[Bug c/84619] New: Segmentation fault when running a c-program which is calling a fortran subroutine

[mario-baumann at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84619

            Bug ID: 84619
           Summary: Segmentation fault when running a c-program which is
                    calling a fortran subroutine
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mario-baumann at web dot de
  Target Milestone: ---

Created attachment 43531
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43531&action=edit
contains the 4 sources: lnx_c.c, lnx_f.f, mac_c.c and mac_f.f

I have a strange segmentation fault when running the c-programm which is
calling a fortran subroutine.

The strip down created slightly different codes on linux and macOS.

GCC revision: 258059

Tested on:
(1) linux
> /Gcc/8.0.1/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/Gcc/8.0.1/bin/gcc
COLLECT_LTO_WRAPPER=/opt/Gcc/8.0.1/bin/../libexec/gcc/x86_64-pc-linux-gnu/8.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /Gcc/8.0.1/.src/configure --prefix=/Gcc/8.0.1
--enable-languages=c,c++,fortran --enable-lto --disable-nls
--disable-libquadmath --disable-libquadmath-support
Thread model: posix
gcc version 8.0.1 20180228 (experimental) (GCC) 

> /Gcc/8.0.1/bin/gcc -c -m64 -march=nocona -O1 lnx_c.c
> /Gcc/8.0.1/bin/gfortran -o z_lnx -m64 -march=nocona lnx_c.o lnx_f.f
> ./z_lnx 
Segmentation fault (core dumped)


(2) macOS
> /Gcc/8.0.1/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/Gcc/8.0.1/bin/gcc
COLLECT_LTO_WRAPPER=/Gcc/8.0.1/libexec/gcc/x86_64-apple-darwin17/8.0.1/lto-wrapper
Target: x86_64-apple-darwin17
Configured with: /Gcc/8.0.1/.src/configure --prefix=/Gcc/8.0.1
--build=x86_64-apple-darwin17 --enable-languages=c,c++,fortran --enable-lto
--enable-stage1-checking --enable-libstdcxx-time --disable-nls
--disable-libquadmath --disable-libquadmath-support --with-ld=/opt/local/bin/ld
--with-ar=/opt/local/bin/ar --with-as=/opt/local/bin/as --with-system-zlib
--with-pkgversion=svn-revision-258059
Thread model: posix
gcc version 8.0.1 20180228 (experimental) (svn-revision-258059)

> /Gcc/8.0.1/bin/gcc -c -m64 -march=nocona -O1 mac_c.c
> /Gcc/8.0.1/bin/gfortran -o z_mac -m64 -march=nocona mac_c.o mac_f.f
> ./z_mac
Segmentation fault: 11



Findings:
(1) -O2 instead of -O1 crashes too
(2) -O0 works fiine
(3) gcc-7.3 works fine with -O0, -O1 and -O2
(4) valgrind complains about:
==11458==    at 0x501846A: _gfortran_string_index (string_intrinsics_inc.c:254)
==11458==    at 0x5018483: _gfortran_string_index (string_intrinsics_inc.c:270)