Add configure check for nonnull attribute

The main reason I do this is to document the minimum compiler version
(GCC 3.3) for the attribute. But it may work with other compilers, too.

Signed-off-by: Kang-Che Sung <[email protected]>

Macros.h

@@ -42,21 +42,31 @@ in the source distribution for its full text.
 #ifdef __GNUC__ // defined by GCC and Clang
 
 #define ATTR_FORMAT(type, index, check) __attribute__((format (type, index, check)))
-#define ATTR_NONNULL __attribute__((nonnull))
 #define ATTR_NORETURN __attribute__((noreturn))
 #define ATTR_UNUSED __attribute__((unused))
 #define ATTR_MALLOC __attribute__((malloc))
 
 #else /* __GNUC__ */
 
 #define ATTR_FORMAT(type, index, check)
-#define ATTR_NONNULL
 #define ATTR_NORETURN
 #define ATTR_UNUSED
 #define ATTR_MALLOC
 
 #endif /* __GNUC__ */
 
+#ifdef HAVE_ATTR_NONNULL
+
+#define ATTR_NONNULL __attribute__((nonnull))
+#define ATTR_NONNULL_N(...) __attribute__((nonnull(__VA_ARGS__)))
+
+#else
+
+#define ATTR_NONNULL
+#define ATTR_NONNULL_N(...)
+
+#endif /* HAVE_ATTR_NONNULL */
+
 #ifdef HAVE_ATTR_ALLOC_SIZE
 
 #define ATTR_ALLOC_SIZE1(a) __attribute__((alloc_size (a)))

configure.ac

@@ -202,6 +202,22 @@ AC_COMPILE_IFELSE([
  AC_MSG_RESULT(no))
 CFLAGS="$old_CFLAGS"
 
+AC_MSG_CHECKING(for nonnull)
+old_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -Wno-error -Werror=attributes"
+AC_COMPILE_IFELSE([
+ AC_LANG_SOURCE(
+ [[
+ /* Attribute supported in GCC 3.3 or later */
+ __attribute__((nonnull)) int my_strcmp(const char* a, const char* b);
+ __attribute__((nonnull(1))) long my_strtol(const char* str, char** endptr, int base);
+ ]]
+ )],
+ AC_DEFINE([HAVE_ATTR_NONNULL], 1, [The nonnull attribute is supported.])
+ AC_MSG_RESULT(yes),
+ AC_MSG_RESULT(no))
+CFLAGS="$old_CFLAGS"
+
 AC_MSG_CHECKING(for NaN support)
 dnl Note: AC_RUN_IFELSE does not try compiling the program at all when
 dnl $cross_compiling is 'yes'.