https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93762

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-04-10
                 CC|                            |tkoenig at gcc dot gnu.org

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Unfortunately, the test case fails with different ways on
current trunk:

$ gfortran -g  a.f90
$ ./a.out
 at bot of deepest_call, str is "12345"

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0  0x7f0a66c3059f in ???
        at
/usr/src/debug/glibc-2.26-lp151.19.11.1.x86_64/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
#1  0x400c65 in __interface_call_m_MOD_interface_call
        at /tmp/a.f90:20
#2  0x400d99 in MAIN__
        at /tmp/a.f90:32
#3  0x400f0b in main
        at /tmp/a.f90:25
Speicherzugriffsfehler (Speicherabzug geschrieben)

(gdb) r a.f90 
Starting program: /tmp/a.out a.f90
 at bot of deepest_call, str is "12345"

Program received signal SIGSEGV, Segmentation fault.
_gfortran_string_len_trim (s=0x6068d0 "12345", len=<optimized out>) at
../../../gcc/libgfortran/intrinsics/string_intrinsics_inc.c:231
231               if (*((unsigned long*) (s + i + 1)) != blank_longword)
(gdb) p s
$1 = 0x6068d0 "12345"
(gdb) p i
$2 = 564082115390472183

Seems like uninitialzed memory for i.

Valgrind confirms this:

$ valgrind ./a.out
==5621== Memcheck, a memory error detector
==5621== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==5621== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==5621== Command: ./a.out
==5621== 
 at bot of deepest_call, str is "12345"
==5621== Conditional jump or move depends on uninitialised value(s)
==5621==    at 0x50A29A5: _gfortran_string_len_trim
(string_intrinsics_inc.c:188)
==5621==    by 0x50A2A87: _gfortran_string_trim (string_intrinsics_inc.c:168)
==5621==    by 0x400C65: __interface_call_m_MOD_interface_call (a.f90:20)
==5621==    by 0x400D99: MAIN__ (a.f90:32)
==5621==    by 0x400F0B: main (a.f90:25)

Not sure if this ever worked in a released version.

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