[libc] Using `[[gnu::weak]]` declarations generates GOT entries

[petrhosek]

Using [[gnu::weak]] function declarations as is done in the following places results in GOT entries:

llvm-project/libc/src/stdlib/atexit.cpp

Line 19 in da98be1

[[gnu::weak]] extern void teardown_main_tls();

llvm-project/libc/src/stdlib/atexit.cpp

Lines 30 to 31 in da98be1

	if (teardown_main_tls)
	teardown_main_tls();

llvm-project/libc/src/stdlib/exit.cpp

Line 23 in da98be1

extern "C" [[gnu::weak]] void __cxa_thread_finalize();

llvm-project/libc/src/stdlib/exit.cpp

Lines 30 to 31 in da98be1

	if (__cxa_thread_finalize)
	__cxa_thread_finalize();

llvm-project/libc/src/stdlib/quick_exit.cpp

Line 19 in da98be1

[[gnu::weak]] extern void teardown_main_tls();

llvm-project/libc/src/stdlib/quick_exit.cpp

Lines 23 to 24 in da98be1

	if (teardown_main_tls)
	teardown_main_tls();

This is a problem for baremetal targets which use static linking.

We need to either restructure the code to avoid the use of weak symbols altogether, or provide empty weak definitions.

[llvmbot]

@llvm/issue-subscribers-libc

Author: Petr Hosek (petrhosek)

Details

Using `[[gnu::weak]]` function declarations as is done in the following places results in GOT entries:

llvm-project/libc/src/stdlib/atexit.cpp

Line 19 in da98be1

[[gnu::weak]] extern void teardown_main_tls();

llvm-project/libc/src/stdlib/atexit.cpp

Lines 30 to 31 in da98be1

	if (teardown_main_tls)
	teardown_main_tls();

llvm-project/libc/src/stdlib/exit.cpp

Line 23 in da98be1

extern "C" [[gnu::weak]] void __cxa_thread_finalize();

llvm-project/libc/src/stdlib/exit.cpp

Lines 30 to 31 in da98be1

	if (__cxa_thread_finalize)
	__cxa_thread_finalize();

llvm-project/libc/src/stdlib/quick_exit.cpp

Line 19 in da98be1

[[gnu::weak]] extern void teardown_main_tls();

llvm-project/libc/src/stdlib/quick_exit.cpp

Lines 23 to 24 in da98be1

	if (teardown_main_tls)
	teardown_main_tls();

This is a problem for baremetal targets which use static linking.

We need to either restructure the code to avoid the use of weak symbols altogether, or provide empty weak definitions.