w32: Add new global flag "w32-inst-dir".

* src/gpgme.c (gpgme_set_global_flag): Add flag "w32-inst-dir";
* src/posix-util.c (_gpgme_set_override_inst_dir): New stub.
* src/w32-util.c (override_inst_dir): New var.
(_gpgme_get_inst_dir): Return this var is set.
(_gpgme_set_override_inst_dir): New.
--

See
https://lists.gnupg.org/pipermail/gnupg-devel/2015-September/030267.html
for background.

Signed-off-by: Werner Koch <wk@gnupg.org>

doc/gpgme.texi

@@ -701,6 +701,16 @@ directory part is used as the default installation directory; the
 @code{.exe} suffix is added by GPGME.  Use forward slashed even under
 Windows.
 
+@item "w32-inst-dir"
+On Windows GPGME needs to know its installation directory to find its
+spawn helper.  This is in general no problem because a DLL has this
+information.  Some applications however link statically to GPGME and
+thus GPGME can only figure out the installation directory of this
+application which may be wrong in certain cases.  By supplying an
+installation directory as value to this flag, GPGME will assume that
+that directory is the installation directory.  This flag has no effect
+on non-Windows platforms.
+
 @end table
 
 This function returns @code{0} on success.  In contrast to other

src/gpgme.c

@@ -75,6 +75,8 @@ gpgme_set_global_flag (const char *name, const char *value)
     return _gpgme_set_default_gpgconf_name (value);
   else if (!strcmp (name, "gpg-name"))
     return _gpgme_set_default_gpg_name (value);
+  else if (!strcmp (name, "w32-inst-dir"))
+    return _gpgme_set_override_inst_dir (value);
   else
     return -1;
 }

src/posix-util.c

@@ -71,6 +71,15 @@ _gpgme_set_default_gpgconf_name (const char *name)
 }
 
 
+/* Dummy function - see w32-util.c for the actual code.  */
+int
+_gpgme_set_override_inst_dir (const char *dir)
+{
+  (void)dir;
+  return 0;
+}
+
+
 /* Find an executable program PGM along the envvar PATH.  */
 static char *
 walk_path (const char *pgm)

src/sys-util.h

@@ -23,6 +23,7 @@
 /*-- {posix,w32}-util.c --*/
 int _gpgme_set_default_gpg_name (const char *name);
 int _gpgme_set_default_gpgconf_name (const char *name);
+int _gpgme_set_override_inst_dir (const char *dir);
 
 char *_gpgme_get_gpg_path (void);
 char *_gpgme_get_gpgconf_path (void);

src/w32-util.c

@@ -85,7 +85,10 @@ static HMODULE my_hmodule;
    binaries.  The are set only once by gpgme_set_global_flag.  */
 static char *default_gpg_name;
 static char *default_gpgconf_name;
-
+/* If this variable is not NULL the value is assumed to be the
+   installation directory.  The variable may only be set once by
+   gpgme_set_global_flag and accessed by _gpgme_get_inst_dir.  */
+static char *override_inst_dir;
 
 #ifdef HAVE_ALLOW_SET_FOREGROUND_WINDOW
 
@@ -347,6 +350,9 @@ _gpgme_get_inst_dir (void)
 {
   static char *inst_dir;
 
+  if (override_inst_dir)
+    return override_inst_dir;
+
   LOCK (get_path_lock);
   if (!inst_dir)
     {
@@ -456,6 +462,28 @@ _gpgme_set_default_gpgconf_name (const char *name)
 }
 
 
+/* Set the override installation directory.  This function may only be
+   called by gpgme_set_global_flag.  Returns 0 on success.  */
+int
+_gpgme_set_override_inst_dir (const char *dir)
+{
+  if (!override_inst_dir)
+    {
+      override_inst_dir = malloc (strlen (dir) + 1);
+      if (override_inst_dir)
+        {
+          strcpy (override_inst_dir, dir);
+          replace_slashes (override_inst_dir);
+          /* Remove a trailing slash.  */
+          if (*override_inst_dir
+              && override_inst_dir[strlen (override_inst_dir)-1] == '\\')
+            override_inst_dir[strlen (override_inst_dir)-1] = 0;
+        }
+    }
+  return !override_inst_dir;
+}
+
+
 /* Return the full file name of the GPG binary.  This function is used
    iff gpgconf was not found and thus it can be assumed that gpg2 is
    not installed.  This function is only called by get_gpgconf_item