lld -Bstatic fails to link because _end is undefined #25902
Comments
|
assigned to @igorkudrin |
|
Repro: % objdump -t ./end | grep _end % ./clang end.c -fuse-ld=lld2 -o blah -static % cat end.c int main(void) |
|
These linker-created symbols are similar to __init_array_end and the like but are different in such way that they are relative to segments. __init_array_end and the like are defined for sections. We cannot calculate the address of _end symbol until we bin all sections into segments. But before doing that, all symbols need to be defined and available since we need to create GOT/PLT segments contents. So I think this needs to be done in two-pass. In the first pass, we add _end symbol with a dummy address 0, and backfill that address once we create segments. |
|
Should be fixed in r253637. |
Extended Description
The first bug found while building world on FreeBSD =)
sbrk() access _end (directly!) to understand where .bss ends.
The linker should probably insert that in the generated executable (at least when -Bstatic is used). It seems gold doesn't strip the symbol even if not referenced.
% ./clang sbrk.c -fuse-ld=lld2 -o sbrs -static
undefined symbol: _end in sbrk.o
clang-3.8: error: linker command failed with exit code 1 (use -v to see invocation)
Linker invocation:
"/exps/llvm-lld/build/bin/./ld.lld2" -Bstatic -o sbrs /usr/lib/crt1.o /usr/lib/crti.o /usr/lib/crtbeginT.o -L/usr/lib /tmp/sbrk-63b6db.o -lgcc -lgcc_eh -lc -lgcc -lgcc_eh /usr/lib/crtend.o /usr/lib/crtn.o
% cat sbrk.c
#include <sys/types.h>
#include <unistd.h>
int
main(void)
{
void *me = sbrk(42);
return (0);
}
The text was updated successfully, but these errors were encountered: