--trace-symbol flag affects .symver

[brandonfoong]

Using the following program,

#include <pthread.h>
#include <stddef.h>

__asm__(".symver pthread_join,pthread_join@GLIBC_2.2.5");

void* my_thread_start(void*) { return NULL; }

int main() {
    pthread_t my_thread;
    pthread_create(&my_thread, NULL, &my_thread_start, NULL);
    pthread_join(my_thread, NULL);
    return 0;
}

If I compile with -fuse-ld=mold and use nm -D to display the dynamic imports, I get

                 U __cxa_finalize@GLIBC_2.2.5
                 U __libc_start_main@GLIBC_2.34
                 U pthread_create@GLIBC_2.34
                 U pthread_join@GLIBC_2.2.5
                 U __stack_chk_fail@GLIBC_2.4

as expected.

However, if I add -Wl,-y,pthread_join@GLIBC_2.2.5, nm -D shows

                 U __cxa_finalize@GLIBC_2.2.5
                 U __libc_start_main@GLIBC_2.34
                 U pthread_create@GLIBC_2.34
                 U pthread_join@GLIBC_2.2.5@GLIBC_2.2.5
                 U __stack_chk_fail@GLIBC_2.4

Strangely, I could only get this to occur in Ubuntu 22.04, but not 20.04, which may be caused by glibc introducing a new default version to pthread_join.

[brandonfoong]

It may be caused by this line adding foo@VER -> foo@VER into the symbol map

mold/elf/main.cc

Lines 382 to 383 in 0702d41

	for (std::string_view arg : ctx.arg.trace_symbol)
	get_symbol(ctx, arg)->is_traced = true;

when we actually want versioned symbols to map foo@VER -> foo

mold/elf/input-files.cc

Lines 1327 to 1329 in 0702d41

	std::string_view mangled_name = save_string(
	ctx, std::string(name) + "@" + std::string(version_strings[ver]));
	this->symbols.push_back(get_symbol(ctx, mangled_name, name));

[rui314]

Thank you for your report! The above change should fix the issue.