[Bug fortran/70040] [6 Regression] ICE in gimplify.c with deferred-length strings

["tkoenig at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pault at gcc dot gnu.org

--- Comment #6 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
I've been giving this a look, and I have not been able
(in the time that I can currently spend on this) to
get rid of the gimplification error.

There are two possibilities:

a) Revert r233797.  I'd hate to do this, because it removes
(IMHO) a major piece of usability.

b) Fix things some other way.  One possibility would be to still do
the analysis in the front-end pass and mark the expression as needing
a string temporary, with something like this:

Index: frontend-passes.c
===================================================================
--- frontend-passes.c   (Revision 233797)
+++ frontend-passes.c   (Arbeitskopie)
@@ -158,7 +158,6 @@ realloc_string_callback (gfc_code **c, int *walk_s
 {
   gfc_expr *expr1, *expr2;
   gfc_code *co = *c;
-  gfc_expr *n;

   if (co->op != EXEC_ASSIGN)
     return 0;
@@ -174,10 +173,9 @@ realloc_string_callback (gfc_code **c, int *walk_s

   if (!gfc_check_dependency (expr1, expr2, true))
     return 0;
-  
-  current_code = c;
-  n = create_var (expr2, "trim");
-  co->expr2 = n;
+
+  co->expr2->needs_string_temp = 1;
+
   return 0;
 }

Index: gfortran.h
===================================================================
--- gfortran.h  (Revision 233587)
+++ gfortran.h  (Arbeitskopie)
@@ -2020,6 +2020,9 @@ typedef struct gfc_expr
   /* Will require finalization after use.  */
   unsigned int must_finalize : 1;

+  /* This needs a string temporary.  */
+  unsigned int needs_string_temp;
+
   /* If an expression comes from a Hollerith constant or compile-time
      evaluation of a transfer statement, it may have a prescribed target-
      memory representation, and these cannot always be backformed from

... and then handle the string generation in gfc_conv_substring_expr.

Problem is, I don't really know how to do the second part.  I can try
to copy some code from gfc_conv_concat_op, but I have never been
comfortable with this part of the compiler.

Paul, maybe you could help?