On Thu, Jan 01, 2026 at 01:43:50PM -0800, Jerry D wrote:
> On 1/1/26 1:33 PM, Thomas Koenig wrote:
> > > This will avoid potential undefined behavior on various systems. I
> > > will make this change and test. If passes, OK for mainline?
> > 
> > Good thinking.
> > 
> > Your revised version is OK if it passes.
> > 
> > Thanks a lot for the patch!
> > 
> > Best regards
> > 
> >      Thomas
> > 
> 
> Pushed:
> 
> commit 489423763d3c8b84d3409f4b200fb6b19ad96db3 (HEAD -> master,
> origin/master, origin/HEAD)
> Author: Jerry DeLisle <[email protected]>
> Date:   Tue Dec 30 14:46:35 2025 -0800
> 
>     Fortran: Generate a runtime error on recursive I/O
> 
>             PR libfortran/119136

This broke a lot of libgomp tests on all major targets.
Compare e.g.
https://gcc.gnu.org/pipermail/gcc-testresults/2026-January/866363.html
and
https://gcc.gnu.org/pipermail/gcc-testresults/2026-January/866375.html
FAIL: libgomp.fortran/appendix-a/a.2.1.f90   -O3 -fomit-frame-pointer 
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/appendix-a/a.22.8.f90   -O0  execution test
FAIL: libgomp.fortran/appendix-a/a.22.8.f90   -O1  execution test
FAIL: libgomp.fortran/appendix-a/a.22.8.f90   -O2  execution test
FAIL: libgomp.fortran/appendix-a/a.22.8.f90   -O3 -fomit-frame-pointer 
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/appendix-a/a.28.1.f90   -O0  execution test
FAIL: libgomp.fortran/appendix-a/a.28.1.f90   -O2  execution test
FAIL: libgomp.fortran/appendix-a/a.28.1.f90   -O3 -fomit-frame-pointer 
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/appendix-a/a.28.1.f90   -O3 -g  execution test
FAIL: libgomp.fortran/appendix-a/a.28.1.f90   -Os  execution test
FAIL: libgomp.fortran/appendix-a/a.28.2.f90   -O0  execution test
FAIL: libgomp.fortran/appendix-a/a.28.2.f90   -O1  execution test
FAIL: libgomp.fortran/appendix-a/a.28.2.f90   -O2  execution test
FAIL: libgomp.fortran/appendix-a/a.28.2.f90   -O3 -fomit-frame-pointer 
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/appendix-a/a.28.2.f90   -Os  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -O0  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -O1  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -O2  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -O3 -fomit-frame-pointer 
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -O3 -g  execution test
FAIL: libgomp.fortran/appendix-a/a.28.3.f90   -Os  execution test
FAIL: libgomp.fortran/depend-4.f90   -O  execution test
FAIL: libgomp.fortran/omp_hello.f   -O  execution test
FAIL: libgomp.fortran/omp_orphan.f   -O  execution test
FAIL: libgomp.fortran/omp_workshare1.f   -O  execution test
FAIL: libgomp.fortran/omp_workshare2.f   -O  execution test
FAIL: libgomp.fortran/recursion1.f90   -O0  execution test
FAIL: libgomp.fortran/recursion1.f90   -O1  execution test
FAIL: libgomp.fortran/recursion1.f90   -O2  execution test
FAIL: libgomp.fortran/recursion1.f90   -O3 -fomit-frame-pointer -funroll-loops 
-fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/recursion1.f90   -O3 -g  execution test
FAIL: libgomp.fortran/recursion1.f90   -Os  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -O0  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -O1  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -O2  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -O3 -fomit-frame-pointer -funroll-loops 
-fpeel-loops -ftracer -finline-functions  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -O3 -g  execution test
FAIL: libgomp.fortran/rwlock_2.f90   -Os  execution test
all the errors in the logs look like
 1: THREAD#            1 X =            5
 2: THREAD#            0 X =            5
At line 19 of file 
/home/jakub/src/gcc/libgomp/testsuite/libgomp.fortran/appendix-a/a.2.1.f90 
(unit = 6, file = 'stdout')
Fortran runtime error: Recursive I/O not allowed

Error termination. Backtrace:
#0  0xf7e464b0 in data_transfer_init
        at ../../../libgfortran/io/transfer.c:3132
#1  0x8048457 in ???
#2  0xf7a7da32 in gomp_thread_start
        at ../../../libgomp/team.c:129
#3  0xf78a51df in ???
#4  0xf792b2d7 in ???
#5  0xffffffff in ???

Recursive I/O shouldn't indeed be allowed, but multiple threads
trying to transfer concurrently should be fine (of course, locking
should be used for that).

        Jakub

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