https://gcc.gnu.org/g:d25728c98682c058bfda79333c94b0a8cf2a3f49
commit r15-9210-gd25728c98682c058bfda79333c94b0a8cf2a3f49
Author: Jakub Jelinek <ja...@redhat.com>
Date: Fri Apr 4 20:57:09 2025 +0200
lto: lto-opts fixes [PR119625]
I can reproduce a really weird error in our distro i686 trunk gcc
(but haven't managed to reproduce it with vanilla trunk yet).
echo 'void foo (void) {}' > a.c; gcc -O2 -flto=auto -m32 -march=i686
-ffat-lto-objects -fhardened -o a.o -c a.c; gcc -O2 -flto=auto -m32 -march=i686
-r -o a.lo a.o
lto1: fatal error: open failed: No such file or directory
compilation terminated.
lto-wrapper: fatal error: gcc returned 1 exit status
The error is because
cat ./a.lo.lto.o-args.0
""
a.o
My suspicion is that this "" in there is caused by weird .gnu.lto_.opts
section content during
gcc -O2 -flto=auto -m32 -march=i686 -ffat-lto-objects -fhardened -S -o a.s
-c a.c
compilation (and I can reproduce that one with vanilla trunk).
The above results in
.section .gnu.lto_.opts,"e",@progbits
.string "'-fno-openmp' '-fno-openacc' '-fPIC' '' '-m32'
'-march=i686' '-O2' '-flto=auto' '-ffat-lto-objects'"
There are two weird things, one (IMHO the cause of the "" later on) is
the '' part, I think it comes from lto_write_options doing
append_to_collect_gcc_options (&temporary_obstack, &first_p, "");
IMHO it shouldn't call append_to_collect_gcc_options at all for that case.
The -fhardened option causes global_options.x_flag_cf_protection
to be set to CF_FULL and later on the backend option processing
sets it to CF_FULL | CF_SET (i.e. 7, a value not handled in
lto_write_options).
The following patch fixes it by not emitting anything there if
flag_cf_protection is one of the unhandled values.
Perhaps it could incrementally use
switch (global_options.x_flag_cf_protection & ~CF_SET)
instead, dunno.
And the other problem is that the -fPIC in there is really weird.
Our distro compiler or vanilla configured trunk certainly doesn't
default to -fPIC and -fhardened uses -fPIE when
-fPIC/-fpic/-fno-pie/-fno-pic is not specified, so I was expecting
-fPIE in there.
The thing is that the -fpie option causes setting of both
global_options.x_flag_pi{c,e} to 1, -fPIE both to 2:
/* If -fPIE or -fpie is used, turn on PIC. */
if (opts->x_flag_pie)
opts->x_flag_pic = opts->x_flag_pie;
else if (opts->x_flag_pic == -1)
opts->x_flag_pic = 0;
if (opts->x_flag_pic && !opts->x_flag_pie)
opts->x_flag_shlib = 1;
so checking first for flag_pic == 2 and then flag_pic == 1
and only afterwards for flag_pie means we never print
-fPIE/-fpie.
Or do you want something further (like
switch (global_options.x_flag_cf_protection & ~CF_SET)
)?
2025-04-04 Jakub Jelinek <ja...@redhat.com>
PR lto/119625
* lto-opts.cc (lto_write_options): If neither flag_pic nor
flag_pie are set, check first for flag_pie and only later
for flag_pic rather than the other way around, use a temporary
variable. If flag_cf_protection is not set, don't append anything
if flag_cf_protection is none of CF_{NONE,FULL,BRANCH,RETURN} and
use a temporary variable.
Diff:
---
gcc/lto-opts.cc | 43 ++++++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 21 deletions(-)
diff --git a/gcc/lto-opts.cc b/gcc/lto-opts.cc
index dee1caafc558..3959598b497c 100644
--- a/gcc/lto-opts.cc
+++ b/gcc/lto-opts.cc
@@ -82,31 +82,32 @@ lto_write_options (void)
subject of merging in lto-wrapper. */
if (!OPTION_SET_P (flag_pic) && !OPTION_SET_P (flag_pie))
{
- append_to_collect_gcc_options (&temporary_obstack, &first_p,
- global_options.x_flag_pic == 2
- ? "-fPIC"
- : global_options.x_flag_pic == 1
- ? "-fpic"
- : global_options.x_flag_pie == 2
- ? "-fPIE"
- : global_options.x_flag_pie == 1
- ? "-fpie"
- : "-fno-pie");
+ const char *pic = "-fno-pie";
+ if (global_options.x_flag_pie == 2)
+ pic = "-fPIE";
+ else if (global_options.x_flag_pie == 1)
+ pic = "-fpie";
+ else if (global_options.x_flag_pic == 2)
+ pic = "-fPIC";
+ else if (global_options.x_flag_pic == 1)
+ pic = "-fpic";
+ append_to_collect_gcc_options (&temporary_obstack, &first_p, pic);
}
if (!OPTION_SET_P (flag_cf_protection))
{
- append_to_collect_gcc_options (
- &temporary_obstack, &first_p,
- global_options.x_flag_cf_protection == CF_NONE
- ? "-fcf-protection=none"
- : global_options.x_flag_cf_protection == CF_FULL
- ? "-fcf-protection=full"
- : global_options.x_flag_cf_protection == CF_BRANCH
- ? "-fcf-protection=branch"
- : global_options.x_flag_cf_protection == CF_RETURN
- ? "-fcf-protection=return"
- : "");
+ const char *cf_protection = NULL;
+ switch (global_options.x_flag_cf_protection)
+ {
+ case CF_NONE: cf_protection = "-fcf-protection=none"; break;
+ case CF_FULL: cf_protection = "-fcf-protection=full"; break;
+ case CF_BRANCH: cf_protection = "-fcf-protection=branch"; break;
+ case CF_RETURN: cf_protection = "-fcf-protection=return"; break;
+ default: break;
+ }
+ if (cf_protection)
+ append_to_collect_gcc_options (&temporary_obstack, &first_p,
+ cf_protection);
}
/* If debug info is enabled append -g. */
