Re: [PATCH 5/5] lto: Support #pragma GCC diagnostic [PR80922] [PR106823] [PR107936]

[Torbjorn SVENSSON]

On 2026-08-05 02:06, Lewis Hyatt wrote:

On Tue, Aug 04, 2026 at 02:31:51PM +0200, Torbjorn SVENSSON wrote:

Hello,

The new gcc.dg/lto/pr80922 test appears to fail for all arm-none-eabi targets:

Testing gcc.dg/lto/pr80922-2, -O0 -flto -flto-partition=none -fuse-linker-plugin
doing compile
Executing on host: /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc   
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto   
-fdiagnostics-plain-output  -O0 -flto -flto-partition=none -fuse-linker-plugin  
-O2 -Wfree-nonheap-object -c     -o c_lto_pr80922-2_0.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_0.c    (timeout = 800)
spawn -ignore SIGHUP /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc 
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto 
-fdiagnostics-plain-output -O0 -flto -flto-partition=none -fuse-linker-plugin 
-O2 -Wfree-nonheap-object -c -o c_lto_pr80922-2_0.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_0.c
pid is 703324 -703324
pid is -1
output is  status 0
PASS: gcc.dg/lto/pr80922-2 c_lto_pr80922-2_0.o assemble, -O0 -flto 
-flto-partition=none -fuse-linker-plugin
doing compile
Executing on host: /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc   
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto   
-fdiagnostics-plain-output  -O0 -flto -flto-partition=none -fuse-linker-plugin  
-O2 -Wfree-nonheap-object -c     -o c_lto_pr80922-2_1.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c    (timeout = 800)
spawn -ignore SIGHUP /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc 
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto 
-fdiagnostics-plain-output -O0 -flto -flto-partition=none -fuse-linker-plugin 
-O2 -Wfree-nonheap-object -c -o c_lto_pr80922-2_1.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c
pid is 703370 -703370
pid is -1
output is  status 0
PASS: gcc.dg/lto/pr80922-2 c_lto_pr80922-2_1.o assemble, -O0 -flto 
-flto-partition=none -fuse-linker-plugin
doing compile
Executing on host: /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc   
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto   
-fdiagnostics-plain-output  -O0 -flto -flto-partition=none -fuse-linker-plugin  
-O2 -Wfree-nonheap-object -c     -o c_lto_pr80922-2_2.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_2.c    (timeout = 800)
spawn -ignore SIGHUP /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc 
-mthumb -march=armv6s-m -mcpu=cortex-m0 -mfloat-abi=soft -mfpu=auto 
-fdiagnostics-plain-output -O0 -flto -flto-partition=none -fuse-linker-plugin 
-O2 -Wfree-nonheap-object -c -o c_lto_pr80922-2_2.o 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_2.c
pid is 703406 -703406
pid is -1
output is  status 0
PASS: gcc.dg/lto/pr80922-2 c_lto_pr80922-2_2.o assemble, -O0 -flto 
-flto-partition=none -fuse-linker-plugin
doing compile
Executing on host: /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc  
c_lto_pr80922-2_1.o c_lto_pr80922-2_2.o  -mthumb -march=armv6s-m -mcpu=cortex-m0 
-mfloat-abi=soft -mfpu=auto   -dumpbase "" -fdiagnostics-plain-output  -r       
--specs=rdimon.specs -Wl,--start-group -lc -lm -Wl,--end-group --specs=nosys.specs 
-Wl,--allow-multiple-definition -Wl,-u,_isatty,-u,_fstat  -Wl,-wrap,exit -Wl,-wrap,_exit 
-Wl,-wrap,main -Wl,-wrap,abort -Wl,gcc_tg.o    -o c_lto_pr80922-2.o    (timeout = 800)
spawn -ignore SIGHUP /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc 
c_lto_pr80922-2_1.o c_lto_pr80922-2_2.o -mthumb -march=armv6s-m -mcpu=cortex-m0 
-mfloat-abi=soft -mfpu=auto -dumpbase  -fdiagnostics-plain-output -r 
--specs=rdimon.specs -Wl,--start-group -lc -lm -Wl,--end-group 
--specs=nosys.specs -Wl,--allow-multiple-definition -Wl,-u,_isatty,-u,_fstat 
-Wl,-wrap,exit -Wl,-wrap,_exit -Wl,-wrap,main -Wl,-wrap,abort -Wl,gcc_tg.o -o 
c_lto_pr80922-2.o
pid is 703440 -703440
/build/r17-2833-g32657f29f91871/arm-none-eabi/bin/ld: warning: incremental 
linking of LTO and non-LTO objects; using -flinker-output=nolto-rel which will 
bypass whole program optimization
In function 'myfree2',
     inlined from 'main' at 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:8:3:
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c:5:3: warning: 
'__builtin_free' called on unallocated object 'a' [-Wfree-nonheap-object]
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c: In function 'main':
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:4:13: note: declared here
In function 'myfree2',
     inlined from 'main' at 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:8:3:
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c:10:3: warning: 
'__builtin_free' called on unallocated object 'c' [-Wfree-nonheap-object]
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c: In function 'main':
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:4:19: note: declared here
pid is -1
output is /build/r17-2833-g32657f29f91871/arm-none-eabi/bin/ld: warning: 
incremental linking of LTO and non-LTO objects; using -flinker-output=nolto-rel 
which will bypass whole program optimization
In function 'myfree2',
     inlined from 'main' at 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:8:3:
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c:5:3: warning: 
'__builtin_free' called on unallocated object 'a' [-Wfree-nonheap-object]
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c: In function 'main':
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:4:13: note: declared here
In function 'myfree2',
     inlined from 'main' at 
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:8:3:
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-2_1.c:10:3: warning: 
'__builtin_free' called on unallocated object 'c' [-Wfree-nonheap-object]
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c: In function 'main':
/build/gcc_src/gcc/testsuite/gcc.dg/lto/pr80922-1_1.c:4:19: note: declared here
  status 0
FAIL: gcc.dg/lto/pr80922-2 c_lto_pr80922-2_2.o-c_lto_pr80922-2_2.o link, 
incr-link
doing compile
Executing on host: /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc  
c_lto_pr80922-2_0.o c_lto_pr80922-2.o  -mthumb -march=armv6s-m -mcpu=cortex-m0 
-mfloat-abi=soft -mfpu=auto   -dumpbase "" -fdiagnostics-plain-output  -O0 
-flto -flto-partition=none -fuse-linker-plugin -O2 -Wfree-nonheap-object       
--specs=rdimon.specs -Wl,--start-group -lc -lm -Wl,--end-group --specs=nosys.specs 
-Wl,--allow-multiple-definition -Wl,-u,_isatty,-u,_fstat  -Wl,-wrap,exit -Wl,-wrap,_exit 
-Wl,-wrap,main -Wl,-wrap,abort -Wl,gcc_tg.o   -T qemu.ld -o gcc-dg-lto-pr80922-2-01.exe   
 (timeout = 800)
spawn -ignore SIGHUP /build/r17-2833-g32657f29f91871/bin/arm-none-eabi-gcc 
c_lto_pr80922-2_0.o c_lto_pr80922-2.o -mthumb -march=armv6s-m -mcpu=cortex-m0 
-mfloat-abi=soft -mfpu=auto -dumpbase  -fdiagnostics-plain-output -O0 -flto 
-flto-partition=none -fuse-linker-plugin -O2 -Wfree-nonheap-object 
--specs=rdimon.specs -Wl,--start-group -lc -lm -Wl,--end-group 
--specs=nosys.specs -Wl,--allow-multiple-definition -Wl,-u,_isatty,-u,_fstat 
-Wl,-wrap,exit -Wl,-wrap,_exit -Wl,-wrap,main -Wl,-wrap,abort -Wl,gcc_tg.o -T 
qemu.ld -o gcc-dg-lto-pr80922-2-01.exe
pid is 703533 -703533
pid is -1
output is  status 0
FAIL: gcc.dg/lto/pr80922-2  (test for LTO warnings, pr80922-2_0.c line 10 -O0 
-flto -flto-partition=none -fuse-linker-plugin)
FAIL: gcc.dg/lto/pr80922-2  (test for LTO warnings, pr80922-2_0.c line 15 -O0 
-flto -flto-partition=none -fuse-linker-plugin)
FAIL: gcc.dg/lto/pr80922-2  (test for LTO warnings, pr80922-2_1.c line 5 -O0 
-flto -flto-partition=none -fuse-linker-plugin)
FAIL: gcc.dg/lto/pr80922-2  (test for LTO warnings, pr80922-2_1.c line 10 -O0 
-flto -flto-partition=none -fuse-linker-plugin)
PASS: gcc.dg/lto/pr80922-2 c_lto_pr80922-2_0.o-c_lto_pr80922-2.o link, -O0 
-flto -flto-partition=none -fuse-linker-plugin


