re PR fortran/31203 ([4.1/4.2 only] Character length should never be negative)

	PR fortran/31203

	* trans-expr.c (gfc_trans_init_string_length): Length should
	never be negative.
	(gfc_conv_function_call): Likewise.

	* gfortran.dg/string_length_1.f90: New test.

From-SVN: r123051

gcc/fortran/ChangeLog

+2007-03-19  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
+	PR fortran/31203
+	* trans-expr.c (gfc_trans_init_string_length): Length should
+	never be negative.
+	(gfc_conv_function_call): Likewise.
+
 2007-03-18  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/30531

gcc/fortran/trans-expr.c

@@ -227,6 +227,8 @@ gfc_trans_init_string_length (gfc_charlen * cl, stmtblock_t * pblock)
 
   gfc_init_se (&se, NULL);
   gfc_conv_expr_type (&se, cl->length, gfc_charlen_type_node);
+  se.expr = fold_build2 (MAX_EXPR, gfc_charlen_type_node, se.expr,
+			 build_int_cst (gfc_charlen_type_node, 0));
   gfc_add_block_to_block (pblock, &se.pre);
 
   tmp = cl->backend_decl;
@@ -2256,6 +2258,8 @@ gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
         }
         else
         {
+	  tree tmp;
+
 	  /* Calculate the length of the returned string.  */
 	  gfc_init_se (&parmse, NULL);
 	  if (need_interface_mapping)
@@ -2264,7 +2268,11 @@ gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
 	    gfc_conv_expr (&parmse, sym->ts.cl->length);
 	  gfc_add_block_to_block (&se->pre, &parmse.pre);
 	  gfc_add_block_to_block (&se->post, &parmse.post);
-	  cl.backend_decl = fold_convert (gfc_charlen_type_node, parmse.expr);
+	  
+	  tmp = fold_convert (gfc_charlen_type_node, parmse.expr);
+	  tmp = fold_build2 (MAX_EXPR, gfc_charlen_type_node, tmp,
+			     build_int_cst (gfc_charlen_type_node, 0));
+	  cl.backend_decl = tmp;
 	}
 
       /* Set up a charlen structure for it.  */

gcc/testsuite/ChangeLog

+2007-03-19  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
+	PR fortran/31203
+	* gfortran.dg/string_length_1.f90: New test.
+
 2007-03-18  John David Anglin  <dave.anglin@nrc-cnrc.gc.ca>
 
 	PR testsuite/30395

gcc/testsuite/gfortran.dg/string_length_1.f90

+! { dg-do run }
+! Testcase for PR 31203
+! We used to create strings with negative length
+subroutine foo(i)
+  integer :: i
+  character(len=i) :: s(2)
+  if (len(s) < 0) call abort
+  if (len(s) /= max(i,0)) call abort
+end
+
+function gee(i)
+  integer, intent(in) :: i
+  character(len=i) :: gee
+
+  gee = ""
+end function gee
+
+subroutine s1(i,j)
+  character(len=i-j) :: a
+  if (len(a) < 0) call abort()
+end subroutine
+
+program test
+  interface
+    function gee(i)
+      integer, intent(in) :: i
+      character(len=i) :: gee
+    end function gee
+  end interface
+
+  call foo(2)
+  call foo(-1)
+  call s1(1,2)
+  call s1(-1,-8)
+  call s1(-8,-1)
+
+  if (len(gee(2)) /= 2) call abort
+  if (len(gee(-5)) /= 0) call abort
+  if (len(gee(intfunc(3))) /= max(intfunc(3),0)) call abort
+  if (len(gee(intfunc(2))) /= max(intfunc(2),0)) call abort
+
+  if (len(bar(2)) /= 2) call abort
+  if (len(bar(-5)) /= 0) call abort
+  if (len(bar(intfunc(3))) /= max(intfunc(3),0)) call abort
+  if (len(bar(intfunc(2))) /= max(intfunc(2),0)) call abort
+
+  if (cow(bar(2)) /= 2) call abort
+  if (cow(bar(-5)) /= 0) call abort
+  if (cow(bar(intfunc(3))) /= max(intfunc(3),0)) call abort
+  if (cow(bar(intfunc(2))) /= max(intfunc(2),0)) call abort
+
+contains
+
+  function bar(i)
+    integer, intent(in) :: i
+    character(len=i) :: bar
+  
+    bar = ""
+  end function bar
+
+  function cow(c)
+    character(len=*), intent(in) :: c
+    integer :: cow
+    cow = len(c)
+  end function cow
+
+  pure function intfunc(i)
+    integer, intent(in) :: i
+    integer :: intfunc
+
+    intfunc = 2*i-5
+  end function intfunc
+
+end program test