNull() ? 0 : d->info->req_version;
+    return isNull() ? nullptr : d->info->req_version;
 }
 
 const char *GpgME::EngineInfo::homeDirectory() const
 {
-    return isNull() ? 0 : d->info->home_dir;
+    return isNull() ? nullptr : d->info->home_dir;
 }
diff --git a/lang/cpp/src/eventloopinteractor.cpp b/lang/cpp/src/eventloopinteractor.cpp
index a30b793c..09710ad4 100644
--- a/lang/cpp/src/eventloopinteractor.cpp
+++ b/lang/cpp/src/eventloopinteractor.cpp
@@ -77,10 +77,10 @@ public:
 
 const gpgme_io_cbs EventLoopInteractor::Private::iocbs = {
     &EventLoopInteractor::Private::registerIOCb,
-    0,
+    nullptr,
     &EventLoopInteractor::Private::removeIOCb,
     &EventLoopInteractor::Private::eventIOCb,
-    0
+    nullptr
 };
 
 //
@@ -114,7 +114,7 @@ void EventLoopInteractor::Private::removeIOCb(void *tag)
             it != instance()->d->mCallbacks.end() ; ++it) {
         if (*it == tag) {
             instance()->unregisterWatcher((*it)->externalTag);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
             instance()->d->mCallbacks.erase(it);
             return;
         }
@@ -159,7 +159,7 @@ void EventLoopInteractor::Private::eventIOCb(void *data, gpgme_event_io_t type,
 // EventLoopInteractor Implementation
 //
 
-EventLoopInteractor *EventLoopInteractor::mSelf = 0;
+EventLoopInteractor *EventLoopInteractor::mSelf = nullptr;
 
 EventLoopInteractor::EventLoopInteractor() : d(new Private)
 {
@@ -170,7 +170,7 @@ EventLoopInteractor::EventLoopInteractor() : d(new Private)
 EventLoopInteractor::~EventLoopInteractor()
 {
     // warn if there are still callbacks registered
-    mSelf = 0;
+    mSelf = nullptr;
     delete d;
 }
 
diff --git a/lang/cpp/src/global.h b/lang/cpp/src/global.h
index e303c49a..9760e215 100644
--- a/lang/cpp/src/global.h
+++ b/lang/cpp/src/global.h
@@ -165,7 +165,7 @@ GPGMEPP_EXPORT bool hasFeature(unsigned long feature, unsigned long feature2);
     struct __safe_bool_dummy__ { void nonnull() {} }; \
     typedef void ( __safe_bool_dummy__::*unspecified_bool_type )(); \
     public: \
-    operator unspecified_bool_type() const { return ( Cond ) ? &__safe_bool_dummy__::nonnull : 0 ; }
+    operator unspecified_bool_type() const { return ( Cond ) ? &__safe_bool_dummy__::nonnull : nullptr; }
 # endif
 
 inline int _gpgmepp_strcmp(const char *s1, const char *s2)
diff --git a/lang/cpp/src/gpgadduserideditinteractor.cpp b/lang/cpp/src/gpgadduserideditinteractor.cpp
index 593ac58e..c26f5593 100644
--- a/lang/cpp/src/gpgadduserideditinteractor.cpp
+++ b/lang/cpp/src/gpgadduserideditinteractor.cpp
@@ -105,10 +105,10 @@ const char *GpgAddUserIDEditInteractor::action(Error &err) const
         return "Y";
     case START:
     case ERROR:
-        return 0;
+        return nullptr;
     default:
         err = Error::fromCode(GPG_ERR_GENERAL);
-        return 0;
+        return nullptr;
     }
 }
 
diff --git a/lang/cpp/src/gpgadduserideditinteractor.h b/lang/cpp/src/gpgadduserideditinteractor.h
index 10cac08d..9d06f994 100644
--- a/lang/cpp/src/gpgadduserideditinteractor.h
+++ b/lang/cpp/src/gpgadduserideditinteractor.h
@@ -57,8 +57,8 @@ public:
     }
 
