Revert "Distinguish printf-like functions that support %m from those that don't."

This reverts commit 3a60c8ff.  Buildfarm
results show that that caused a whole bunch of new warnings on platforms
where gcc believes the local printf to be non-POSIX-compliant.  This
problem outweighs the hypothetical-anyway possibility of getting warnings
for misuse of %m.  We could use gnu_printf archetype when we've substituted
src/port/snprintf.c, but that brings us right back to the problem of not
getting warnings for %m.

A possible answer is to attack it in the other direction by insisting
that %m support be included in printf's feature set, but that will take
more investigation.  In the meantime, revert the previous change, and
update the comment for PGAC_C_PRINTF_ARCHETYPE to more fully explain
what's going on.

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us

config/c-compiler.m4

@@ -19,12 +19,18 @@ fi])# PGAC_C_SIGNED
 
 # PGAC_C_PRINTF_ARCHETYPE
 # -----------------------
-# Set the format archetype used by gcc to check elog/ereport functions.
-# This should accept %m, whether or not the platform's printf does.
-# We use "gnu_printf" if possible, which does that, although in some cases
-# it might do more than we could wish.
+# Select the format archetype to be used by gcc to check printf-type functions.
+# We prefer "gnu_printf", which matches the features glibc supports, notably
+# %m, 'z' and 'll' width modifiers ('ll' only matters if int64 requires it),
+# and argument order control if we're doing --enable-nls.  On platforms where
+# the native printf doesn't have 'z'/'ll' or arg control, we replace it with
+# src/port/snprintf.c which does, so that the only potential mismatch here is
+# whether or not %m is supported.  We need that for elog/ereport, so we live
+# with the fact that erroneous use of %m in plain printf calls won't be
+# detected.  (It appears that many versions of gcc/clang wouldn't report it
+# even if told to check according to plain printf archetype, anyway.)
 AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
-[AC_CACHE_CHECK([for printf format archetype for %m], pgac_cv_printf_archetype,
+[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype,
 [ac_save_c_werror_flag=$ac_c_werror_flag
 ac_c_werror_flag=yes
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
@@ -34,8 +40,8 @@ __attribute__((format(gnu_printf, 2, 3)));], [])],
                   [pgac_cv_printf_archetype=gnu_printf],
                   [pgac_cv_printf_archetype=printf])
 ac_c_werror_flag=$ac_save_c_werror_flag])
-AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE_M], [$pgac_cv_printf_archetype],
-                   [Define as a format archetype that accepts %m, if available, else printf.])
+AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype],
+                   [Define to gnu_printf if compiler supports it, else printf.])
 ])# PGAC_PRINTF_ARCHETYPE
 
 

configure

@@ -13362,8 +13362,8 @@ _ACEOF
     ;;
 esac
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype for %m" >&5
-$as_echo_n "checking for printf format archetype for %m... " >&6; }
+{ $as_echo "$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
@@ -13394,7 +13394,7 @@ fi
 $as_echo "$pgac_cv_printf_archetype" >&6; }
 
 cat >>confdefs.h <<_ACEOF
-#define PG_PRINTF_ATTRIBUTE_M $pgac_cv_printf_archetype
+#define PG_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype
 _ACEOF
 
 

src/include/c.h

@@ -126,14 +126,10 @@
 /* GCC and XLC support format attributes */
 #if defined(__GNUC__) || defined(__IBMC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
-/* Use for functions wrapping stdio's printf, which often doesn't take %m: */
-#define pg_attribute_printf(f,a) __attribute__((format(printf, f, a)))
-/* Use for elog/ereport, which implement %m for themselves: */
-#define pg_attribute_printf_m(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE_M, f, a)))
+#define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
 #else
 #define pg_attribute_format_arg(a)
 #define pg_attribute_printf(f,a)
-#define pg_attribute_printf_m(f,a)
 #endif
 
 /* GCC, Sunpro and XLC support aligned, packed and noreturn */

src/include/pg_config.h.in

@@ -809,8 +809,8 @@
 /* PostgreSQL major version as a string */
 #undef PG_MAJORVERSION
 
-/* Define as a format archetype that accepts %m, if available, else printf. */
-#undef PG_PRINTF_ATTRIBUTE_M
+/* Define to gnu_printf if compiler supports it, else printf. */
+#undef PG_PRINTF_ATTRIBUTE
 
 /* PostgreSQL version as a string */
 #undef PG_VERSION

src/include/utils/elog.h

@@ -152,25 +152,25 @@ extern int	errcode(int sqlerrcode);
 extern int	errcode_for_file_access(void);
 extern int	errcode_for_socket_access(void);
 
-extern int	errmsg(const char *fmt,...) pg_attribute_printf_m(1, 2);
-extern int	errmsg_internal(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern int	errmsg(const char *fmt,...) pg_attribute_printf(1, 2);
+extern int	errmsg_internal(const char *fmt,...) pg_attribute_printf(1, 2);
 
 extern int errmsg_plural(const char *fmt_singular, const char *fmt_plural,
-			  unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
+			  unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
 
-extern int	errdetail(const char *fmt,...) pg_attribute_printf_m(1, 2);
-extern int	errdetail_internal(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern int	errdetail(const char *fmt,...) pg_attribute_printf(1, 2);
+extern int	errdetail_internal(const char *fmt,...) pg_attribute_printf(1, 2);
 
-extern int	errdetail_log(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern int	errdetail_log(const char *fmt,...) pg_attribute_printf(1, 2);
 
 extern int errdetail_log_plural(const char *fmt_singular,
 					 const char *fmt_plural,
-					 unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
+					 unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
 
 extern int errdetail_plural(const char *fmt_singular, const char *fmt_plural,
-				 unsigned long n,...) pg_attribute_printf_m(1, 4) pg_attribute_printf_m(2, 4);
+				 unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
 
-extern int	errhint(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern int	errhint(const char *fmt,...) pg_attribute_printf(1, 2);
 
 /*
  * errcontext() is typically called in error context callback functions, not
@@ -184,7 +184,7 @@ extern int	errhint(const char *fmt,...) pg_attribute_printf_m(1, 2);
 
 extern int	set_errcontext_domain(const char *domain);
 
-extern int	errcontext_msg(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern int	errcontext_msg(const char *fmt,...) pg_attribute_printf(1, 2);
 
 extern int	errhidestmt(bool hide_stmt);
 extern int	errhidecontext(bool hide_ctx);
@@ -243,13 +243,13 @@ extern int	getinternalerrposition(void);
 #endif							/* HAVE__VA_ARGS */
 
 extern void elog_start(const char *filename, int lineno, const char *funcname);
-extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf_m(2, 3);
+extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf(2, 3);
 
 
 /* Support for constructing error strings separately from ereport() calls */
 
 extern void pre_format_elog_string(int errnumber, const char *domain);
-extern char *format_elog_string(const char *fmt,...) pg_attribute_printf_m(1, 2);
+extern char *format_elog_string(const char *fmt,...) pg_attribute_printf(1, 2);
 
 
 /* Support for attaching context information to error reports */
@@ -428,9 +428,9 @@ extern void set_syslog_parameters(const char *ident, int facility);
 #endif
 
 /*
- * Write errors to stderr (or by comparable means when stderr is not
- * available).  Used before ereport/elog can be used safely (memory context,
- * GUC load etc).  Note that this does *not* accept "%m".
+ * Write errors to stderr (or by equal means when stderr is
+ * not available). Used before ereport/elog can be used
+ * safely (memory context, GUC load etc)
  */
 extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);