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.

19 files changed, 84 insertions, 83 deletions

diff --git a/lang/qt/src/Makefile.am b/lang/qt/src/Makefile.am
index 32251424..80dcde15 100644
--- a/lang/qt/src/Makefile.am
+++ b/lang/qt/src/Makefile.am
@@ -219,7 +219,8 @@ libqgpgme_la_SOURCES = $(qgpgme_sources) $(qgpgme_headers) $(private_qgpgme_head
 
 AM_CPPFLAGS = -I$(top_srcdir)/lang/cpp/src -I$(top_builddir)/src \
               @GPGME_QT_CFLAGS@ @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
-              -DBUILDING_QGPGME
+              -DBUILDING_QGPGME -Wsuggest-override \
+              -Wzero-as-null-pointer-constant
 
 libqgpgme_la_LIBADD = ../../cpp/src/libgpgmepp.la ../../../src/libgpgme.la \
                        @LIBASSUAN_LIBS@ @GPGME_QT_LIBS@
diff --git a/lang/qt/src/cryptoconfig.h b/lang/qt/src/cryptoconfig.h
index d545e597..d7aae9d7 100644
--- a/lang/qt/src/cryptoconfig.h
+++ b/lang/qt/src/cryptoconfig.h
@@ -382,8 +382,8 @@ public:
     CryptoConfigEntry *entry(const QString &componentName, const QString &groupName, const QString &entryName) const
     {
         const QGpgME::CryptoConfigComponent *comp = component(componentName);
-        const QGpgME::CryptoConfigGroup *group = comp ? comp->group(groupName) : 0;
-        return group ? group->entry(entryName) : 0;
+        const QGpgME::CryptoConfigGroup *group = comp ? comp->group(groupName) : nullptr;
+        return group ? group->entry(entryName) : nullptr;
     }
 
     /**
diff --git a/lang/qt/src/dataprovider.h b/lang/qt/src/dataprovider.h
index 980a6a98..636d6fb6 100644
--- a/lang/qt/src/dataprovider.h
+++ b/lang/qt/src/dataprovider.h
@@ -51,14 +51,14 @@ public:
 private:
     // these shall only be accessed through the dataprovider
     // interface, where they're public:
-    bool isSupported(Operation) const
+    bool isSupported(Operation) const override
     {
         return true;
     }
-    ssize_t read(void *buffer, size_t bufSize);
-    ssize_t write(const void *buffer, size_t bufSize);
-    off_t seek(off_t offset, int whence);
-    void release();
+    ssize_t read(void *buffer, size_t bufSize) override;
+    ssize_t write(const void *buffer, size_t bufSize) override;
+    off_t seek(off_t offset, int whence) override;
+    void release() override;
 
 private:
     QByteArray mArray;
@@ -79,11 +79,11 @@ public:
 private:
     // these shall only be accessed through the dataprovider
     // interface, where they're public:
-    bool isSupported(Operation) const;
-    ssize_t read(void *buffer, size_t bufSize);
-    ssize_t write(const void *buffer, size_t bufSize);
-    off_t seek(off_t offset, int whence);
-    void release();
+    bool isSupported(Operation) const override;
+    ssize_t read(void *buffer, size_t bufSize) override;
+    ssize_t write(const void *buffer, size_t bufSize) override;
+    off_t seek(off_t offset, int whence) override;
+    void release() override;
 
 private:
     const std::shared_ptr<QIODevice> mIO;
diff --git a/lang/qt/src/dn.cpp b/lang/qt/src/dn.cpp
index d122333d..e41d481c 100644
--- a/lang/qt/src/dn.cpp
+++ b/lang/qt/src/dn.cpp
@@ -256,7 +256,7 @@ parse_dn(const unsigned char *string)
             break;    /* ready */
         }
 
-        DnPair pair = { 0, 0 };
+        DnPair pair = { nullptr, nullptr };
         string = parse_dn_part(&pair, string);
         if (!string) {
             goto failure;
diff --git a/lang/qt/src/multideletejob.cpp b/lang/qt/src/multideletejob.cpp
index 67f2a78e..c3e6520d 100644
--- a/lang/qt/src/multideletejob.cpp
+++ b/lang/qt/src/multideletejob.cpp
@@ -47,9 +47,9 @@
 #include <assert.h>
 