 private:
-    /* reimp */ const char *action(Error &err) const;
-    /* reimp */ unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const;
+    const char *action(Error &err) const override;
+    unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const override;
 
 private:
     std::string m_name, m_email, m_comment;
diff --git a/lang/cpp/src/gpgagentgetinfoassuantransaction.h b/lang/cpp/src/gpgagentgetinfoassuantransaction.h
index 1bc50161..bbb5776b 100644
--- a/lang/cpp/src/gpgagentgetinfoassuantransaction.h
+++ b/lang/cpp/src/gpgagentgetinfoassuantransaction.h
@@ -56,10 +56,10 @@ public:
     std::string sshSocketName() const;
 
 private:
-    /* reimp */ const char *command() const;
-    /* reimp */ Error data(const char *data, size_t datalen);
-    /* reimp */ Data inquire(const char *name, const char *args, Error &err);
-    /* reimp */ Error status(const char *status, const char *args);
+    const char *command() const;
+    Error data(const char *data, size_t datalen) override;
+    Data inquire(const char *name, const char *args, Error &err) override;
+    Error status(const char *status, const char *args) override;
 
 private:
     void makeCommand() const;
diff --git a/lang/cpp/src/gpggencardkeyinteractor.cpp b/lang/cpp/src/gpggencardkeyinteractor.cpp
index 0ed6781a..831e4c4a 100644
--- a/lang/cpp/src/gpggencardkeyinteractor.cpp
+++ b/lang/cpp/src/gpggencardkeyinteractor.cpp
@@ -143,10 +143,10 @@ const char *GpgGenCardKeyInteractor::action(Error &err) const
     case GOT_SERIAL:
     case BACKUP_KEY_CREATED:
     case ERROR:
-        return 0;
+        return nullptr;
     default:
         err = Error::fromCode(GPG_ERR_GENERAL);
-        return 0;
+        return nullptr;
     }
 }
 
diff --git a/lang/cpp/src/gpggencardkeyinteractor.h b/lang/cpp/src/gpggencardkeyinteractor.h
index 7cc22168..d6a7b7b0 100644
--- a/lang/cpp/src/gpggencardkeyinteractor.h
+++ b/lang/cpp/src/gpggencardkeyinteractor.h
@@ -59,8 +59,8 @@ public:
     std::string backupFileName() const;
 
 private:
-    /* reimp */ const char *action(Error &err) const;
-    /* reimp */ unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const;
+    const char *action(Error &err) const override;
+    unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const override;
 
 private:
     class Private;
diff --git a/lang/cpp/src/gpgsetexpirytimeeditinteractor.cpp b/lang/cpp/src/gpgsetexpirytimeeditinteractor.cpp
index 7aebe73a..2936d194 100644
--- a/lang/cpp/src/gpgsetexpirytimeeditinteractor.cpp
+++ b/lang/cpp/src/gpgsetexpirytimeeditinteractor.cpp
@@ -81,10 +81,10 @@ const char *GpgSetExpiryTimeEditInteractor::action(Error &err) const
         return "Y";
     case START:
     case ERROR:
-        return 0;
+        return nullptr;
     default:
         err = Error::fromCode(GPG_ERR_GENERAL);
-        return 0;
+        return nullptr;
     }
 }
 
diff --git a/lang/cpp/src/gpgsetexpirytimeeditinteractor.h b/lang/cpp/src/gpgsetexpirytimeeditinteractor.h
index 6a4c7373..6c96b214 100644
--- a/lang/cpp/src/gpgsetexpirytimeeditinteractor.h
+++ b/lang/cpp/src/gpgsetexpirytimeeditinteractor.h
@@ -39,8 +39,8 @@ public:
     ~GpgSetExpiryTimeEditInteractor();
 
 private:
-    /* reimp */ const char *action(Error &err) const;
-    /* reimp */ unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const;
+    const char *action(Error &err) const override;
+    unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const override;
 
