re PR fortran/83540 (Invalid code with MATMUL, -fno-realloc-lhs -ffrontend-optimize)

2017-12-26  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/83540
	* frontend-passes.c (create_var): If an array to be created
	has unknown size and -fno-realloc-lhs is in effect,
	return NULL.

2017-12-26  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/83540
	* gfortran.dg/inline_matmul_20.f90: New test.

From-SVN: r256003

gcc/fortran/ChangeLog

+2017-12-26  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/83540
+	* frontend-passes.c (create_var): If an array to be created
+	has unknown size and -fno-realloc-lhs is in effect,
+	return NULL.
+
 2017-12-22  Bernhard Reutner-Fischer  <aldot@gcc.gnu.org>
             Eric Botcazou  <ebotcazou@adacore.com>
 

gcc/fortran/frontend-passes.c

@@ -720,6 +720,11 @@ create_var (gfc_expr * e, const char *vname)
   if (e->expr_type == EXPR_CONSTANT || is_fe_temp (e))
     return gfc_copy_expr (e);
 
+  /* Creation of an array of unknown size requires realloc on assignment.
+     If that is not possible, just return NULL.  */
+  if (flag_realloc_lhs == 0 && e->rank > 0 && e->shape == NULL)
+    return NULL;
+
   ns = insert_block ();
 
   if (vname)

gcc/testsuite/ChangeLog

+2017-12-26  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/83540
+	* gfortran.dg/inline_matmul_20.f90: New test.
+
 2017-12-26  Tom de Vries  <tom@codesourcery.com>
 
 	* c-c++-common/unroll-5.c: Use relative line number.

gcc/testsuite/gfortran.dg/inline_matmul_20.f90

+! { dg-do  run }
+! { dg-additional-options "-fno-realloc-lhs -ffrontend-optimize" }
+! This used to segfault at runtime.
+! Original test case by Harald Anlauf.
+program gfcbug142
+  implicit none
+  real, allocatable :: b(:,:)
+  integer :: n = 5
+  character(len=20) :: line
+  allocate (b(n,n))
+  call random_number (b)
+  write (unit=line,fmt='(2I5)') shape (matmul (b, transpose (b)))
+  if (line /= '    5    5') call abort
+end program gfcbug142