https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90229
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to H.J. Lu from comment #4)
> I can't reproduce it with binutils master branch and GCC 9:
>
> [hjl@gnu-cfl-1 pr90229]$ cat x.ii
> extern int FLAGS_verbose;
> extern "C" void pthread_create(void);
>
> void a(const char *b...) {
> if (FLAGS_verbose) {
> __builtin_va_list ap;
> __builtin_va_start(ap, b);
> }
> }
> void a() { pthread_create(); }
> int main() { a(""); return 0; }
> [hjl@gnu-cfl-1 pr90229]$ cat lib.ii
> int FLAGS_verbose;
> [hjl@gnu-cfl-1 pr90229]$ make
> /export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/ -B./
> -g -flto -c -o x.o x.ii
> /export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/ -B./
> -g -c -o lib.o lib.ii
> /export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/ -B./
> -shared -g -o libx.so lib.o
> /export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/tools-build/gcc-wip-debug/build-x86_64-linux/gcc/ -B./
> -pthread -g -o x x.o libx.so -Wl,--as-needed
> [hjl@gnu-cfl-1 pr90229]$
I can confirm that with current trunk of both GCC and bintuils. You used a bit
different
build steps:
1) one needs g++ for: -shared -g -o libx.so lib.o
2) you forgot to add -O and -flto to last command line
So please use following steps:
bash -x ./todo
+ gcc -g -c -o lib.o lib.ii
+ g++ -shared -g -o libx.so lib.o
+ gcc -g -flto -c -o x.o x.ii -O
+ gcc -flto -O -pthread -g -o x x.ii libx.so -Wl,--as-needed
/home/marxin/bin/binutils/bin/ld: /home/marxin/bin/gcc/lib64//libstdc++.so.6:
undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
