[patch, fortran, committed] Fix PR 85641

[patch, fortran, committed] Fix PR 85641

[Thomas Koenig]

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Hello world,

I have just committed the attached patch as obvious after
regression-testing.

Since this fixes a regression, I will backport to gcc8 and gcc7 in
the next days.

Regards

	Thomas

2018-06-06  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/85641
	* frontend-passes.c (is_fe_temp): Add prototype.
	(realloc_string_callback): Early return for frontend-generated
	temporary.

2018-06-06  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/85641
	* gfortran.dg/realloc_on_assign_30.f90: New test.


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Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 261245)
+++ frontend-passes.c	(Arbeitskopie)
@@ -57,6 +57,8 @@ static bool has_dimen_vector_ref (gfc_expr *);
 static int matmul_temp_args (gfc_code **, int *,void *data);
 static int index_interchange (gfc_code **, int*, void *);
 
+static bool is_fe_temp (gfc_expr *e);
+
 #ifdef CHECKING_P
 static void check_locus (gfc_namespace *);
 #endif
@@ -254,6 +256,9 @@ realloc_string_callback (gfc_code **c, int *walk_s
       || !expr1->ts.deferred)
     return 0;
 
+  if (is_fe_temp (expr1))
+    return 0;
+
   expr2 = gfc_discard_nops (co->expr2);
 
   if (expr2->expr_type == EXPR_VARIABLE)

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! { dg-do compile }
! PR 85641 - this used to ICE due do infinite recursion.
! Test case by Antony Lewis.
program tester
character(LEN=:), allocatable :: fields
integer j
character(LEN=4), parameter :: CMB_CL_Fields = 'TEBP'

fields = ''
j=1
fields = fields // CMB_CL_Fields(j:j)

end program tester