https://sourceware.org/bugzilla/show_bug.cgi?id=23935
Bug ID: 23935
Summary: ld.bfd does not rescan fat LTO archives to resolve
plugin-added references
Product: binutils
Version: 2.32 (HEAD)
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: vlad at ispras dot ru
Target Milestone: ---
#!/bin/sh -
cat > prog.c << EOF
#include <stdio.h>
int main() { printf("hi\n"); return 0; }
EOF
cat > libfoo.c << EOF
#include <stdio.h>
int puts(const char *s) { return 0; }
EOF
gcc -c -flto -fno-builtin -ffat-lto-objects libfoo.c -o libfoo.o
ar rcs libfoo.a libfoo.o
# gold="-fuse-ld=gold"
gcc -c -flto prog.c -o prog.o
gcc $gold -Wl,-emain -L. -static -nostdlib prog.o -lfoo
################################################################################
>From <https://sourceware.org/ml/binutils/2014-08/msg00025.html> I gather that
in
the presence of LTO recompiled objects, the archives are supposed to be
rescanned automatically. This does not happen in the example above.
When LTOing prog.o, GCC transforms the printf call to a puts call. I expect
this
new call to see a resolution in libfoo.a. And it happens indeed, if one uses
Gold. Not so for the BFD linker:
/usr/bin/ld: /tmp/ccvITLI4.ltrans0.ltrans.o: in function `main':
<artificial>:(.text+0xc): undefined reference to `puts'
Notice the -ffat-lto-objects switch. Without it, libfoo.a would contain only
LTO bytecode and both linkers would error out. It seems, the logic is off
somewhere taking "contains LTO bytecode" for "contains only LTO bytecode".
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