On Sun Jan 21, 2024 at 11:11 PM CST, Sutou Kouhei wrote:
Hi,
I'm an extension developer. If I use PostgreSQL built with
Meson, I get the following warning:
cc1: warning: '-Wformat-security' ignored without '-Wformat'
[-Wformat-security]
Because "pg_config --cflags" includes -Wformat-security but
doesn't include -Wformat.
Can we specify -Wformat as a common warning flag too? If we
do it, "pg_config --cflags" includes both of
-Wformat-security and -Wformat. So I don't get the warning.
The GCC documentation[0] says the following:
If -Wformat is specified, also warn about uses of format functions
that represent possible security problems. At present, this warns
about calls to printf and scanf functions where the format string is
not a string literal and there are no format arguments, as in printf
(foo);. This may be a security hole if the format string came from
untrusted input and contains ‘%n’. (This is currently a subset of what
-Wformat-nonliteral warns about, but in future warnings may be added
to -Wformat-security that are not included in -Wformat-nonliteral.)
It sounds like a legitimate issue. I have confirmed the issue exists
with a pg_config compiled with Meson. I can also confirm that this issue
exists in the autotools build.
Here is a v2 of your patch which includes the fix for autotools. I will
mark this "Ready for Committer" in the commitfest. Thanks!
[0]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
--
Tristan Partin
Neon (https://neon.tech)
From bce0f70f866bb0e3f8fb8eb14c05bbbdd27c51f2 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <k...@clear-code.com>
Date: Mon, 22 Jan 2024 13:51:58 +0900
Subject: [PATCH v2] Add -Wformat to common warning flags
We specify -Wformat-security as a common warning flag explicitly. GCC
requires -Wformat to be added for -Wformat-security to take effect. If
-Wformat-security is used without -Wformat, GCC shows the following
warning:
cc1: warning: '-Wformat-security' ignored without '-Wformat' [-Wformat-security]
Co-authored-by: Sutou Kouhei <k...@clear-code.com>
---
configure | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++
configure.ac | 3 ++
meson.build | 2 ++
3 files changed, 97 insertions(+)
diff --git a/configure b/configure
index 36feeafbb23..eafab247e1d 100755
--- a/configure
+++ b/configure
@@ -5985,6 +5985,98 @@ if test x"$pgac_cv_prog_CXX_cxxflags__Wshadow_compatible_local" = x"yes"; then
fi
+ # -Wformat-security requires -Wformat, so check for it
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -Wformat, for CFLAGS" >&5
+$as_echo_n "checking whether ${CC} supports -Wformat, for CFLAGS... " >&6; }
+if ${pgac_cv_prog_CC_cflags__Wformat+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS} -Wformat"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+int
+main ()
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+ pgac_cv_prog_CC_cflags__Wformat=yes
+else
+ pgac_cv_prog_CC_cflags__Wformat=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__Wformat" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__Wformat" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__Wformat" = x"yes"; then
+ CFLAGS="${CFLAGS} -Wformat"
+fi
+
+
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -Wformat, for CXXFLAGS" >&5
+$as_echo_n "checking whether ${CXX} supports -Wformat, for CXXFLAGS... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__Wformat+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS} -Wformat"
+ac_save_cxx_werror_flag=$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.$ac_ext
+/* end confdefs.h. */
+
+int
+main ()
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ pgac_cv_prog_CXX_cxxflags__Wformat=yes
+else
+ pgac_cv_prog_CXX_cxxflags__Wformat=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=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__Wformat" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__Wformat" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__Wformat" = x"yes"; then
+ CXXFLAGS="${CXXFLAGS} -Wformat"
+fi
+
+
# This was included in -Wall/-Wformat in older GCC versions
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -Wformat-security, for CFLAGS" >&5
diff --git a/configure.ac b/configure.ac
index 57f734879e1..87a8860ecca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -527,6 +527,9 @@ if test "$GCC" = yes -a "$ICC" = no; then
PGAC_PROG_CXX_CFLAGS_OPT([-Wcast-function-type])
PGAC_PROG_CC_CFLAGS_OPT([-Wshadow=compatible-local])
PGAC_PROG_CXX_CFLAGS_OPT([-Wshadow=compatible-local])
+ # -Wformat-security requires -Wformat, so check for it
+ PGAC_PROG_CC_CFLAGS_OPT([-Wformat])
+ PGAC_PROG_CXX_CFLAGS_OPT([-Wformat])
# This was included in -Wall/-Wformat in older GCC versions
PGAC_PROG_CC_CFLAGS_OPT([-Wformat-security])
PGAC_PROG_CXX_CFLAGS_OPT([-Wformat-security])
diff --git a/meson.build b/meson.build
index 85788f9dd8f..717fdc4746b 100644
--- a/meson.build
+++ b/meson.build
@@ -1826,6 +1826,8 @@ common_warning_flags = [
'-Wimplicit-fallthrough=3',
'-Wcast-function-type',
'-Wshadow=compatible-local',
+ # -Wformat-security requires -Wformat, so check for it
+ '-Wformat',
# This was included in -Wall/-Wformat in older GCC versions
'-Wformat-security',
]
--
Tristan Partin
Neon (https://neon.tech)
