Add attribute(warn_unused_result)

This adds a compiler check that the function result is used by the caller and enables it by default for all cairo_private functions and for public API that returns a cairo_status_t. It has been discussed that to extend the warnings to all functions, a new function type could been introduced to cover static functions: cairo_static. This has not been done at the present time in order to minimise the churn and focus on the more common errors. In order to reduce the warning spew generated by gcc for invalid use of this attribute, -Wno-attributes is added to CFLAGS. This has the unfortunate side-effect of masking future warnings for all attributes - be warned!
2026-05-08 19:38:02 +02:00 · 2007-04-08 20:50:08 +01:00 · 2007-04-08 20:50:08 +01:00 · 46eab95698
commit 46eab95698
parent 9da86e4a38
6 changed files with 41 additions and 27 deletions
--- a/configure.in
+++ b/configure.in
@ -623,7 +623,8 @@ MAYBE_WARN="-Wall -Wextra \
 -Wpacked -Wswitch-enum -Wmissing-format-attribute \
 -Wstrict-aliasing=2 -Winit-self -Wunsafe-loop-optimizations \
 -Wdeclaration-after-statement -Wold-style-definition \
-Wno-missing-field-initializers -Wno-unused-parameter"
+-Wno-missing-field-initializers -Wno-unused-parameter \
+-Wno-attributes"


 # invalidate cached value if MAYBE_WARN has changed
@ -844,9 +845,19 @@ AC_CONFIG_COMMANDS([src/cairo-features.h],
 # define CAIRO_END_DECLS
 #endif

+#if    __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+#define CAIRO_WARN_UNUSED_RESULT 		\
+  __attribute__((__warn_unused_result__))
+#else
+#define CAIRO_WARN_UNUSED_RESULT
+#endif /* __GNUC__ */
+
 #ifndef cairo_public
 # define cairo_public
 #endif
+#ifndef cairo_public_warn
+# define cairo_public_warn CAIRO_WARN_UNUSED_RESULT
+#endif

 #define CAIRO_VERSION_MAJOR $CAIRO_VERSION_MAJOR
 #define CAIRO_VERSION_MINOR $CAIRO_VERSION_MINOR
--- a/pixman/configure.in
+++ b/pixman/configure.in
@ -45,7 +45,8 @@ WARN_CFLAGS=""
 if test "x$GCC" = "xyes"; then
 	WARN_CFLAGS="-Wall -Wpointer-arith -Wstrict-prototypes \
 	-Wmissing-prototypes -Wmissing-declarations \
-	-Wnested-externs -fno-strict-aliasing"
+	-Wnested-externs -fno-strict-aliasing \
+	-Wno-attributes"
 fi

 AC_SUBST(WARN_CFLAGS)
--- a/pixman/src/pixman.h
+++ b/pixman/src/pixman.h
@ -100,7 +100,7 @@ SOFTWARE.
 #include "pixman-remap.h"

 #if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3)) && defined(__ELF__) && !defined(__sun__)
-#define pixman_private		__attribute__((__visibility__("hidden")))
+#define pixman_private		__attribute__((__visibility__("hidden"),__warn_unused_result__))
 #elif defined(__SUNPRO_C) && (__SUNPRO_C >= 0x550)
 #define pixman_private		__hidden
 #else /* not gcc >= 3.3 and not Sun Studio >= 8 */
--- a/src/cairo.h
+++ b/src/cairo.h
@ -313,7 +313,7 @@ cairo_public void *
 cairo_get_user_data (cairo_t			 *cr,
 		     const cairo_user_data_key_t *key);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_set_user_data (cairo_t			 *cr,
 		     const cairo_user_data_key_t *key,
 		     void			 *user_data,
@ -972,7 +972,7 @@ cairo_font_options_copy (const cairo_font_options_t *original);
 cairo_public void
 cairo_font_options_destroy (cairo_font_options_t *options);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_font_options_status (cairo_font_options_t *options);

 cairo_public void
@ -1088,7 +1088,7 @@ cairo_font_face_destroy (cairo_font_face_t *font_face);
 cairo_public unsigned int
 cairo_font_face_get_reference_count (cairo_font_face_t *font_face);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_font_face_status (cairo_font_face_t *font_face);

 /**
@ -1141,7 +1141,7 @@ cairo_public void *
 cairo_font_face_get_user_data (cairo_font_face_t	   *font_face,
 			       const cairo_user_data_key_t *key);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_font_face_set_user_data (cairo_font_face_t	   *font_face,
 			       const cairo_user_data_key_t *key,
 			       void			   *user_data,
@ -1164,7 +1164,7 @@ cairo_scaled_font_destroy (cairo_scaled_font_t *scaled_font);
 cairo_public unsigned int
 cairo_scaled_font_get_reference_count (cairo_scaled_font_t *scaled_font);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_scaled_font_status (cairo_scaled_font_t *scaled_font);

 cairo_public cairo_font_type_t
@ -1174,7 +1174,7 @@ cairo_public void *
 cairo_scaled_font_get_user_data (cairo_scaled_font_t         *scaled_font,
 				 const cairo_user_data_key_t *key);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_scaled_font_set_user_data (cairo_scaled_font_t         *scaled_font,
 				 const cairo_user_data_key_t *key,
 				 void                        *user_data,
@ -1392,7 +1392,7 @@ cairo_path_destroy (cairo_path_t *path);

 /* Error status queries */

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_status (cairo_t *cr);

 cairo_public const char *
@ -1418,7 +1418,7 @@ cairo_surface_destroy (cairo_surface_t *surface);
 cairo_public unsigned int
 cairo_surface_get_reference_count (cairo_surface_t *surface);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_surface_status (cairo_surface_t *surface);

 /**
@ -1482,11 +1482,11 @@ cairo_surface_get_content (cairo_surface_t *surface);

 #if CAIRO_HAS_PNG_FUNCTIONS

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_surface_write_to_png (cairo_surface_t	*surface,
 			    const char		*filename);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_surface_write_to_png_stream (cairo_surface_t	*surface,
 				   cairo_write_func_t	write_func,
 				   void			*closure);
@ -1497,7 +1497,7 @@ cairo_public void *
 cairo_surface_get_user_data (cairo_surface_t		 *surface,
 			     const cairo_user_data_key_t *key);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_surface_set_user_data (cairo_surface_t		 *surface,
 			     const cairo_user_data_key_t *key,
 			     void			 *user_data,
@ -1642,14 +1642,14 @@ cairo_pattern_destroy (cairo_pattern_t *pattern);
 cairo_public unsigned int
 cairo_pattern_get_reference_count (cairo_pattern_t *pattern);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_status (cairo_pattern_t *pattern);

 cairo_public void *
 cairo_pattern_get_user_data (cairo_pattern_t		 *pattern,
 			     const cairo_user_data_key_t *key);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_set_user_data (cairo_pattern_t		 *pattern,
 			     const cairo_user_data_key_t *key,
 			     void			 *user_data,
@ -1758,32 +1758,32 @@ cairo_pattern_set_filter (cairo_pattern_t *pattern, cairo_filter_t filter);
 cairo_public cairo_filter_t
 cairo_pattern_get_filter (cairo_pattern_t *pattern);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_rgba (cairo_pattern_t *pattern,
 			double *red, double *green,
 			double *blue, double *alpha);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_surface (cairo_pattern_t *pattern,
 			   cairo_surface_t **surface);


-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_color_stop_rgba (cairo_pattern_t *pattern,
 				   int index, double *offset,
 				   double *red, double *green,
 				   double *blue, double *alpha);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_color_stop_count (cairo_pattern_t *pattern,
 				    int *count);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_linear_points (cairo_pattern_t *pattern,
 				 double *x0, double *y0,
 				 double *x1, double *y1);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_pattern_get_radial_circles (cairo_pattern_t *pattern,
 				  double *x0, double *y0, double *r0,
 				  double *x1, double *y1, double *r1);
@ -1820,7 +1820,7 @@ cairo_matrix_scale (cairo_matrix_t *matrix, double sx, double sy);
 cairo_public void
 cairo_matrix_rotate (cairo_matrix_t *matrix, double radians);

-cairo_public cairo_status_t
+cairo_public_warn cairo_status_t
 cairo_matrix_invert (cairo_matrix_t *matrix);

 cairo_public void
--- a/src/cairoint.h
+++ b/src/cairoint.h
@ -102,13 +102,15 @@ CAIRO_BEGIN_DECLS

 /* slim_internal.h */
 #if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3)) && defined(__ELF__) && !defined(__sun)
-#define cairo_private		__attribute__((__visibility__("hidden")))
+#define cairo_private			__attribute__((__visibility__("hidden"),__warn_unused_result__))
 #elif defined(__SUNPRO_C) && (__SUNPRO_C >= 0x550)
-#define cairo_private		__hidden
+#define cairo_private			__hidden CAIRO_WARN_UNUSED_RESULT
 #else /* not gcc >= 3.3 and not Sun Studio >= 8 */
-#define cairo_private
+#define cairo_private			CAIRO_WARN_UNUSED_RESULT
 #endif

+#define cairo_warn CAIRO_WARN_UNUSED_RESULT
+
 /* This macro allow us to deprecate a function by providing an alias
   for the old function name to the new function name. With this
   macro, binary compatibility is preserved. The macro only works on
--- a/src/check-headers.sh
+++ b/src/check-headers.sh
@ -12,7 +12,7 @@ xargs grep -B 1 '^cairo_.*[ 	]\+(' |
 awk '
 /^--$/ { context=""; public=0; next; }
 /:cairo_.*[ 	]+\(/ { if (!public) {print context; print; print "--";} next; }
-/-cairo_public[ 	]/ {public=1;}
+/-cairo_public.*[ 	]/ {public=1;}
 { context=$0; }
 ' |
 sed 's/[.]h-/.h:/' |