https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93609
Bug ID: 93609 Summary: gcc -flto -fno-comon places symbols into ".text" section Product: gcc Version: 9.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: lto Assignee: unassigned at gcc dot gnu.org Reporter: slyfox at inbox dot ru CC: marxin at gcc dot gnu.org Target Milestone: --- It's an upstream version of https://bugs.gentoo.org/708340 where libtool was not able to detect symbol type based on gcc-nm output. Here is the small reproducer: // cat a.c char nm_test_var; void nm_test_func(void){} $ gcc -c a.c -o a.o -fcommon -flto && gcc-nm a.o 00000000 T nm_test_func 00000000 C nm_test_var T/C - good $ gcc -c a.c -o a.o -fno-common -flto && gcc-nm a.o 00000000 T nm_test_func 00000000 T nm_test_var T/C - bad For comparison here is non-lto version: $ gcc -c a.c -o a.o -fcommon && gcc-nm a.o 0000000000000000 T nm_test_func 0000000000000001 C nm_test_var T/C - good $ gcc -c a.c -o a.o -fno-common && gcc-nm a.o 0000000000000000 T nm_test_func 0000000000000000 B nm_test_var T/B - good libtool only cares if a symbol is reportes as T or not: http://git.savannah.gnu.org/cgit/libtool.git/tree/m4/libtool.m4#n3999 lt_cv_sys_global_symbol_to_cdecl="sed -n"\ $lt_cdecl_hook\ " -e 's/^T .* \(.*\)$/extern int \1();/p'"\ " -e 's/^$symcode$symcode* .* \(.*\)$/extern char \1;/p'" Is it fair to say that it's a gcc (or binutils?) bug? Reproducing on gcc-9.2.0 and gcc-master. $ LANG=C gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/9.2.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /dev/shm/portage/sys-devel/gcc-9.2.0-r3/work/gcc-9.2.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/9.2.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 9.2.0-r3 p4' --disable-esp --enable-libstdcxx-time --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --enable-multilib --with-multilib-list=m32,m64 --disable-altivec --disable-fixed-point --enable-targets=all --enable-libgomp --disable-libmudflap --disable-libssp --disable-systemtap --enable-vtable-verify --enable-lto --without-isl --enable-default-pie --enable-default-ssp Thread model: posix gcc version 9.2.0 (Gentoo 9.2.0-r3 p4)