https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81980
Bug ID: 81980 Summary: Spurious -Wmissing-format-attribute warning in 32-bit mode Product: gcc Version: 7.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: sgunderson at bigfoot dot com Target Milestone: --- Hi, The following (reduced) code gives a warning if and only if I add -m32: atum17:~> cat test.c #include <stdarg.h> char a; void set_message(const char *fmt, va_list ap) __attribute__((format(printf, 1, 0))); void set_message_by_errcode(va_list ap) { set_message(&a, ap); } atum17:~> gcc -Wmissing-format-attribute -c test.c atum17:~> gcc -Wmissing-format-attribute -c test.c -m32 test.cc: In function ‘void set_message_by_errcode(va_list)’: test.cc:6:61: warning: function ‘void set_message_by_errcode(va_list)’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format] void set_message_by_errcode(va_list ap) { set_message(&a, ap); } ^ I believe the warning is spurious, since there's no way you could construct a valid printf format attribute for set_message_by_errcode (it doesn't take in a string parameter). This holds for both C and C++. atum17:~> gcc -v Using built-in specs. COLLECT_GCC=/usr/bin/gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper OFFLOAD_TARGET_NAMES=nvptx-none OFFLOAD_TARGET_DEFAULT=1 Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Debian 7.2.0-1' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-7 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 7.2.0 (Debian 7.2.0-1)