Kind regards,
Torbjörn

Thanks, so the test is expecting an LTO-only partial link, and it gets
tripped up because this target adds an extra non-LTO wrapper object to every
link. The attached patch disables the test using
check_effective_target_unwrapped, which I think is the way to go for now? It
works fine on x86-64, fwiw, in that the incr-link test still runs as
before. I don't think I have a way to test on arm-none-eabi myself, unless
there is a cfarm machine I have not found for that...

I've tested below patch on top of r17-2833-g32657f29f91871 and it appears to do 
the job. I do, however, not know if there is any better solution than disabling 
the incr-link.
What impact do you think it would have to compile the testglue.c from dejagnu 
with -flto? Would that be a better solution?
If think it's possible to add -flto when building testglue.c by adding

set_board_info wrap_compile_flags "-flto"

to the board definition. Perhaps, this is something that the harness in GCC 
should do?

Kind regards,
Torbjörn

-Lewis


0001-lto-testsuite-Skip-incr-link-tests-on-targets-with-wra.txt

[PATCH] lto: testsuite: Skip incr-link tests on targets with wrapper object 
[PR80922]

The new incr-link LTO test expects to perform an LTO incremental link, but
targets making use of a wrapper object add a non-LTO object to the link, in
which case the test needs to be skipped.

gcc/testsuite/ChangeLog:

        PR middle-end/80922
        * lib/lto.exp: Skip incremental linking test for wrapped targets.
---
  gcc/testsuite/lib/lto.exp | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/lib/lto.exp b/gcc/testsuite/lib/lto.exp
index 7243547a52d..db19ff00855 100644
--- a/gcc/testsuite/lib/lto.exp
+++ b/gcc/testsuite/lib/lto.exp
@@ -854,7 +854,9 @@ proc lto-execute-1 { src1 sid } {
        # Only attempt the incr-link mode if the linker plugin is explicitly in 
use.
        set sav_compile_type $compile_type
        set sav_obj_list $obj_list
-       if { $is_incr_link && [lsearch -exact $option "-fuse-linker-plugin"] < 
0 } {
+       if { $is_incr_link
+            && ([lsearch -exact $option "-fuse-linker-plugin"] < 0
+                || ![check_effective_target_unwrapped]) } {
            set compile_type "link"
        } elseif { $is_incr_link || $is_ar_link } {
            set mainsrc [lindex $obj_list 0]