 private:
     const std::string m_strtime;
diff --git a/lang/cpp/src/gpgsetownertrusteditinteractor.cpp b/lang/cpp/src/gpgsetownertrusteditinteractor.cpp
index 7525fd82..f1e99ea9 100644
--- a/lang/cpp/src/gpgsetownertrusteditinteractor.cpp
+++ b/lang/cpp/src/gpgsetownertrusteditinteractor.cpp
@@ -85,10 +85,10 @@ const char *GpgSetOwnerTrustEditInteractor::action(Error &err) const
         return "Y";
     case START:
     case ERROR:
-        return 0;
+        return nullptr;
     default:
         err = Error::fromCode(GPG_ERR_GENERAL);
-        return 0;
+        return nullptr;
     }
 }
 
diff --git a/lang/cpp/src/gpgsetownertrusteditinteractor.h b/lang/cpp/src/gpgsetownertrusteditinteractor.h
index 9cec77e7..b7f920be 100644
--- a/lang/cpp/src/gpgsetownertrusteditinteractor.h
+++ b/lang/cpp/src/gpgsetownertrusteditinteractor.h
@@ -40,8 +40,8 @@ public:
     ~GpgSetOwnerTrustEditInteractor();
 
 private:
-    /* reimp */ const char *action(Error &err) const;
-    /* reimp */ unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const;
+    const char *action(Error &err) const override;
+    unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const override;
 
 private:
     const Key::OwnerTrust m_ownertrust;
diff --git a/lang/cpp/src/gpgsignkeyeditinteractor.cpp b/lang/cpp/src/gpgsignkeyeditinteractor.cpp
index 79691bc2..295802db 100644
--- a/lang/cpp/src/gpgsignkeyeditinteractor.cpp
+++ b/lang/cpp/src/gpgsignkeyeditinteractor.cpp
@@ -233,7 +233,7 @@ const char *GpgSignKeyEditInteractor::action(Error &err) const
     //TODO
     case SET_TRUST_REGEXP:
         //TODO
-        return 0;
+        return nullptr;
     case SET_CHECK_LEVEL:
         return check_level_strings[d->checkLevel];
     case CONFIRM2:
@@ -253,7 +253,7 @@ const char *GpgSignKeyEditInteractor::action(Error &err) const
     // fall through
     case ERROR:
         err = Error::fromCode(GPG_ERR_GENERAL);
-        return 0;
+        return nullptr;
     }
 }
 
diff --git a/lang/cpp/src/gpgsignkeyeditinteractor.h b/lang/cpp/src/gpgsignkeyeditinteractor.h
index f6cb4737..34b1f064 100644
--- a/lang/cpp/src/gpgsignkeyeditinteractor.h
+++ b/lang/cpp/src/gpgsignkeyeditinteractor.h
@@ -53,8 +53,8 @@ public:
     void setSigningOptions(int options);
 
 private:
-    /* reimp */ const char *action(Error &err) const;
-    /* reimp */ unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const;
+    const char *action(Error &err) const override;
+    unsigned int nextState(unsigned int statusCode, const char *args, Error &err) const override;
 
 private:
     class Private;
diff --git a/lang/cpp/src/importresult.cpp b/lang/cpp/src/importresult.cpp
index dbb31d05..05943ca0 100644
--- a/lang/cpp/src/importresult.cpp
+++ b/lang/cpp/src/importresult.cpp
@@ -46,16 +46,16 @@ public:
         for (gpgme_import_status_t is = r.imports ; is ; is = is->next) {
             gpgme_import_status_t copy = new _gpgme_import_status(*is);
             copy->fpr = strdup(is->fpr);
-            copy->next = 0;
+            copy->next = nullptr;
             imports.push_back(copy);
         }
-        res.imports = 0;
+        res.imports = nullptr;
     }
     ~Private()
     {
         for (std::vector<gpgme_import_status_t>::iterator it = imports.begin() ; it != imports.end() ; ++it) {
             std::free((*it)->fpr);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
         }
     }
 
@@ -192,7 +192,7 @@ bool GpgME::Import::isNull() const
 
 const char *GpgME::Import::fingerprint() const
 {
-    return isNull() ? 0 : d->imports[idx]->fpr ;
+    return isNull() ? nullptr : d->imports[idx]->fpr ;
 }
 