 QGpgME::MultiDeleteJob::MultiDeleteJob(const Protocol *protocol)
-    : Job(0),
+    : Job(nullptr),
       mProtocol(protocol),
-      mJob(0)
+      mJob(nullptr)
 {
     assert(protocol);
 }
@@ -83,7 +83,7 @@ void QGpgME::MultiDeleteJob::slotCancel()
 
 void QGpgME::MultiDeleteJob::slotResult(const GpgME::Error &err)
 {
-    mJob = 0;
+    mJob = nullptr;
     GpgME::Error error = err;
     if (error ||  // error in last op
             mIt == mKeys.end() || // (shouldn't happen)
diff --git a/lang/qt/src/protocol_p.h b/lang/qt/src/protocol_p.h
index b6d1abfa..57c1ed81 100644
--- a/lang/qt/src/protocol_p.h
+++ b/lang/qt/src/protocol_p.h
@@ -93,14 +93,14 @@ public:
 
     QGpgME::SpecialJob *specialJob(const char *, const QMap<QString, QVariant> &) const Q_DECL_OVERRIDE
     {
-        return 0;
+        return nullptr;
     }
 
     QGpgME::KeyListJob *keyListJob(bool remote, bool includeSigs, bool validate) const Q_DECL_OVERRIDE
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         unsigned int mode = context->keyListMode();
@@ -125,7 +125,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         unsigned int mode = context->keyListMode();
@@ -152,7 +152,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setArmor(armor);
@@ -164,7 +164,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEDecryptJob(context);
     }
@@ -173,7 +173,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setArmor(armor);
@@ -185,7 +185,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setTextMode(textMode);
@@ -196,7 +196,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setTextMode(textMode);
@@ -207,7 +207,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEKeyGenerationJob(context);
     }
@@ -216,7 +216,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEImportJob(context);
     }
@@ -225,7 +225,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEImportFromKeyserverJob(context);
     }
@@ -234,7 +234,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setArmor(armor);
@@ -244,7 +244,7 @@ public:
     QGpgME::ExportJob *secretKeyExportJob(bool armor, const QString &charset) const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::CMS) { // fixme: add support for gpg, too
-            return 0;
+            return nullptr;
         }
 
         // this operation is not supported by gpgme, so we have to call gpgsm ourselves:
@@ -254,7 +254,7 @@ public:
     QGpgME::RefreshKeysJob *refreshKeysJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::CMS) { // fixme: add support for gpg, too
-            return 0;
+            return nullptr;
         }
 
         // this operation is not supported by gpgme, so we have to call gpgsm ourselves:
@@ -265,7 +265,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setArmor(armor);
@@ -278,7 +278,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEDeleteJob(context);
     }
@@ -287,7 +287,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setArmor(armor);
@@ -299,7 +299,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
 
         context->setTextMode(textMode);
@@ -309,12 +309,12 @@ public:
     QGpgME::ChangeExpiryJob *changeExpiryJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return 0;    // only supported by gpg
+            return nullptr;    // only supported by gpg
         }
 
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEChangeExpiryJob(context);
     }
@@ -322,11 +322,11 @@ public:
     QGpgME::ChangePasswdJob *changePasswdJob() const Q_DECL_OVERRIDE
     {
         if (!GpgME::hasFeature(GpgME::PasswdFeature, 0)) {
-            return 0;
+            return nullptr;
         }
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEChangePasswdJob(context);
     }
@@ -334,12 +334,12 @@ public:
     QGpgME::SignKeyJob *signKeyJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return 0;    // only supported by gpg
+            return nullptr;    // only supported by gpg
         }
 
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMESignKeyJob(context);
     }
@@ -347,12 +347,12 @@ public:
     QGpgME::ChangeOwnerTrustJob *changeOwnerTrustJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return 0;    // only supported by gpg
+            return nullptr;    // only supported by gpg
         }
 
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEChangeOwnerTrustJob(context);
     }
@@ -360,12 +360,12 @@ public:
     QGpgME::AddUserIDJob *addUserIDJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return 0;    // only supported by gpg
+            return nullptr;    // only supported by gpg
         }
 
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return 0;
+            return nullptr;
         }
         return new QGpgME::QGpgMEAddUserIDJob(context);
     }
@@ -373,11 +373,11 @@ public:
     QGpgME::KeyListJob *locateKeysJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         context->setKeyListMode(GpgME::Extern | GpgME::Local | GpgME::Signatures | GpgME::Validate);
         return new QGpgME::QGpgMEKeyListJob(context);
@@ -387,7 +387,7 @@ public:
     {
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         return new QGpgME::QGpgMEKeyForMailboxJob(context);
     }
@@ -395,11 +395,11 @@ public:
     QGpgME::WKSPublishJob *wksPublishJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         auto context = GpgME::Context::createForEngine(GpgME::SpawnEngine);
         if (!context) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         return new QGpgME::QGpgMEWKSPublishJob(context.release());
     }
@@ -407,11 +407,11 @@ public:
     QGpgME::TofuPolicyJob *tofuPolicyJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         return new QGpgME::QGpgMETofuPolicyJob(context);
     }
@@ -419,11 +419,11 @@ public:
     QGpgME::QuickJob *quickJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::OpenPGP) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
         if (!context) {
-            return Q_NULLPTR;
+            return nullptr;
         }
         return new QGpgME::QGpgMEQuickJob(context);
     }
diff --git a/lang/qt/src/qgpgmebackend.cpp b/lang/qt/src/qgpgmebackend.cpp
index 89f7b559..f7393f09 100644
--- a/lang/qt/src/qgpgmebackend.cpp
+++ b/lang/qt/src/qgpgmebackend.cpp
@@ -52,18 +52,18 @@ const char QGpgME::QGpgMEBackend::SMIME[] = "SMIME";
 
 
 QGpgME::QGpgMEBackend::QGpgMEBackend()
-    : mCryptoConfig(0),
-      mOpenPGPProtocol(0),
-      mSMIMEProtocol(0)
+    : mCryptoConfig(nullptr),
+      mOpenPGPProtocol(nullptr),
+      mSMIMEProtocol(nullptr)
 {
     GpgME::initializeLibrary();
 }
 
 QGpgME::QGpgMEBackend::~QGpgMEBackend()
 {
-    delete mCryptoConfig; mCryptoConfig = 0;
-    delete mOpenPGPProtocol; mOpenPGPProtocol = 0;
-    delete mSMIMEProtocol; mSMIMEProtocol = 0;
+    delete mCryptoConfig; mCryptoConfig = nullptr;
+    delete mOpenPGPProtocol; mOpenPGPProtocol = nullptr;
+    delete mSMIMEProtocol; mSMIMEProtocol = nullptr;
 }
 
 QString QGpgME::QGpgMEBackend::name() const
@@ -163,7 +163,7 @@ QGpgME::Protocol *QGpgME::QGpgMEBackend::protocol(const char *name) const
     if (qstricmp(name, SMIME) == 0) {
         return smime();
     }
-    return 0;
+    return nullptr;
 }
 
 bool QGpgME::QGpgMEBackend::supportsProtocol(const char *name) const
@@ -176,7 +176,7 @@ const char *QGpgME::QGpgMEBackend::enumerateProtocols(int i) const
     switch (i) {
     case 0: return OpenPGP;
     case 1: return SMIME;
-    default: return 0;
+    default: return nullptr;
     }
 }
 
diff --git a/lang/qt/src/qgpgmedecryptjob.cpp b/lang/qt/src/qgpgmedecryptjob.cpp
index 598e22fb..c33a4b5f 100644
--- a/lang/qt/src/qgpgmedecryptjob.cpp
+++ b/lang/qt/src/qgpgmedecryptjob.cpp
@@ -100,7 +100,7 @@ static QGpgMEDecryptJob::result_type decrypt_qba(Context *ctx, const QByteArray
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return decrypt(ctx, 0, buffer, std::shared_ptr<QIODevice>());
+    return decrypt(ctx, nullptr, buffer, std::shared_ptr<QIODevice>());
 }
 
 Error QGpgMEDecryptJob::start(const QByteArray &cipherText)
diff --git a/lang/qt/src/qgpgmedecryptverifyjob.cpp b/lang/qt/src/qgpgmedecryptverifyjob.cpp
index 01cf2478..9b3f73db 100644
--- a/lang/qt/src/qgpgmedecryptverifyjob.cpp
+++ b/lang/qt/src/qgpgmedecryptverifyjob.cpp
@@ -108,7 +108,7 @@ static QGpgMEDecryptVerifyJob::result_type decrypt_verify_qba(Context *ctx, cons
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return decrypt_verify(ctx, 0, buffer, std::shared_ptr<QIODevice>());
+    return decrypt_verify(ctx, nullptr, buffer, std::shared_ptr<QIODevice>());
 }
 
 Error QGpgMEDecryptVerifyJob::start(const QByteArray &cipherText)
diff --git a/lang/qt/src/qgpgmeencryptjob.cpp b/lang/qt/src/qgpgmeencryptjob.cpp
index aacec297..8fb3dd3f 100644
--- a/lang/qt/src/qgpgmeencryptjob.cpp
+++ b/lang/qt/src/qgpgmeencryptjob.cpp
@@ -118,7 +118,7 @@ static QGpgMEEncryptJob::result_type encrypt_qba(Context *ctx, const std::vector
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return encrypt(ctx, 0, recipients, buffer, std::shared_ptr<QIODevice>(), eflags, outputIsBsse64Encoded);
+    return encrypt(ctx, nullptr, recipients, buffer, std::shared_ptr<QIODevice>(), eflags, outputIsBsse64Encoded);
 }
 
