[patch, fortran] Fix PR 68009, wrong prototype in runtime_error

[Thomas Koenig <tkoenig at netcologne dot de>]

Hello world,

this fixes a 7/8/9 regression. The problem is that front-end inlining
of matmul could generate calls to _gfortran_runtime_error which were
called as non-variadic.  This fixes the problem by setting the
backend_decl on the resovled symbol, so it always uses the right one.

Putting it into the resolution stage seems a bit strange, but I tried
several other methods such as putting it into the global symbol table,
and nothing else I tried worked.

You can check on x86_64 if the patch works by doing

$ cat nn.f90
module x
contains
  subroutine mm(a,b,c)
    real, dimension(:) :: a, c
    real, dimension(:,:) :: b
    c = matmul(a,b)
  end subroutine mm
end module x

$ gfortran -S -O -fcheck=bounds nn.f90

and then looking for code snippets like

        movl    $89, %ecx
        movq    %rdi, %rdx
        movl    $.LC0, %edi
        movl    $0, %eax
        call    _gfortran_runtime_error

where setting %eax to zero indicates that we are indeed using
varargs, because %eax contains the number of float arguments,
which is zero.

No test case, because there is not really a good way to check for this.

So, OK for trunk?

Regards

	Thomas

2019-03-17  Thomas Koenig  <tkoeng@gcc.gnu.org>

	PR fortran/68009
	* iresolve.c: Include trans.h.
	(gfc_resolve_fe_runtine_error): Set backend_decl on
	resolved_sym.

Index: iresolve.c
===================================================================
--- iresolve.c	(Revision 269624)
+++ iresolve.c	(Arbeitskopie)
@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "intrinsic.h"
 #include "constructor.h"
 #include "arith.h"
+#include "trans.h"
 
 /* Given printf-like arguments, return a stable version of the result string.
 
@@ -2495,6 +2496,10 @@ gfc_resolve_fe_runtime_error (gfc_code *c)
     a->name = "%VAL";
 
   c->resolved_sym = gfc_get_intrinsic_sub_symbol (name);
+  /* We set the backend_decl here because runtime_error is a
+     variadic function and we would use the wrong calling
+     convention otherwise.  */
+  c->resolved_sym->backend_decl = gfor_fndecl_runtime_error;
 }
 
 void