 GpgME::Error GpgME::Import::error() const
diff --git a/lang/cpp/src/key.cpp b/lang/cpp/src/key.cpp
index 0d272926..4638fd86 100644
--- a/lang/cpp/src/key.cpp
+++ b/lang/cpp/src/key.cpp
@@ -165,7 +165,7 @@ Protocol Key::protocol() const
 
 const char *Key::protocolAsString() const
 {
-    return key ? gpgme_get_protocol_name(key->protocol) : 0 ;
+    return key ? gpgme_get_protocol_name(key->protocol) : nullptr ;
 }
 
 bool Key::isRevoked() const
@@ -252,26 +252,26 @@ bool Key::isDeVs() const
 
 const char *Key::issuerSerial() const
 {
-    return key ? key->issuer_serial : 0 ;
+    return key ? key->issuer_serial : nullptr ;
 }
 const char *Key::issuerName() const
 {
-    return key ? key->issuer_name : 0 ;
+    return key ? key->issuer_name : nullptr ;
 }
 const char *Key::chainID() const
 {
-    return key ? key->chain_id : 0 ;
+    return key ? key->chain_id : nullptr ;
 }
 
 const char *Key::keyID() const
 {
-    return key && key->subkeys ? key->subkeys->keyid : 0 ;
+    return key && key->subkeys ? key->subkeys->keyid : nullptr ;
 }
 
 const char *Key::shortKeyID() const
 {
     if (!key || !key->subkeys || !key->subkeys->keyid) {
-        return 0;
+        return nullptr;
     }
     const int len = strlen(key->subkeys->keyid);
     if (len > 8) {
@@ -299,7 +299,7 @@ const char *Key::primaryFingerprint() const
 
 unsigned int Key::keyListMode() const
 {
-    return key ? convert_from_gpgme_keylist_mode_t(key->keylist_mode) : 0 ;
+    return key ? convert_from_gpgme_keylist_mode_t(key->keylist_mode) : 0;
 }
 
 const Key &Key::mergeWith(const Key &other)
@@ -410,7 +410,7 @@ gpgme_sub_key_t find_subkey(const shared_gpgme_key_t &key, unsigned int idx)
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
 gpgme_sub_key_t verify_subkey(const shared_gpgme_key_t &key, gpgme_sub_key_t subkey)
@@ -422,10 +422,10 @@ gpgme_sub_key_t verify_subkey(const shared_gpgme_key_t &key, gpgme_sub_key_t sub
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
-Subkey::Subkey() : key(), subkey(0) {}
+Subkey::Subkey() : key(), subkey(nullptr) {}
 
 Subkey::Subkey(const shared_gpgme_key_t &k, unsigned int idx)
     : key(k), subkey(find_subkey(k, idx))
@@ -446,12 +446,12 @@ Key Subkey::parent() const
 
 const char *Subkey::keyID() const
 {
-    return subkey ? subkey->keyid : 0 ;
+    return subkey ? subkey->keyid : nullptr ;
 }
 
 const char *Subkey::fingerprint() const
 {
-    return subkey ? subkey->fpr : 0 ;
+    return subkey ? subkey->fpr : nullptr ;
 }
 
 Subkey::PubkeyAlgo Subkey::publicKeyAlgorithm() const
@@ -589,7 +589,7 @@ gpgme_user_id_t find_uid(const shared_gpgme_key_t &key, unsigned int idx)
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
 gpgme_user_id_t verify_uid(const shared_gpgme_key_t &key, gpgme_user_id_t uid)
@@ -601,10 +601,10 @@ gpgme_user_id_t verify_uid(const shared_gpgme_key_t &key, gpgme_user_id_t uid)
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
-UserID::UserID() : key(), uid(0) {}
+UserID::UserID() : key(), uid(nullptr) {}
 
