[PATCH] Bail out in gfc_dep_compare_expr for a NULL argument.

[Martin Liška]

Hi.

The patch is about early bail out in gfc_dep_compare_expr function
when one of the arguments (and not both at the same time) is null.
I'm not sure, it's a proper fix however.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

gcc/fortran/ChangeLog:

2019-12-10  Martin Liska  <mli...@suse.cz>

        PR fortran/92874
        * dependency.c (gfc_dep_compare_expr): Bail out
        when one of the arguments is null.

gcc/testsuite/ChangeLog:

2019-12-10  Martin Liska  <mli...@suse.cz>

        PR fortran/92874
        * gfortran.dg/pr92874.f90: New test.
---
 gcc/fortran/dependency.c              |  2 ++
 gcc/testsuite/gfortran.dg/pr92874.f90 | 11 +++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 gcc/testsuite/gfortran.dg/pr92874.f90



diff --git a/gcc/fortran/dependency.c b/gcc/fortran/dependency.c
index 394d85b48a2..eb741137d60 100644
--- a/gcc/fortran/dependency.c
+++ b/gcc/fortran/dependency.c
@@ -319,6 +319,8 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 
   if (e1 == NULL && e2 == NULL)
     return 0;
+  else if (e1 == NULL || e2 == NULL)
+    return -2;
 
   e1 = gfc_discard_nops (e1);
   e2 = gfc_discard_nops (e2);
diff --git a/gcc/testsuite/gfortran.dg/pr92874.f90 b/gcc/testsuite/gfortran.dg/pr92874.f90
new file mode 100644
index 00000000000..a1fca3d7718
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr92874.f90
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! { dg-options "-O2" }
+! PR fortran/92874
+program p
+   call s('a')
+   call s('abc')
+end
+subroutine s(x)
+   character(*) :: x
+   print *, (x(1:1) == x(1:))
+end