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 5be8f0f08dcb53ae50bd6b9abe22cb42210680ed..c9946a8a44758d20e39e925b0ea473009a10baa0 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 be593e6e345ee92d251e897dc00e42bbdd8ca1ac..b0308a2b9e70e4b7ba74ef488027a23724f8a059 100755 (executable)
--- a/configure
+++ b/configure
@@ -14783,8 +14783,8 @@ _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
@@ -14844,7 +14844,97 @@ 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 575f615d46e4d1a989a98b9d99dff689a15125c1..9eefefd6804ebea6277d67ca4949a38aeccadfc4 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1665,6 +1665,7 @@ 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_STATIC_ASSERT
 PGAC_C_TYPEOF
 PGAC_C_TYPES_COMPATIBLE

diff --git a/meson.build b/meson.build
index a0003f33f00d46f855d0c76fe12b3b55d598ecb5..517f44d107cab90d8a1feda11867f01b7c8b3085 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -1802,6 +1802,8 @@ if cc.sizeof('bool', prefix: '#include <stdbool.h>', args: test_c_args) == 1
 endif
 
 
+# Select the format archetype to be used to check printf-type functions.
+#
 # Need to check a call with %m because netbsd supports gnu_printf but emits a
 # warning for each use of %m.
 printf_attributes = ['gnu_printf', '__syslog__', 'printf']
@@ -1816,11 +1818,24 @@ attrib_error_args = cc.get_supported_arguments('-Werror=format', '-Werror=ignore
 foreach a : printf_attributes
   if cc.compiles(testsrc.format(a),
       args: test_c_args + attrib_error_args, name: 'format ' + a)
-    cdata.set('PG_PRINTF_ATTRIBUTE', a)
+    cdata.set('PG_C_PRINTF_ATTRIBUTE', a)
     break
   endif
 endforeach
 
+# We need to repeat the test for C++ because gcc and clang prefer different
+# format archetypes.
+if llvm.found()
+  attrib_error_args = cpp.get_supported_arguments('-Werror=format', '-Werror=ignored-attributes')
+  foreach a : printf_attributes
+    if cpp.compiles(testsrc.format(a),
+        args: attrib_error_args, name: 'cppformat ' + a)
+      cdata.set('PG_CXX_PRINTF_ATTRIBUTE', a)
+      break
+    endif
+  endforeach
+endif
+
 
 if cc.has_function_attribute('visibility:default') and \
     cc.has_function_attribute('visibility:hidden')

diff --git a/src/include/c.h b/src/include/c.h
index a7258cce1fc04dfe4709e51cf2ea88333a34eca2..0e74ecce5bc4e1288fe1ea1ebc617a71e7a23c7a 100644 (file)
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -166,6 +166,16 @@
 #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 be27b8abe10f0d16050d5b9285934f1aafd6cb27..d06c49a894200cdca7feeeda0abe5352e72cfe52 100644 (file)
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -613,6 +613,14 @@
 /* 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
 
@@ -632,9 +640,6 @@
 /* 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