 UserID::UserID(const shared_gpgme_key_t &k, gpgme_user_id_t u)
     : key(k), uid(verify_uid(k, u))
@@ -656,22 +656,22 @@ std::vector<UserID::Signature> UserID::signatures() const
 
 const char *UserID::id() const
 {
-    return uid ? uid->uid : 0 ;
+    return uid ? uid->uid : nullptr ;
 }
 
 const char *UserID::name() const
 {
-    return uid ? uid->name : 0 ;
+    return uid ? uid->name : nullptr ;
 }
 
 const char *UserID::email() const
 {
-    return uid ? uid->email : 0 ;
+    return uid ? uid->email : nullptr ;
 }
 
 const char *UserID::comment() const
 {
-    return uid ? uid->comment : 0 ;
+    return uid ? uid->comment : nullptr ;
 }
 
 UserID::Validity UserID::validity() const
@@ -739,7 +739,7 @@ gpgme_key_sig_t find_signature(gpgme_user_id_t uid, unsigned int idx)
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
 gpgme_key_sig_t verify_signature(gpgme_user_id_t uid, gpgme_key_sig_t sig)
@@ -751,10 +751,10 @@ gpgme_key_sig_t verify_signature(gpgme_user_id_t uid, gpgme_key_sig_t sig)
             }
         }
     }
-    return 0;
+    return nullptr;
 }
 
-UserID::Signature::Signature() : key(), uid(0), sig(0) {}
+UserID::Signature::Signature() : key(), uid(nullptr), sig(nullptr) {}
 
 UserID::Signature::Signature(const shared_gpgme_key_t &k, gpgme_user_id_t u, unsigned int idx)
     : key(k), uid(verify_uid(k, u)), sig(find_signature(uid, idx))
@@ -775,7 +775,7 @@ UserID UserID::Signature::parent() const
 
 const char *UserID::Signature::signerKeyID() const
 {
-    return sig ? sig->keyid : 0 ;
+    return sig ? sig->keyid : nullptr ;
 }
 
 const char *UserID::Signature::algorithmAsString() const
@@ -825,22 +825,22 @@ bool UserID::Signature::isExportable() const
 
 const char *UserID::Signature::signerUserID() const
 {
-    return sig ? sig->uid : 0 ;
+    return sig ? sig->uid : nullptr ;
 }
 
 const char *UserID::Signature::signerName() const
 {
-    return sig ? sig->name : 0 ;
+    return sig ? sig->name : nullptr ;
 }
 
 const char *UserID::Signature::signerEmail() const
 {
-    return sig ? sig->email : 0 ;
+    return sig ? sig->email : nullptr ;
 }
 
 const char *UserID::Signature::signerComment() const
 {
-    return sig ? sig->comment : 0 ;
+    return sig ? sig->comment : nullptr ;
 }
 
 unsigned int UserID::Signature::certClass() const
@@ -923,14 +923,14 @@ std::vector<Notation> UserID::Signature::notations() const
 const char *UserID::Signature::policyURL() const
 {
     if (!sig) {
-        return 0;
+        return nullptr;
     }
     for (gpgme_sig_notation_t nota = sig->notations ; nota ; nota = nota->next) {
         if (!nota->name) {
             return nota->value;
         }
     }
-    return 0;
+    return nullptr;
 }
 
 std::string UserID::addrSpecFromString(const char *userid)
diff --git a/lang/cpp/src/keygenerationresult.cpp b/lang/cpp/src/keygenerationresult.cpp
index ebbb3b99..49342f42 100644
--- a/lang/cpp/src/keygenerationresult.cpp
+++ b/lang/cpp/src/keygenerationresult.cpp
@@ -50,7 +50,7 @@ public:
         if (res.fpr) {
             std::free(res.fpr);
         }
-        res.fpr = 0;
+        res.fpr = nullptr;
     }
 
