[PATCH] lib: work around talloc_steal usage from C++ code

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+From: Jani Nikula <jani@nikula.org>\r
+To: notmuch@notmuchmail.org\r
+Subject: [PATCH] lib: work around talloc_steal usage from C++ code\r
+Date: Thu, 12 Apr 2012 23:57:39 +0300\r
+Message-Id: <1334264259-17632-1-git-send-email-jani@nikula.org>\r
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+\r
+Implicit typecast from 'void *' to 'T *' is okay in C, but not in\r
+C++. In talloc_steal, an explicit cast is provided for type safety in\r
+some GCC versions. Otherwise, a cast is required. Provide a template\r
+function for this to maintain type safety, and redefine talloc_steal\r
+to use it.\r
+\r
+The template must be outside the extern "C" block (NOTMUCH_BEGIN_DECLS\r
+and NOTMUCH_END_DECLS), but keep it within the GCC visibility #pragma.\r
+\r
+No functional changes, apart from making the library build with\r
+compilers other than recent GCC.\r
+\r
+Signed-off-by: Jani Nikula <jani@nikula.org>\r
+\r
+---\r
+\r
+For background, see discussion starting at\r
+id:"1333966665-10469-5-git-send-email-Vladimir.Marek@oracle.com"\r
+\r
+Vladimir, please test this. Thanks.\r
+---\r
+ lib/notmuch-private.h |   22 ++++++++++++++++++++--\r
+ 1 files changed, 20 insertions(+), 2 deletions(-)\r
+\r
+diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h\r
+index ea836f7..3886e0c 100644\r
+--- a/lib/notmuch-private.h\r
++++ b/lib/notmuch-private.h\r
+@@ -495,8 +495,26 @@ notmuch_filenames_t *\r
+ _notmuch_filenames_create (const void *ctx,\r
+                          notmuch_string_list_t *list);\r
+ \r
+-#pragma GCC visibility pop\r
+-\r
+ NOTMUCH_END_DECLS\r
+ \r
++#ifdef __cplusplus\r
++/* Implicit typecast from 'void *' to 'T *' is okay in C, but not in\r
++ * C++. In talloc_steal, an explicit cast is provided for type safety\r
++ * in some GCC versions. Otherwise, a cast is required. Provide a\r
++ * template function for this to maintain type safety, and redefine\r
++ * talloc_steal to use it.\r
++ */\r
++#if !(__GNUC__ >= 3)\r
++template <class T> T *\r
++_notmuch_talloc_steal (const void *new_ctx, const T *ptr)\r
++{\r
++    return static_cast<T *> (talloc_steal (new_ctx, ptr));\r
++}\r
++#undef talloc_steal\r
++#define talloc_steal _notmuch_talloc_steal\r
++#endif\r
++#endif\r
++\r
++#pragma GCC visibility pop\r
++\r
+ #endif\r
+-- \r
+1.7.5.4\r
+\r