From acfc107a50344b100b9ea492678928acc047c6ae Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Fri, 4 Oct 2013 15:35:01 +0530 Subject: Fix weak/strong attribute of __errno_location and it's __GI alias A simple statically linked hello world program was segfaulting for ARC in linuxthreads.old configuration (although the root casue applies cross-arch for NPTL as well as linuxthreads.old as described) The crash was due to branch to NULL in _stdio_init 0001026c <_stdio_init>: 1026c: push_s blink 1026e: st.a r13,[sp,-8] 10272: bl.d 0 --> supposed call to __errno_location The call was NOT getting patched to libc internal only alias __GI___errno_location, because it was weak while it's exported cousin, __errno_location was strong/normal. arc-linux-uclibc-nm libc/misc/internals/__errno_location.os 00000000 W __GI___errno_location 00000000 T __errno_location This is exactly opposite to what is expected. Quoting Peter S. Mazinger, commit 87936cd013041 "errno and *_init cleanup" | The rule adopted: | for enabled threads we make in libc the __GI_x() variants strong, x() weak | and (should) provide another strong x() in libpthread. | If threads are disabled, even the __GI_x() variants are weak. With the fix, we see the right settings as below 00000000 T __GI___errno_location 00000000 W __errno_location Note that problem won't show up in a static busybox build as it references errno and that seems to elide the issue. I can confirm the same/more issues with latest ARM buildroot builds w/o my fix. (1). linuxthreads.old (broken just like ARC) arm-linux-nm uclibc-snapshot/libc/misc/internals/__errno_location.os 00000000 W __GI___errno_location 00000000 T __errno_location But presumably the issue there is NOT catestrophic because ARM linker is likely smarter and patches a NOP instead of NULL branch. 00008388 <_stdio_init>: 8388: e92d4038 push {r3, r4, r5, lr} 838c: e320f000 nop {0} (2) NPTL build (exported version is not weak) 00000000 T __GI___errno_location 00000000 T __errno_location This causes a static link with libpthread and test program referencing errno to fail to link. #include int main(void) { printf("%d\n", errno); } arm-linux-gcc -static -pthread -o tst tst.o arm-buildroot-linux-uclibcgnueabi/sysroot/usr/lib/libc.a(__errno_location.os): In function `__errno_location': __errno_location.c:(.text+0x0): multiple definition of `__errno_location' arm-buildroot-linux-uclibcgnueabi/sysroot/usr/lib/libpthread.a (errno_location.os):errno_location.c:(.text+0x0): first defined here Signed-off-by: Vineet Gupta Cc: Baruch Siach Signed-off-by: Bernhard Reutner-Fischer --- libc/sysdeps/linux/common/bits/errno.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'libc/sysdeps/linux/common') diff --git a/libc/sysdeps/linux/common/bits/errno.h b/libc/sysdeps/linux/common/bits/errno.h index 7ef1b9440..777338fb1 100644 --- a/libc/sysdeps/linux/common/bits/errno.h +++ b/libc/sysdeps/linux/common/bits/errno.h @@ -43,7 +43,7 @@ /* Function to get address of global `errno' variable. */ extern int *__errno_location (void) __THROW __attribute__ ((__const__)); # ifdef _LIBC -# ifndef __UCLIBC_HAS_TLS__ +# if !defined(__UCLIBC_HAS_TLS__) && !defined(__UCLIBC_HAS_THREADS__) extern int weak_const_function *__errno_location(void); # endif # endif -- cgit v1.2.3