     _gpgme_op_genkey_result res;
@@ -94,5 +94,5 @@ bool GpgME::KeyGenerationResult::isSubkeyGenerated() const
 
 const char *GpgME::KeyGenerationResult::fingerprint() const
 {
-    return d ? d->res.fpr : 0 ;
+    return d ? d->res.fpr : nullptr ;
 }
diff --git a/lang/cpp/src/scdgetinfoassuantransaction.h b/lang/cpp/src/scdgetinfoassuantransaction.h
index ef805303..621725e4 100644
--- a/lang/cpp/src/scdgetinfoassuantransaction.h
+++ b/lang/cpp/src/scdgetinfoassuantransaction.h
@@ -59,10 +59,10 @@ public:
     std::vector<std::string> applicationList() const;
 
 private:
-    /* reimp */ const char *command() const;
-    /* reimp */ Error data(const char *data, size_t datalen);
-    /* reimp */ Data inquire(const char *name, const char *args, Error &err);
-    /* reimp */ Error status(const char *status, const char *args);
+    const char *command() const;
+    Error data(const char *data, size_t datalen) override;
+    Data inquire(const char *name, const char *args, Error &err) override;
+    Error status(const char *status, const char *args) override;
 
 private:
     void makeCommand() const;
diff --git a/lang/cpp/src/signingresult.cpp b/lang/cpp/src/signingresult.cpp
index 6a5231ff..6e0dd90a 100644
--- a/lang/cpp/src/signingresult.cpp
+++ b/lang/cpp/src/signingresult.cpp
@@ -53,7 +53,7 @@ public:
             if (is->fpr) {
                 copy->fpr = strdup(is->fpr);
             }
-            copy->next = 0;
+            copy->next = nullptr;
             created.push_back(copy);
         }
         for (gpgme_invalid_key_t ik = r->invalid_signers ; ik ; ik = ik->next) {
@@ -61,7 +61,7 @@ public:
             if (ik->fpr) {
                 copy->fpr = strdup(ik->fpr);
             }
-            copy->next = 0;
+            copy->next = nullptr;
             invalid.push_back(copy);
         }
     }
@@ -69,11 +69,11 @@ public:
     {
         for (std::vector<gpgme_new_signature_t>::iterator it = created.begin() ; it != created.end() ; ++it) {
             std::free((*it)->fpr);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
         }
         for (std::vector<gpgme_invalid_key_t>::iterator it = invalid.begin() ; it != invalid.end() ; ++it) {
             std::free((*it)->fpr);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
         }
     }
 
@@ -158,7 +158,7 @@ bool GpgME::InvalidSigningKey::isNull() const
 
 const char *GpgME::InvalidSigningKey::fingerprint() const
 {
-    return isNull() ? 0 : d->invalid[idx]->fpr ;
+    return isNull() ? nullptr : d->invalid[idx]->fpr ;
 }
 
 GpgME::Error GpgME::InvalidSigningKey::reason() const
@@ -181,7 +181,7 @@ bool GpgME::CreatedSignature::isNull() const
 
 const char *GpgME::CreatedSignature::fingerprint() const
 {
-    return isNull() ? 0 : d->created[idx]->fpr ;
+    return isNull() ? nullptr : d->created[idx]->fpr ;
 }
 
 time_t GpgME::CreatedSignature::creationTime() const
diff --git a/lang/cpp/src/trustitem.cpp b/lang/cpp/src/trustitem.cpp
index c29c0f41..4302f657 100644
--- a/lang/cpp/src/trustitem.cpp
+++ b/lang/cpp/src/trustitem.cpp
@@ -67,7 +67,7 @@ TrustItem::~TrustItem()
     if (d->item) {
         gpgme_trust_item_unref(d->item);
     }
-    delete d; d = 0;
+    delete d; d = nullptr;
 }
 
 bool TrustItem::isNull() const
@@ -82,22 +82,22 @@ gpgme_trust_item_t TrustItem::impl() const
 
 const char *TrustItem::keyID() const
 {
-    return d->item ? d->item->keyid : 0 ;
+    return d->item ? d->item->keyid : nullptr ;
 }
 
 const char *TrustItem::userID() const
 {
-    return d->item ? d->item->name : 0 ;
+    return d->item ? d->item->name : nullptr ;
 }
 
 const char *TrustItem::ownerTrustAsString() const
 {
-    return d->item ? d->item->owner_trust : 0 ;
+    return d->item ? d->item->owner_trust : nullptr ;
 }
 
 const char *TrustItem::validityAsString() const
 {
-    return d->item ? d->item->validity : 0 ;
+    return d->item ? d->item->validity : nullptr ;
 }
 
