https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105133
Bug ID: 105133
Summary: lto/gold: lto failed to link --start-lib/--end-lib in
gold
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: luoxhu at gcc dot gnu.org
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Hi, linker gold supports --start-lib and --end-lib to "mimics the
semantics of static libraries, but without needing to actually create
the archive file."(https://reviews.llvm.org/D66848). Sometimes large
application may introduce multiple libraries from different repositories with
same source code, they would be linked into one binary finally, recently I
suffered from a link error with gold as linker and reduced an example as below:
cat hello.c
extern int hello(int a);
int main(void)
{
return 0; /* hello(10); */
}
cat ./B/libhello.c
#include <stdio.h>
int hello(int a)
{
puts("Hello");
return 0;
}
cat ./C/libhello.c
#include <stdio.h>
int hello(int a)
{
puts("Hello");
return 0;
}
(1) NON lto link with gold is OK:
gcc -O2 -o ./B/libhello.c.o -c ./B/libhello.c
gcc-ar qc ./B/libhello.a ./B/libhello.c.o
gcc-ranlib ./B/libhello.a
gcc -O2 -o ./C/libhello.c.o -c ./C/libhello.c
gcc-ar qc ./C/libhello.a ./C/libhello.c.o
gcc-ranlib ./C/libhello.a
gcc hello.c -o hello.o -c -O2
gcc -o hellow hello.o -Wl,--start-lib ./B/libhello.c.o -Wl,--end-lib
-Wl,--start-lib ./C/libhello.c.o -Wl,--end-lib -O2 -fuse-ld=gold
(2) lto link with gold fails with redefinition:
gcc -O2 -flto -o ./B/libhello.c.o -c ./B/libhello.c
gcc-ar qc ./B/libhello.a ./B/libhello.c.o
gcc-ranlib ./B/libhello.a
gcc -O2 -flto -o ./C/libhello.c.o -c ./C/libhello.c
gcc-ar qc ./C/libhello.a ./C/libhello.c.o
gcc-ranlib ./C/libhello.a
gcc hello.c -o hello.o -c -O2 -flto
gcc -o hellow hello.o -Wl,--start-lib ./B/libhello.c.o -Wl,--end-lib
-Wl,--start-lib ./C/libhello.c.o -Wl,--end-lib -O2 -flto -fuse-ld=gold
./B/libhello.c:5:5: error: 'hello' has already been defined
5 | int hello(int a)
| ^
./B/libhello.c:5:5: note: previously defined here
lto1: fatal error: errors during merging of translation units
compilation terminated.
lto-wrapper: fatal error: gcc returned 1 exit status
compilation terminated.
/usr/bin/ld.gold: fatal error: lto-wrapper failed
collect2: error: ld returned 1 exit status
This error happens at function gcc/lto/lto-symtab.c:lto_symtab_resolve_symbols,
simply remove the error_at line could work, but this may be not a reasonable
fix.
/* Find the single non-replaceable prevailing symbol and
diagnose ODR violations. */
for (e = first; e; e = e->next_sharing_asm_name)
{
if (!lto_symtab_resolve_can_prevail_p (e))
continue;
/* If we have a non-replaceable definition it prevails. */
if (!lto_symtab_resolve_replaceable_p (e))
{
if (prevailing)
{
error_at (DECL_SOURCE_LOCATION (e->decl),
"%qD has already been defined", e->decl);
inform (DECL_SOURCE_LOCATION (prevailing->decl),
"previously defined here");
}
prevailing = e;
}
}
cat hellow.res
3
hello.o 2
192 ccb9165e03755470 PREVAILING_DEF main
197 ccb9165e03755470 PREVAILING_DEF_IRONLY s
./B/libhello.c.o 1
205 68e0b97e93a52d7a PREEMPTED_REG hello
./C/libhello.c.o 1
205 18fe2d3482bfb511 PREEMPTED_REG hello
Secondly, If call hello(10) in hello.c , there will be NO error reported out.
The difference is the resolution type is changed from PREEMPTED_REG to
RESOLVED_IR/PREVAILING_DEF_IRONLY.
3
hello.o 3
192 19ef867d12f62129 PREVAILING_DEF main
197 19ef867d12f62129 PREVAILING_DEF_IRONLY s
201 19ef867d12f62129 RESOLVED_IR hello
./B/libhello.c.o 1
205 23c5c855935478ce PREVAILING_DEF_IRONLY hello
./C/libhello.c.o 1
205 abbf050f5c23b448 PREEMPTED_REG hello
Is this a valid bug? Thanks.
