Detect PG_PRINTF_ATTRIBUTE automatically.

This eliminates gobs of "unrecognized format function type" warnings
under MinGW compilers predating GCC 4.4.

config/c-compiler.m4

@@ -51,6 +51,27 @@ fi
 ])# PGAC_C_INLINE
 
 
+# PGAC_C_PRINTF_ARCHETYPE
+# -----------------------
+# Set the format archetype used by gcc to check printf type functions.  We
+# prefer "gnu_printf", which includes what glibc uses, such as %m for error
+# strings and %lld for 64 bit long longs.  GCC 4.4 introduced it.  It makes a
+# dramatic difference on Windows.
+AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
+[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype,
+[ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+[extern int
+pgac_write(int ignore, const char *fmt,...)
+__attribute__((format(gnu_printf, 2, 3)));], [])],
+                  [pgac_cv_printf_archetype=gnu_printf],
+                  [pgac_cv_printf_archetype=printf])
+ac_c_werror_flag=$ac_save_c_werror_flag])
+AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype],
+                   [Define to gnu_printf if compiler supports it, else printf.])
+])# PGAC_PRINTF_ARCHETYPE
+
 
 # PGAC_TYPE_64BIT_INT(TYPE)
 # -------------------------

configure

@@ -10094,6 +10094,42 @@ _ACEOF
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype" >&5
+$as_echo_n "checking for printf format archetype... " >&6; }
+if ${pgac_cv_printf_archetype+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+extern int
+pgac_write(int ignore, const char *fmt,...)
+__attribute__((format(gnu_printf, 2, 3)));
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_printf_archetype=gnu_printf
+else
+  pgac_cv_printf_archetype=printf
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_printf_archetype" >&5
+$as_echo "$pgac_cv_printf_archetype" >&6; }
+
+cat >>confdefs.h <<_ACEOF
+#define PG_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype
+_ACEOF
+
+
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for flexible array members" >&5
 $as_echo_n "checking for flexible array members... " >&6; }

configure.in

@@ -1170,6 +1170,7 @@ fi
 m4_defun([AC_PROG_CC_STDC], []) dnl We don't want that.
 AC_C_BIGENDIAN
 PGAC_C_INLINE
+PGAC_PRINTF_ARCHETYPE
 AC_C_FLEXIBLE_ARRAY_MEMBER
 PGAC_C_SIGNED
 PGAC_C_FUNCNAME_SUPPORT

src/include/pg_config.h.in

@@ -718,6 +718,9 @@
 /* PostgreSQL major version as a string */
 #undef PG_MAJORVERSION
 
+/* Define to gnu_printf if compiler supports it, else printf. */
+#undef PG_PRINTF_ATTRIBUTE
+
 /* Define to 1 if "static inline" works without unwanted warnings from
    compilations where static inline functions are defined but not called. */
 #undef PG_USE_INLINE

src/include/pg_config_manual.h

@@ -187,22 +187,6 @@
  */
 #define MAX_RANDOM_VALUE  (0x7FFFFFFF)
 
-/*
- * Set the format style used by gcc to check printf type functions. We really
- * want the "gnu_printf" style set, which includes what glibc uses, such
- * as %m for error strings and %lld for 64 bit long longs. But not all gcc
- * compilers are known to support it, so we just use "printf" which all
- * gcc versions alive are known to support, except on Windows where
- * using "gnu_printf" style makes a dramatic difference. Maybe someday
- * we'll have a configure test for this, if we ever discover use of more
- * variants to be necessary.
- */
-#ifdef WIN32
-#define PG_PRINTF_ATTRIBUTE gnu_printf
-#else
-#define PG_PRINTF_ATTRIBUTE printf
-#endif
-
 /*
  * On PPC machines, decide whether to use the mutex hint bit in LWARX
  * instructions.  Setting the hint bit will slightly improve spinlock