 int TrustItem::trustLevel() const
diff --git a/lang/cpp/src/trustitem.h b/lang/cpp/src/trustitem.h
index ad2a4a61..d31dc0b7 100644
--- a/lang/cpp/src/trustitem.h
+++ b/lang/cpp/src/trustitem.h
@@ -41,7 +41,7 @@ class GPGMEPP_EXPORT TrustItem
 {
     friend class ::GpgME::Context;
 public:
-    explicit TrustItem(gpgme_trust_item_t item = 0);
+    explicit TrustItem(gpgme_trust_item_t item = nullptr);
     TrustItem(const TrustItem &other);
     virtual ~TrustItem();
 
diff --git a/lang/cpp/src/verificationresult.cpp b/lang/cpp/src/verificationresult.cpp
index fa8237ad..1e9f81f5 100644
--- a/lang/cpp/src/verificationresult.cpp
+++ b/lang/cpp/src/verificationresult.cpp
@@ -68,9 +68,9 @@ public:
                 scopy->pka_address = strdup(is->pka_address);
             }
 # else
-            scopy->pka_address = 0;
+            scopy->pka_address = nullptr;
 # endif
-            scopy->next = 0;
+            scopy->next = nullptr;
             sigs.push_back(scopy);
             // copy keys
             if (scopy->key) {
@@ -80,7 +80,7 @@ public:
             }
             // copy notations:
             nota.push_back(std::vector<Nota>());
-            purls.push_back(0);
+            purls.push_back(nullptr);
             for (gpgme_sig_notation_t in = is->notations ; in ; in = in->next) {
                 if (!in->name) {
                     if (in->value) {
@@ -88,7 +88,7 @@ public:
                     }
                     continue;
                 }
-                Nota n = { 0, 0, in->flags };
+                Nota n = { nullptr, nullptr, in->flags };
                 n.name = strdup(in->name);
                 if (in->value) {
                     n.value = strdup(in->value);
@@ -102,12 +102,12 @@ public:
         for (std::vector<gpgme_signature_t>::iterator it = sigs.begin() ; it != sigs.end() ; ++it) {
             std::free((*it)->fpr);
             std::free((*it)->pka_address);
-            delete *it; *it = 0;
+            delete *it; *it = nullptr;
         }
         for (std::vector< std::vector<Nota> >::iterator it = nota.begin() ; it != nota.end() ; ++it) {
             for (std::vector<Nota>::iterator jt = it->begin() ; jt != it->end() ; ++jt) {
-                std::free(jt->name);  jt->name = 0;
-                std::free(jt->value); jt->value = 0;
+                std::free(jt->name);  jt->name = nullptr;
+                std::free(jt->value); jt->value = nullptr;
             }
         }
         std::for_each(purls.begin(), purls.end(), &std::free);
@@ -159,7 +159,7 @@ make_standard_stuff(VerificationResult)
 
 const char *GpgME::VerificationResult::fileName() const
 {
-    return d ? d->file_name.c_str() : 0 ;
+    return d ? d->file_name.c_str() : nullptr ;
 }
 
 unsigned int GpgME::VerificationResult::numSignatures() const
@@ -245,7 +245,7 @@ GpgME::Signature::Summary GpgME::Signature::summary() const
 
 const char *GpgME::Signature::fingerprint() const
 {
-    return isNull() ? 0 : d->sigs[idx]->fpr ;
+    return isNull() ? nullptr : d->sigs[idx]->fpr ;
 }
 
 GpgME::Error GpgME::Signature::status() const
@@ -296,7 +296,7 @@ const char *GpgME::Signature::pkaAddress() const
     if (!isNull()) {
         return d->sigs[idx]->pka_address;
     }
-    return 0;
+    return nullptr;
 }
 
