Allow PG_PRINTF_ATTRIBUTE to be different in C and C++ code.

Although clang claims to be compatible with gcc's printf format
archetypes, this appears to be a falsehood: it likes __syslog__
(which gcc does not, on most platforms) and doesn't accept
gnu_printf.  This means that if you try to use gcc with clang++
or clang with g++, you get compiler warnings when compiling
printf-like calls in our C++ code.  This has been true for quite
awhile, but it's gotten more annoying with the recent appearance
of several buildfarm members that are configured like this.

To fix, run separate probes for the format archetype to use with the
C and C++ compilers, and conditionally define PG_PRINTF_ATTRIBUTE
depending on __cplusplus.

(We could alternatively insist that you not mix-and-match C and
C++ compilers; but if the case works otherwise, this is a poor
reason to insist on that.)

This commit back-patches 0909380e4 into supported branches.

Discussion: https://postgr.es/m/986485.1764825548@sss.pgh.pa.us
Discussion: https://postgr.es/m/3988414.1771950285@sss.pgh.pa.us
Backpatch-through: 14-18

diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index d3562d6feee52f7e95db559c661baea182bb0b2a..f0744482e7e96a791f35381b0c03ad18768a08f2 100644 (file)
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -7,10 +7,10 @@
 # Select the format archetype to be used by gcc to check printf-type functions.
 # We prefer "gnu_printf", as that most closely matches the features supported
 # by src/port/snprintf.c (particularly the %m conversion spec).  However,
-# on some NetBSD versions, that doesn't work while "__syslog__" does.
-# If all else fails, use "printf".
+# on clang and on some NetBSD versions, that doesn't work while "__syslog__"
+# does.  If all else fails, use "printf".
 AC_DEFUN([PGAC_PRINTF_ARCHETYPE],
-[AC_CACHE_CHECK([for printf format archetype], pgac_cv_printf_archetype,
+[AC_CACHE_CHECK([for C printf format archetype], pgac_cv_printf_archetype,
 [pgac_cv_printf_archetype=gnu_printf
 PGAC_TEST_PRINTF_ARCHETYPE
 if [[ "$ac_archetype_ok" = no ]]; then
@@ -20,8 +20,8 @@ if [[ "$ac_archetype_ok" = no ]]; then
     pgac_cv_printf_archetype=printf
   fi
 fi])
-AC_DEFINE_UNQUOTED([PG_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype],
-[Define to best printf format archetype, usually gnu_printf if available.])
+AC_DEFINE_UNQUOTED([PG_C_PRINTF_ATTRIBUTE], [$pgac_cv_printf_archetype],
+[Define to best C printf format archetype, usually gnu_printf if available.])
 ])# PGAC_PRINTF_ARCHETYPE
 
 # Subroutine: test $pgac_cv_printf_archetype, set $ac_archetype_ok to yes or no
@@ -92,6 +92,42 @@ undefine([Ac_cachevar])dnl
 ])# PGAC_TYPE_64BIT_INT
 
 
+# PGAC_CXX_PRINTF_ARCHETYPE
+# -------------------------
+# Because we support using gcc as C compiler with clang as C++ compiler,
+# we have to be prepared to use different printf archetypes in C++ code.
+# So, do the above test all over in C++.
+AC_DEFUN([PGAC_CXX_PRINTF_ARCHETYPE],
+[AC_CACHE_CHECK([for C++ printf format archetype], pgac_cv_cxx_printf_archetype,
+[pgac_cv_cxx_printf_archetype=gnu_printf
+PGAC_TEST_CXX_PRINTF_ARCHETYPE
+if [[ "$ac_archetype_ok" = no ]]; then
+  pgac_cv_cxx_printf_archetype=__syslog__
+  PGAC_TEST_CXX_PRINTF_ARCHETYPE
+  if [[ "$ac_archetype_ok" = no ]]; then
+    pgac_cv_cxx_printf_archetype=printf
+  fi
+fi])
+AC_DEFINE_UNQUOTED([PG_CXX_PRINTF_ATTRIBUTE], [$pgac_cv_cxx_printf_archetype],
+[Define to best C++ printf format archetype, usually gnu_printf if available.])
+])# PGAC_CXX_PRINTF_ARCHETYPE
+
+# Subroutine: test $pgac_cv_cxx_printf_archetype, set $ac_archetype_ok to yes or no
+AC_DEFUN([PGAC_TEST_CXX_PRINTF_ARCHETYPE],
+[ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+AC_LANG_PUSH(C++)
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+[extern void pgac_write(int ignore, const char *fmt,...)
+__attribute__((format($pgac_cv_cxx_printf_archetype, 2, 3)));],
+[pgac_write(0, "error %s: %m", "foo");])],
+                  [ac_archetype_ok=yes],
+                  [ac_archetype_ok=no])
+AC_LANG_POP([])
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+])# PGAC_TEST_CXX_PRINTF_ARCHETYPE
+
+
 # PGAC_TYPE_128BIT_INT
 # --------------------
 # Check if __int128 is a working 128 bit integer type, and if so

diff --git a/configure b/configure
index b6e0edba8187137d69473088fdb7390c9a8c80f7..77f8372cb7e867bd05b9285821b98f23f2fbf4b0 100755 (executable)
--- a/configure
+++ b/configure
@@ -14812,8 +14812,8 @@ _ACEOF
     ;;
 esac
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype" >&5
-$as_echo_n "checking for printf format archetype... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C printf format archetype" >&5
+$as_echo_n "checking for C printf format archetype... " >&6; }
 if ${pgac_cv_printf_archetype+:} false; then :
   $as_echo_n "(cached) " >&6
 else
@@ -14873,7 +14873,97 @@ fi
 $as_echo "$pgac_cv_printf_archetype" >&6; }
 
 cat >>confdefs.h <<_ACEOF
-#define PG_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype
+#define PG_C_PRINTF_ATTRIBUTE $pgac_cv_printf_archetype
+_ACEOF
+
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C++ printf format archetype" >&5
+$as_echo_n "checking for C++ printf format archetype... " >&6; }
+if ${pgac_cv_cxx_printf_archetype+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_cv_cxx_printf_archetype=gnu_printf
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+extern void pgac_write(int ignore, const char *fmt,...)
+__attribute__((format($pgac_cv_cxx_printf_archetype, 2, 3)));
+int
+main ()
+{
+pgac_write(0, "error %s: %m", "foo");
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  ac_archetype_ok=yes
+else
+  ac_archetype_ok=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+
+if [ "$ac_archetype_ok" = no ]; then
+  pgac_cv_cxx_printf_archetype=__syslog__
+  ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+extern void pgac_write(int ignore, const char *fmt,...)
+__attribute__((format($pgac_cv_cxx_printf_archetype, 2, 3)));
+int
+main ()
+{
+pgac_write(0, "error %s: %m", "foo");
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  ac_archetype_ok=yes
+else
+  ac_archetype_ok=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+
+  if [ "$ac_archetype_ok" = no ]; then
+    pgac_cv_cxx_printf_archetype=printf
+  fi
+fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_cxx_printf_archetype" >&5
+$as_echo "$pgac_cv_cxx_printf_archetype" >&6; }
+
+cat >>confdefs.h <<_ACEOF
+#define PG_CXX_PRINTF_ATTRIBUTE $pgac_cv_cxx_printf_archetype
 _ACEOF
 
 

diff --git a/configure.ac b/configure.ac
index 9ff5322d908c825f2dbdbf0334da1011d3b35d20..b84fa574860b2d3d31914f7dc9d1dc3baeb31960 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1634,6 +1634,7 @@ m4_defun([AC_PROG_CC_STDC], []) dnl We don't want that.
 AC_C_BIGENDIAN
 AC_C_INLINE
 PGAC_PRINTF_ARCHETYPE
+PGAC_CXX_PRINTF_ARCHETYPE
 PGAC_C_FUNCNAME_SUPPORT
 PGAC_C_STATIC_ASSERT
 PGAC_C_TYPEOF

diff --git a/src/include/c.h b/src/include/c.h
index cc19c23fb672d89bd4174354f756f64af7913681..61af588de016c4cad5ea61665add043d907be18b 100644 (file)
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -155,6 +155,16 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
+/*
+ * Our C and C++ compilers may have different ideas about which printf
+ * archetype best represents what src/port/snprintf.c can do.
+ */
+#ifndef __cplusplus
+#define PG_PRINTF_ATTRIBUTE PG_C_PRINTF_ATTRIBUTE
+#else
+#define PG_PRINTF_ATTRIBUTE PG_CXX_PRINTF_ATTRIBUTE
+#endif
+
 /* GCC and XLC support format attributes */
 #if defined(__GNUC__) || defined(__IBMC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))

diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 906c7893553a22a3383a7d47d0cf8c6987ff3b9c..cdb98885a298a8c5720e134ef819e338a3f61819 100644 (file)
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -814,6 +814,14 @@
 /* Define to the version of this package. */
 #undef PACKAGE_VERSION
 
+/* Define to best C++ printf format archetype, usually gnu_printf if
+   available. */
+#undef PG_CXX_PRINTF_ATTRIBUTE
+
+/* Define to best C printf format archetype, usually gnu_printf if available.
+   */
+#undef PG_C_PRINTF_ATTRIBUTE
+
 /* Define to the name of a signed 128-bit integer type. */
 #undef PG_INT128_TYPE
 
@@ -833,9 +841,6 @@
 /* PostgreSQL minor version number */
 #undef PG_MINORVERSION_NUM
 
-/* Define to best printf format archetype, usually gnu_printf if available. */
-#undef PG_PRINTF_ATTRIBUTE
-
 /* Define to 1 to use <stdbool.h> to define type bool. */
 #undef PG_USE_STDBOOL