[PATCH] Fix PR47839

[Richard Guenther]

This avoids putting extern decls with NULL DECL_CONTEXT into the
BLOCK tree, which is bogus and confuses LTO and dwarf2out.  The
proper way to bring externs into scope is to insert a decl copy
with function DECL_CONTEXT into the BLOCKs (into every relevant
block, not just the first as done by the FE).

Bootstrapped and tested on x86_64-unknown-linux-gnu, I also built
SPEC with -flto and debug-info to verify this ICE is fixed.

Ok?

Thanks,
Richard.

2011-02-23  Richard Guenther  <rguenther@suse.de>

	PR fortran/47839
	* f95-lang.c (pushdecl): For externs in non-global scope push
	a copy of the decl into the BLOCK.

	* gfortran.dg/lto/pr47839_0.f90: New testcase.
	* gfortran.dg/lto/pr47839_1.f90: Likewise.

Index: gcc/fortran/f95-lang.c
===================================================================
*** gcc/fortran/f95-lang.c	(revision 170407)
--- gcc/fortran/f95-lang.c	(working copy)
*************** poplevel (int keep, int reverse, int fun
*** 498,510 ****
  tree
  pushdecl (tree decl)
  {
!   /* External objects aren't nested, other objects may be.  */
!   if (DECL_EXTERNAL (decl))
!     DECL_CONTEXT (decl) = NULL_TREE;
!   else if (global_bindings_p ())
      DECL_CONTEXT (decl) = current_translation_unit;
    else
!     DECL_CONTEXT (decl) = current_function_decl;
  
    /* Put the declaration on the list.  The list of declarations is in reverse
       order. The list will be reversed later if necessary.  This needs to be
--- 498,517 ----
  tree
  pushdecl (tree decl)
  {
!   if (global_bindings_p ())
      DECL_CONTEXT (decl) = current_translation_unit;
    else
!     {
!       /* External objects aren't nested.  For debug info insert a copy
!          of the decl into the binding level.  */
!       if (DECL_EXTERNAL (decl))
! 	{
! 	  tree orig = decl;
! 	  decl = copy_node (decl);
! 	  DECL_CONTEXT (orig) = NULL_TREE;
! 	}
!       DECL_CONTEXT (decl) = current_function_decl;
!     }
  
    /* Put the declaration on the list.  The list of declarations is in reverse
       order. The list will be reversed later if necessary.  This needs to be
Index: gcc/testsuite/gfortran.dg/lto/pr47839_0.f90
===================================================================
*** gcc/testsuite/gfortran.dg/lto/pr47839_0.f90	(revision 0)
--- gcc/testsuite/gfortran.dg/lto/pr47839_0.f90	(revision 0)
***************
*** 0 ****
--- 1,8 ----
+ ! { dg-lto-do link }
+ ! { dg-lto-options {{ -g -flto }} }
+ ! { dg-extra-ld-options "-r -nostdlib" }
+ 
+ MODULE globalvar_mod
+ integer        :: xstop
+ CONTAINS
+ END MODULE globalvar_mod
Index: gcc/testsuite/gfortran.dg/lto/pr47839_1.f90
===================================================================
*** gcc/testsuite/gfortran.dg/lto/pr47839_1.f90	(revision 0)
--- gcc/testsuite/gfortran.dg/lto/pr47839_1.f90	(revision 0)
***************
*** 0 ****
--- 1,7 ----
+ MODULE PEC_mod
+ CONTAINS
+ SUBROUTINE PECapply(Ex)
+ USE globalvar_mod, ONLY : xstop
+ real(kind=8), dimension(1:xstop), intent(inout) :: Ex
+ END SUBROUTINE PECapply
+ END MODULE PEC_mod