 GpgME::Signature::Validity GpgME::Signature::validity() const
@@ -349,7 +349,7 @@ const char *GpgME::Signature::publicKeyAlgorithmAsString() const
     if (!isNull()) {
         return gpgme_pubkey_algo_name(d->sigs[idx]->pubkey_algo);
     }
-    return 0;
+    return nullptr;
 }
 
 unsigned int GpgME::Signature::hashAlgorithm() const
@@ -365,12 +365,12 @@ const char *GpgME::Signature::hashAlgorithmAsString() const
     if (!isNull()) {
         return gpgme_hash_algo_name(d->sigs[idx]->hash_algo);
     }
-    return 0;
+    return nullptr;
 }
 
 const char *GpgME::Signature::policyURL() const
 {
-    return isNull() ? 0 : d->purls[idx] ;
+    return isNull() ? nullptr : d->purls[idx] ;
 }
 
 GpgME::Notation GpgME::Signature::notation(unsigned int nidx) const
@@ -429,14 +429,14 @@ GpgME::Key GpgME::Signature::key(bool search, bool update) const
 class GpgME::Notation::Private
 {
 public:
-    Private() : d(), sidx(0), nidx(0), nota(0) {}
+    Private() : d(), sidx(0), nidx(0), nota(nullptr) {}
     Private(const std::shared_ptr<VerificationResult::Private> &priv, unsigned int sindex, unsigned int nindex)
-        : d(priv), sidx(sindex), nidx(nindex), nota(0)
+        : d(priv), sidx(sindex), nidx(nindex), nota(nullptr)
     {
 
     }
     Private(gpgme_sig_notation_t n)
-        : d(), sidx(0), nidx(0), nota(n ? new _gpgme_sig_notation(*n) : 0)
+        : d(), sidx(0), nidx(0), nota(n ? new _gpgme_sig_notation(*n) : nullptr)
     {
         if (nota && nota->name) {
             nota->name = strdup(nota->name);
@@ -456,8 +456,8 @@ public:
     ~Private()
     {
         if (nota) {
-            std::free(nota->name);  nota->name = 0;
-            std::free(nota->value); nota->value = 0;
+            std::free(nota->name);  nota->name = nullptr;
+            std::free(nota->value); nota->value = nullptr;
             delete nota;
         }
     }
@@ -495,24 +495,24 @@ bool GpgME::Notation::isNull() const
 const char *GpgME::Notation::name() const
 {
     return
-        isNull() ? 0 :
+        isNull() ? nullptr :
         d->d ? d->d->nota[d->sidx][d->nidx].name :
-        d->nota ? d->nota->name : 0 ;
+        d->nota ? d->nota->name : nullptr ;
 }
 
 const char *GpgME::Notation::value() const
 {
     return
-        isNull() ? 0 :
+        isNull() ? nullptr :
         d->d ? d->d->nota[d->sidx][d->nidx].value :
-        d->nota ? d->nota->value : 0 ;
+        d->nota ? d->nota->value : nullptr ;
 }
 
 GpgME::Notation::Flags GpgME::Notation::flags() const
 {
     return
         convert_from_gpgme_sig_notation_flags_t(
-            isNull() ? 0 :
+            isNull() ? 0:
             d->d ? d->d->nota[d->sidx][d->nidx].flags :
             d->nota ? d->nota->flags : 0);
 }
diff --git a/lang/cpp/src/vfsmountresult.cpp b/lang/cpp/src/vfsmountresult.cpp
index 60faa385..901ccfe2 100644
--- a/lang/cpp/src/vfsmountresult.cpp
+++ b/lang/cpp/src/vfsmountresult.cpp
@@ -40,7 +40,7 @@ using namespace GpgME;
 class VfsMountResult::Private
 {
 public:
-    explicit Private(const gpgme_vfs_mount_result_t r) : mountDir(0)
+    explicit Private(const gpgme_vfs_mount_result_t r) : mountDir(nullptr)
     {
         if (r && r->mount_dir) {
             mountDir = strdup(r->mount_dir);
@@ -81,7 +81,7 @@ const char *VfsMountResult::mountDir() const
     if (d) {
         return d->mountDir;
     }
-    return 0;
+    return nullptr;
 }
 
 std::ostream &GpgME::operator<<(std::ostream &os, const VfsMountResult &result)