 Error QGpgMEEncryptJob::start(const std::vector<Key> &recipients, const QByteArray &plainText, bool alwaysTrust)
diff --git a/lang/qt/src/qgpgmekeylistjob.cpp b/lang/qt/src/qgpgmekeylistjob.cpp
index 891b0bd7..295e612d 100644
--- a/lang/qt/src/qgpgmekeylistjob.cpp
+++ b/lang/qt/src/qgpgmekeylistjob.cpp
@@ -69,7 +69,7 @@ static KeyListResult do_list_keys(Context *ctx, const QStringList &pats, std::ve
     const _detail::PatternConverter pc(pats);
 
     if (const Error err = ctx->startKeyListing(pc.patterns(), secretOnly)) {
-        return KeyListResult(0, err);
+        return KeyListResult(nullptr, err);
     }
 
     Error err;
diff --git a/lang/qt/src/qgpgmelistallkeysjob.cpp b/lang/qt/src/qgpgmelistallkeysjob.cpp
index 0ed32ce7..82483f25 100644
--- a/lang/qt/src/qgpgmelistallkeysjob.cpp
+++ b/lang/qt/src/qgpgmelistallkeysjob.cpp
@@ -64,9 +64,9 @@ QGpgMEListAllKeysJob::~QGpgMEListAllKeysJob() {}
 static KeyListResult do_list_keys(Context *ctx, std::vector<Key> &keys, bool secretOnly)
 {
 
-    const char **pat = 0;
+    const char **pat = nullptr;
     if (const Error err = ctx->startKeyListing(pat, secretOnly)) {
-        return KeyListResult(0, err);
+        return KeyListResult(nullptr, err);
     }
 
     Error err;
diff --git a/lang/qt/src/qgpgmerefreshkeysjob.cpp b/lang/qt/src/qgpgmerefreshkeysjob.cpp
index 1ff26ecc..ae862e04 100644
--- a/lang/qt/src/qgpgmerefreshkeysjob.cpp
+++ b/lang/qt/src/qgpgmerefreshkeysjob.cpp
@@ -53,8 +53,8 @@
 #include <assert.h>
 
 QGpgME::QGpgMERefreshKeysJob::QGpgMERefreshKeysJob()
-    : RefreshKeysJob(0),
-      mProcess(0),
+    : RefreshKeysJob(nullptr),
+      mProcess(nullptr),
       mError(0)
 {
 
@@ -142,7 +142,7 @@ void QGpgME::QGpgMERefreshKeysJob::slotCancel()
     if (mProcess) {
         mProcess->kill();
     }
-    mProcess = 0;
+    mProcess = nullptr;
     mError = GpgME::Error::fromCode(GPG_ERR_CANCELED, GPG_ERR_SOURCE_GPGSM);
 }
 
diff --git a/lang/qt/src/qgpgmesecretkeyexportjob.cpp b/lang/qt/src/qgpgmesecretkeyexportjob.cpp
index 0a410179..d77a50ab 100644
--- a/lang/qt/src/qgpgmesecretkeyexportjob.cpp
+++ b/lang/qt/src/qgpgmesecretkeyexportjob.cpp
@@ -52,8 +52,8 @@
 #include <assert.h>
 
 QGpgME::QGpgMESecretKeyExportJob::QGpgMESecretKeyExportJob(bool armour, const QString &charset)
-    : ExportJob(0),
-      mProcess(0),
+    : ExportJob(nullptr),
+      mProcess(nullptr),
       mError(0),
       mArmour(armour),
       mCharset(charset)
@@ -114,7 +114,7 @@ void QGpgME::QGpgMESecretKeyExportJob::slotCancel()
     if (mProcess) {
         mProcess->kill();
     }
-    mProcess = 0;
+    mProcess = nullptr;
     mError = GpgME::Error::fromCode(GPG_ERR_CANCELED, GPG_ERR_SOURCE_GPGSM);
 }
 
diff --git a/lang/qt/src/qgpgmesignencryptjob.cpp b/lang/qt/src/qgpgmesignencryptjob.cpp
index bfaf58c9..284c1106 100644
--- a/lang/qt/src/qgpgmesignencryptjob.cpp
+++ b/lang/qt/src/qgpgmesignencryptjob.cpp
@@ -123,7 +123,7 @@ static QGpgMESignEncryptJob::result_type sign_encrypt_qba(Context *ctx, const st
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return sign_encrypt(ctx, 0, signers, recipients, buffer, std::shared_ptr<QIODevice>(), eflags, outputIsBsse64Encoded);
+    return sign_encrypt(ctx, nullptr, signers, recipients, buffer, std::shared_ptr<QIODevice>(), eflags, outputIsBsse64Encoded);
 }
 
