http://sourceware.org/bugzilla/show_bug.cgi?id=12772
Summary: relocations from discarded sections stay
Product: binutils
Version: 2.22 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: unassig...@sources.redhat.com
ReportedBy: m...@suse.de
(this got initially reported into Novell bugzilla #694266).
Compile this with the following compile command on x86_64-linux:
# g++ -O3 -Wl,-gc-sections -fpic -shared \
-fdata-sections -ffunction-sections \
-fvisibility-inlines-hidden -fvisibility=hidden \
-o test.so test.cpp
# cat test.cpp
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
extern "C" int __attribute__((visibility("default"))) func(char *ptr)
{
static const char g_const[] = { 1, 1, 0 };
memcpy(ptr, g_const, 3);
return 0;
}
extern "C" char *func2(char *ptr)
{
static char buf[4096];
if (!getcwd(buf, sizeof(buf)))
buf[0] = 0;
#define STR "test_string"
memcpy(ptr, STR, sizeof(STR));
return buf;
}
Note that func2 will be hidden, and as it's unreferenced the .text.func2
section will be discarded, as will be the .bss._ZZ5func2E3buf section:
# ...
./ld/ld-new: Removing unused section '.text.func2' in file
'show-link-discard-fail.o'
./ld/ld-new: Removing unused section '.bss._ZZ5func2E3buf' in file
'show-link-discard-fail.o'
But the relocation to getcwd (or better it's default decorated variant
getcwd@@GLIBC_2.2.5) will stay and transferred into the output file.
It should have been discarded too. In fact the gc_sweep_hook on x86_64
for instance does lower the PLT count for this reloc, and hence seems
to assume that it really won't be emitted. But alas, it is.
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