Enable "unused result" warning for Visual Studio >= 2012 (MSVC 11.0)

The _Must_inspect_result_ annotation is documented to be used in both
the declaration and implementation, but in testing with the MSVC 2012
compiler it appears to be sufficient to use the annotation only in the
declaration to get a compiler warning, as with the GCC compiler.
So the annotation is not necessary in the C implementation.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=105460
[smcv: Rebase dbus-sysdeps.h changes on master]
[smcv: Clarify commit message]
Reviewed-by: Simon McVittie <smcv@collabora.com>
Tested-by: Daniel Wendt <daniel.wendt@linux.com>

7 files changed, 45 insertions, 22 deletions

diff --git a/README.cmake b/README.cmake
index 6d5621fd..2fe33dcd 100644
--- a/README.cmake
+++ b/README.cmake
@@ -165,6 +165,10 @@ x11 only:
 // Build with X11 auto launch support
 DBUS_BUILD_X11:BOOL=ON
 
+MSVC only (Visual Studio >= 2012):
+// Enable code analyzing for MSVC compiler: /analyze
+DBUS_MSVC_ANALYZE:BOOL=OFF
+
 
 Note: The above mentioned options could be extracted after 
 configuring from the output of running "<maketool> help-options" 
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 3becfc90..c1f0f165 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -170,6 +170,7 @@ if(MSVC)
     ADD_DEFINITIONS(-D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE)
     SET(CMAKE_C_FLAGS_DEBUG   "${CMAKE_C_FLAGS_DEBUG}   /FIconfig.h")
     SET(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} /FIconfig.h")
+    option (DBUS_MSVC_ANALYZE "Enable code analyzing for MSVC compiler: /analyze" OFF)
 endif()
 
 #
@@ -212,6 +213,9 @@ if(MSVC)
     # 4114 same type qualifier used more than once
     # 4133 'type' : incompatible types - from 'type1' to 'type2'
     set(WARNINGS_ERRORS "4002 4003 4013 4028 4031 4047 4114 4133")
+    if(DBUS_MSVC_ANALYZE AND MSVC_VERSION GREATER 1600)
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /analyze")
+    endif()
 else()
     set(WARNINGS "sign-compare")
     set(WARNINGS_DISABLED "")
@@ -588,6 +592,9 @@ message("        Docbook Generator:        ${DOCBOOK_GENERATOR_NAME}           "
 
 
 message("        gcc coverage profiling:   ${DBUS_GCOV_ENABLED}                ")
+if(MSVC)
+message("        MSVC code analyze mode:   ${DBUS_MSVC_ANALYZE}                ")
+endif()
 message("        Building unit tests:      ${DBUS_BUILD_TESTS}                 ")
 message("        Building with GLib:       ${DBUS_WITH_GLIB}                   ")
 message("        Building verbose mode:    ${DBUS_ENABLE_VERBOSE_MODE}         ")
diff --git a/dbus/dbus-internals.h b/dbus/dbus-internals.h
index 57a67d08..ae9ab626 100644
--- a/dbus/dbus-internals.h
+++ b/dbus/dbus-internals.h
@@ -366,7 +366,8 @@ typedef enum
   _DBUS_N_GLOBAL_LOCKS
 } DBusGlobalLock;
 
-dbus_bool_t _dbus_lock   (DBusGlobalLock lock) _DBUS_GNUC_WARN_UNUSED_RESULT;
+_DBUS_WARN_UNUSED_RESULT
+dbus_bool_t _dbus_lock   (DBusGlobalLock lock);
 void        _dbus_unlock (DBusGlobalLock lock);
 
 #define _DBUS_LOCK_NAME(name)           _DBUS_LOCK_##name
@@ -399,7 +400,7 @@ union DBusGUID
   char as_bytes[DBUS_UUID_LENGTH_BYTES];                /**< guid as 16 single-byte values */
 };
 
-DBUS_PRIVATE_EXPORT _DBUS_GNUC_WARN_UNUSED_RESULT
+DBUS_PRIVATE_EXPORT _DBUS_WARN_UNUSED_RESULT
 dbus_bool_t _dbus_generate_uuid  (DBusGUID         *uuid,
                                   DBusError        *error);
 DBUS_PRIVATE_EXPORT
diff --git a/dbus/dbus-macros.h b/dbus/dbus-macros.h
index 2c8956e3..bf3a0b0d 100644
--- a/dbus/dbus-macros.h
+++ b/dbus/dbus-macros.h
@@ -92,10 +92,24 @@
 #define DBUS_ALLOC_SIZE2(x,y)
 #endif
 
-#if    (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
-#define _DBUS_GNUC_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+/** @def _DBUS_WARN_UNUSED_RESULT
+ *
+ * An attribute for functions whose result must be checked by the caller.
+ *
+ * This macro is used in function declarations. Unlike gcc-specific
+ * attributes, to avoid compilation failure with MSVC it must appear
+ * somewhere before the function name in the declaration. Our preferred
+ * coding style is to place it before the return type, for example:
+ *
+ * DBUS_PRIVATE_EXPORT _DBUS_WARN_UNUSED_RESULT
+ * dbus_bool_t _dbus_user_database_lock_system (void);
+ */
+#if     defined(_MSC_VER) && (_MSC_VER >= 1700)
+#define _DBUS_WARN_UNUSED_RESULT _Must_inspect_result_
+#elif    (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+#define _DBUS_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 #else
-#define _DBUS_GNUC_WARN_UNUSED_RESULT
+#define _DBUS_WARN_UNUSED_RESULT
 #endif
 
 /** @def _DBUS_GNUC_PRINTF
@@ -104,9 +118,6 @@
 /** @def _DBUS_GNUC_NORETURN
  * used to tell gcc about functions that never return, such as _dbus_abort()
  */
-/** @def _DBUS_GNUC_WARN_UNUSED_RESULT
- * used to tell gcc about functions whose result must be used
- */
 
 /* Normally docs are in .c files, but there isn't a .c file for this. */
 /**
diff --git a/dbus/dbus-sysdeps.h b/dbus/dbus-sysdeps.h
index 171af7b5..8961c33f 100644
--- a/dbus/dbus-sysdeps.h
+++ b/dbus/dbus-sysdeps.h
@@ -132,18 +132,18 @@ typedef struct { SOCKET sock; } DBusSocket;
 # define DBUS_SOCKET_FORMAT "Iu"
 # define DBUS_SOCKET_INIT { INVALID_SOCKET }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline SOCKET
 _dbus_socket_printable (DBusSocket s) { return s.sock; }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline dbus_bool_t
 _dbus_socket_is_valid (DBusSocket s) { return s.sock != INVALID_SOCKET; }
 
 static inline void
 _dbus_socket_invalidate (DBusSocket *s) { s->sock = INVALID_SOCKET; }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline int
 _dbus_socket_get_int (DBusSocket s) { return (int)s.sock; }
 
@@ -153,24 +153,24 @@ typedef struct { int fd; } DBusSocket;
 # define DBUS_SOCKET_FORMAT "d"
 # define DBUS_SOCKET_INIT { -1 }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline int
 _dbus_socket_printable (DBusSocket s) { return s.fd; }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline dbus_bool_t
 _dbus_socket_is_valid (DBusSocket s) { return s.fd >= 0; }
 
 static inline void
 _dbus_socket_invalidate (DBusSocket *s) { s->fd = -1; }
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline int
 _dbus_socket_get_int (DBusSocket s) { return s.fd; }
 
 #endif /* not DBUS_WIN */
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 static inline DBusSocket
 _dbus_socket_get_invalid (void)
 {
@@ -469,7 +469,7 @@ const char* _dbus_get_tmpdir      (void);
 /**
  * Random numbers 
  */
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 dbus_bool_t _dbus_generate_random_bytes_buffer (char       *buffer,
                                                 int         n_bytes,
                                                 DBusError  *error);
diff --git a/dbus/dbus-userdb.h b/dbus/dbus-userdb.h
index 53fc90b5..ac1497db 100644
--- a/dbus/dbus-userdb.h
+++ b/dbus/dbus-userdb.h
@@ -93,8 +93,8 @@ void           _dbus_group_info_free_allocated  (DBusGroupInfo    *info);
 
 DBUS_PRIVATE_EXPORT
 DBusUserDatabase* _dbus_user_database_get_system    (void);
-DBUS_PRIVATE_EXPORT
-dbus_bool_t       _dbus_user_database_lock_system   (void) _DBUS_GNUC_WARN_UNUSED_RESULT;
+DBUS_PRIVATE_EXPORT _DBUS_WARN_UNUSED_RESULT
+dbus_bool_t       _dbus_user_database_lock_system   (void);
 DBUS_PRIVATE_EXPORT
 void              _dbus_user_database_unlock_system (void);
 void              _dbus_user_database_flush_system  (void);
diff --git a/test/test-utils.h b/test/test-utils.h
index 860ee216..14ea365d 100644
--- a/test/test-utils.h
+++ b/test/test-utils.h
@@ -10,16 +10,16 @@
 #include <dbus/dbus-internals.h>
 typedef DBusLoop TestMainContext;
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 TestMainContext *test_main_context_get            (void);
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 TestMainContext *test_main_context_try_get        (void);
 TestMainContext *test_main_context_ref            (TestMainContext *ctx);
 void             test_main_context_unref          (TestMainContext *ctx);
 void             test_main_context_iterate        (TestMainContext *ctx,
                                                    dbus_bool_t      may_block);
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 dbus_bool_t test_connection_try_setup             (TestMainContext *ctx,
                                                    DBusConnection *connection);
 void        test_connection_setup                 (TestMainContext *ctx,
@@ -27,7 +27,7 @@ void        test_connection_setup                 (TestMainContext *ctx,
 void        test_connection_shutdown              (TestMainContext *ctx,
                                                    DBusConnection *connection);
 
-_DBUS_GNUC_WARN_UNUSED_RESULT
+_DBUS_WARN_UNUSED_RESULT
 dbus_bool_t test_server_try_setup                 (TestMainContext *ctx,
                                                    DBusServer    *server);
 void        test_server_setup                     (TestMainContext *ctx,