Let GCC check format arguments

Author: Sascha Schumann

main/php.h

@@ -226,6 +226,12 @@ char *strerror(int);
 #define LONG_MIN (- LONG_MAX - 1)
 #endif
 
+#ifdef __GNUC__
+# define PHP_ATTRIBUTE_FORMAT(type, idx, first) __attribute__ ((format(type, idx, first)))
+#else
+# define PHP_ATTRIBUTE_FORMAT(type, idx, first)
+#endif
+
 #if !defined(HAVE_SNPRINTF) || !defined(HAVE_VSNPRINTF) || PHP_BROKEN_SPRINTF || PHP_BROKEN_SNPRINTF || PHP_BROKEN_VSNPRINTF
 #include "snprintf.h"
 #endif

main/snprintf.h

@@ -65,17 +65,17 @@ spprintf is the dynamical version of snprintf. It allocates the buffer in size
 #define SNPRINTF_H
 
 #if !defined(HAVE_SNPRINTF) || PHP_BROKEN_SNPRINTF
-extern int ap_php_snprintf(char *, size_t, const char *, ...);
+int ap_php_snprintf(char *, size_t, const char *, ...) PHP_ATTRIBUTE_FORMAT(printf, 3, 4);
 #define snprintf ap_php_snprintf
 #endif
 
 #if !defined(HAVE_VSNPRINTF) || PHP_BROKEN_VSNPRINTF
-extern int ap_php_vsnprintf(char *, size_t, const char *, va_list ap);
+int ap_php_vsnprintf(char *, size_t, const char *, va_list ap) PHP_ATTRIBUTE_FORMAT(printf, 3, 0);
 #define vsnprintf ap_php_vsnprintf
 #endif
 
 #if PHP_BROKEN_SPRINTF
-int php_sprintf (char* s, const char* format, ...);
+int php_sprintf (char* s, const char* format, ...) PHP_ATTRIBUTE_FORMAT(printf, 2, 3);
 #define sprintf php_sprintf
 #endif
 

main/spprintf.h

@@ -37,9 +37,9 @@ There is also snprintf: See difference explained in snprintf.h
 #include "snprintf.h"
 
 BEGIN_EXTERN_C()
-PHPAPI extern int spprintf( char **pbuf, size_t max_len, const char *format, ...);
+PHPAPI int spprintf( char **pbuf, size_t max_len, const char *format, ...) PHP_ATTRIBUTE_FORMAT(printf, 3, 4);
 
-PHPAPI extern int vspprintf(char **pbuf, size_t max_len, const char *format, va_list ap);
+PHPAPI int vspprintf(char **pbuf, size_t max_len, const char *format, va_list ap) PHP_ATTRIBUTE_FORMAT(printf, 3, 0);
 END_EXTERN_C()
 
 #endif /* SNPRINTF_H */