[PATCH] PR fortran/85796 - Floating point exception with implied do

[PATCH] PR fortran/85796 - Floating point exception with implied do

[Harald Anlauf]

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The patch below is based on a previous version by Steve.
The present version fixes an additional copy&paste error.

Needless to say that it (still!) regtests cleanly on x86_64-pc-linux-gnu.

OK for master?  As it appears safe, OK for backport to at least 10-branch?

Thanks,
Harald


PR fortran/85796 - Floating point exception with implied do

Catch invalid step=0 in implied do loop within data statements.

gcc/fortran/ChangeLog:

	PR fortran/85796
	* resolve.c (traverse_data_list): Fix copy&paste errors; catch
	step=0 in implied do loop.

gcc/testsuite/ChangeLog:

	PR fortran/85796
	* gfortran.dg/pr85796.f90: New test.


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diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 1641eb6ca10..b6d21ad1bac 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -16327,7 +16327,7 @@ traverse_data_list (gfc_data_variable *var, locus *where)
       || end->expr_type != EXPR_CONSTANT)
     {
       gfc_error ("end of implied-do loop at %L could not be "
-		 "simplified to a constant value", &start->where);
+		 "simplified to a constant value", &end->where);
       retval = false;
       goto cleanup;
     }
@@ -16335,7 +16335,14 @@ traverse_data_list (gfc_data_variable *var, locus *where)
       || step->expr_type != EXPR_CONSTANT)
     {
       gfc_error ("step of implied-do loop at %L could not be "
-		 "simplified to a constant value", &start->where);
+		 "simplified to a constant value", &step->where);
+      retval = false;
+      goto cleanup;
+    }
+  if (mpz_cmp_si (step->value.integer, 0) == 0)
+    {
+      gfc_error ("step of implied-do loop at %L shall not be zero",
+		 &step->where);
       retval = false;
       goto cleanup;
     }
diff --git a/gcc/testsuite/gfortran.dg/pr85796.f90 b/gcc/testsuite/gfortran.dg/pr85796.f90
new file mode 100644
index 00000000000..78683787fbb
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr85796.f90
@@ -0,0 +1,8 @@
+! { dg-do compile }
+! PR fortran/85796 - Floating point exception with implied do in data statement
+
+program p
+  implicit none
+  integer :: i, j, x(2,2)
+  data ((x(i,j),i=1,2,j-1),j=1,2) /3*789/ ! { dg-error "step of implied-do loop" }
+end

Re: [PATCH] PR fortran/85796 - Floating point exception with implied do

[Tobias Burnus]

On 23.11.20 22:18, Harald Anlauf wrote:

> The patch below is based on a previous version by Steve.
> The present version fixes an additional copy&paste error.
>
> Needless to say that it (still!) regtests cleanly on x86_64-pc-linux-gnu.
>
> OK for master?  As it appears safe, OK for backport to at least 10-branch?

LGTM. Thanks for the patch; I think we can backport it to GCC 10.

Tobias

PS: Sorry for the slow patch review

> PR fortran/85796 - Floating point exception with implied do
>
> Catch invalid step=0 in implied do loop within data statements.
>
> gcc/fortran/ChangeLog:
>
>       PR fortran/85796
>       * resolve.c (traverse_data_list): Fix copy&paste errors; catch
>       step=0 in implied do loop.
>
> gcc/testsuite/ChangeLog:
>
>       PR fortran/85796
>       * gfortran.dg/pr85796.f90: New test.
>
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