 Error QGpgMESignEncryptJob::start(const std::vector<Key> &signers, const std::vector<Key> &recipients, const QByteArray &plainText, bool alwaysTrust)
diff --git a/lang/qt/src/qgpgmesignjob.cpp b/lang/qt/src/qgpgmesignjob.cpp
index 7e710f39..e89b9457 100644
--- a/lang/qt/src/qgpgmesignjob.cpp
+++ b/lang/qt/src/qgpgmesignjob.cpp
@@ -129,7 +129,7 @@ static QGpgMESignJob::result_type sign_qba(Context *ctx,
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return sign(ctx, 0, signers, buffer, std::shared_ptr<QIODevice>(), mode, outputIsBsse64Encoded);
+    return sign(ctx, nullptr, signers, buffer, std::shared_ptr<QIODevice>(), mode, outputIsBsse64Encoded);
 }
 
 Error QGpgMESignJob::start(const std::vector<Key> &signers, const QByteArray &plainText, SignatureMode mode)
diff --git a/lang/qt/src/qgpgmeverifyopaquejob.cpp b/lang/qt/src/qgpgmeverifyopaquejob.cpp
index bd7636dc..56c0f50e 100644
--- a/lang/qt/src/qgpgmeverifyopaquejob.cpp
+++ b/lang/qt/src/qgpgmeverifyopaquejob.cpp
@@ -99,7 +99,7 @@ static QGpgMEVerifyOpaqueJob::result_type verify_opaque_qba(Context *ctx, const
     if (!buffer->open(QIODevice::ReadOnly)) {
         assert(!"This should never happen: QBuffer::open() failed");
     }
-    return verify_opaque(ctx, 0, buffer, std::shared_ptr<QIODevice>());
+    return verify_opaque(ctx, nullptr, buffer, std::shared_ptr<QIODevice>());
 }
 
 Error QGpgMEVerifyOpaqueJob::start(const QByteArray &signedData)
diff --git a/lang/qt/src/threadedjobmixin.cpp b/lang/qt/src/threadedjobmixin.cpp
index cd7c494f..d5399f7b 100644
--- a/lang/qt/src/threadedjobmixin.cpp
+++ b/lang/qt/src/threadedjobmixin.cpp
@@ -164,13 +164,13 @@ static QList<QByteArray> single(const QByteArray &ba)
 }
 
 _detail::PatternConverter::PatternConverter(const QByteArray &ba)
-    : m_list(single(ba)), m_patterns(0) {}
+    : m_list(single(ba)), m_patterns(nullptr) {}
 _detail::PatternConverter::PatternConverter(const QString &s)
-    : m_list(single(s.toUtf8())), m_patterns(0) {}
+    : m_list(single(s.toUtf8())), m_patterns(nullptr) {}
 _detail::PatternConverter::PatternConverter(const QList<QByteArray> &lba)
-    : m_list(lba), m_patterns(0) {}
+    : m_list(lba), m_patterns(nullptr) {}
 _detail::PatternConverter::PatternConverter(const QStringList &sl)
-    :  m_list(from_sl(sl)), m_patterns(0) {}
+    :  m_list(from_sl(sl)), m_patterns(nullptr) {}
 
 const char **_detail::PatternConverter::patterns() const
 {
@@ -178,7 +178,7 @@ const char **_detail::PatternConverter::patterns() const
         m_patterns = new const char *[ m_list.size() + 1 ];
         const char **end = std::transform(m_list.begin(), m_list.end(), m_patterns,
                                           std::mem_fn(&QByteArray::constData));
-        *end = 0;
+        *end = nullptr;
     }
     return m_patterns;
 }
diff --git a/lang/qt/src/threadedjobmixin.h b/lang/qt/src/threadedjobmixin.h
index 32cdb8e6..ef30ab36 100644
--- a/lang/qt/src/threadedjobmixin.h
+++ b/lang/qt/src/threadedjobmixin.h
@@ -148,7 +148,7 @@ protected:
                   "Last result type not a GpgME::Error");
 
     explicit ThreadedJobMixin(GpgME::Context *ctx)
-        : T_base(0), m_ctx(ctx), m_thread(), m_auditLog(), m_auditLogError()
+        : T_base(nullptr), m_ctx(ctx), m_thread(), m_auditLog(), m_auditLogError()
     {
     }