Re: PR 12001, --defsym

[Alan Modra <amodra at gmail dot com>]

On Thu, Jan 13, 2011 at 11:35:39PM +1030, Alan Modra wrote:
> Given this bug report and Daniel's objections over using a linker
> script assignment to control ld behaviour, I've implemented a new
> LD_FEATURE linker script keyword.

I've kept the new code in open_input_bfds handling early creation of
--defsym symbols, but only handle --defsym assignments there so we
won't get an error if a script defines a symbol that is also defined
in an object file.  LD_FEATURE is designed to be extensible;  At the 
moment we just have LD_FEATURE ("SANE_EXPR").

	PR ld/12356
	* ld.texinfo (Miscellaneous Commands): Describe LD_FEATURE.
	(Expression Section): Update.
	* ld.h (ld_config_type): Add sane_expr.
	* ldgram.y (ifile_p1): Add LD_FEATURE.
	* ldlex.l (LD_FEATYRE): New.
	* ldemul.c (after_parse_default): Delete code handling ld_compatibility.
	* ldexp.h (struct ldexp_control): Delete uses_defined.
	* ldexp.c: Remove all uses of uses_defined.
	(fold_name): Test config.sane_expr rather than ld_compatibility.
	(exp_fold_tree_1): Likewise.  Adjust handling of assignments
	during first phase.
	* ldlang.h (ld_compatibility): Delete.
	(lang_ld_feature): Declare.
	* ldlang.c (ld_compatibility): Delete.
	(open_input_bfds): Only handle assignments for --defsym.
	(lang_ld_feature): New function.

Index: ld/ld.texinfo
===================================================================
RCS file: /cvs/src/src/ld/ld.texinfo,v
retrieving revision 1.269
diff -u -p -r1.269 ld.texinfo
--- ld/ld.texinfo	20 Dec 2010 13:00:12 -0000	1.269
+++ ld/ld.texinfo	13 Jan 2011 13:13:58 -0000
@@ -3344,6 +3344,13 @@ of the names used by the BFD library (@p
 architecture of an object file by using the @code{objdump} program with
 the @samp{-f} option.
 @end ifclear
+
+@item LD_FEATURE(@var{string})
+@kindex LD_FEATURE(@var{string})
+This command may be used to modify @command{ld} behavior.  If
+@var{string} is @code{"SANE_EXPR"} then absolute symbols and numbers
+in a script are simply treated as numbers everywhere.
+@xref{Expression Section}.
 @end table
 
 @node Assignments
@@ -5503,15 +5510,15 @@ section relative symbols and for builtin
 address, such as @code{ADDR}, @code{LOADADDR}, @code{ORIGIN} and
 @code{SEGMENT_START}.  Other terms are simply numbers, or are builtin
 functions that return a non-address value, such as @code{LENGTH}.
-One complication is that unless you assign @code{__ld_compatibility}
-a value of 221 or larger, numbers and absolute symbols are treated
+One complication is that unless you set @code{LD_FEATURE ("SANE_EXPR")}
+(@pxref{Miscellaneous Commands}), numbers and absolute symbols are treated
 differently depending on their location, for compatibility with older
 versions of @code{ld}.  Expressions appearing outside an output
 section definition treat all numbers as absolute addresses.
 Expressions appearing inside an output section definition treat
-absolute symbols as numbers.  If @code{__ld_compatibility} is assigned
-a value larger than 221, then absolute symbols and numbers are simply
-treated as numbers everywhere.
+absolute symbols as numbers.  If @code{LD_FEATURE ("SANE_EXPR")} is
+given, then absolute symbols and numbers are simply treated as numbers
+everywhere.
 
 In the following simple example,
 
Index: ld/ld.h
===================================================================
RCS file: /cvs/src/src/ld/ld.h,v
retrieving revision 1.47
diff -u -p -r1.47 ld.h
--- ld/ld.h	15 Dec 2010 14:56:37 -0000	1.47
+++ ld/ld.h	13 Jan 2011 13:13:53 -0000
@@ -292,6 +292,10 @@ typedef struct {
      on the command line.  */
   bfd_boolean only_cmd_line_lib_dirs;
 
+  /* If set, numbers and absolute symbols are simply treated as
+     numbers everywhere.  */
+  bfd_boolean sane_expr;
+
   /* The rpath separation character.  Usually ':'.  */
   char rpath_separator;
 
Index: ld/ldgram.y
===================================================================
RCS file: /cvs/src/src/ld/ldgram.y,v
retrieving revision 1.64
diff -u -p -r1.64 ldgram.y
--- ld/ldgram.y	13 Jan 2011 13:06:22 -0000	1.64
+++ ld/ldgram.y	13 Jan 2011 13:14:00 -0000
@@ -134,6 +134,7 @@ static int error_index;
 %token INCLUDE
 %token MEMORY
 %token REGION_ALIAS
+%token LD_FEATURE
 %token NOLOAD DSECT COPY INFO OVERLAY
 %token DEFINED TARGET_K SEARCH_DIR MAP ENTRY
 %token <integer> NEXT
@@ -357,6 +358,8 @@ ifile_p1:
 		{ lang_add_insert ($3, 1); }
 	|	REGION_ALIAS '(' NAME ',' NAME ')'
 		{ lang_memory_region_alias ($3, $5); }
+	|	LD_FEATURE '(' NAME ')'
+		{ lang_ld_feature ($3); }
 	;
 
 input_list:
Index: ld/ldlex.l
===================================================================
RCS file: /cvs/src/src/ld/ldlex.l,v
retrieving revision 1.48
diff -u -p -r1.48 ldlex.l
--- ld/ldlex.l	15 Dec 2010 14:56:37 -0000	1.48
+++ ld/ldlex.l	13 Jan 2011 13:14:06 -0000
@@ -241,6 +241,7 @@ V_IDENTIFIER [*?.$_a-zA-Z\[\]\-\!\^\\]([
 <BOTH,SCRIPT,EXPRESSION,MRI>";"		{ RTOKEN(';');}
 <BOTH,SCRIPT>"MEMORY"			{ RTOKEN(MEMORY);}
 <BOTH,SCRIPT>"REGION_ALIAS"		{ RTOKEN(REGION_ALIAS);}
+<BOTH,SCRIPT>"LD_FEATURE"		{ RTOKEN(LD_FEATURE);}
 <BOTH,SCRIPT,EXPRESSION>"ORIGIN"	{ RTOKEN(ORIGIN);}
 <BOTH,SCRIPT>"VERSION"			{ RTOKEN(VERSIONK);}
 <EXPRESSION,BOTH,SCRIPT>"BLOCK"		{ RTOKEN(BLOCK);}
Index: ld/ldemul.c
===================================================================
RCS file: /cvs/src/src/ld/ldemul.c,v
retrieving revision 1.35
diff -u -p -r1.35 ldemul.c
--- ld/ldemul.c	20 Dec 2010 13:00:13 -0000	1.35
+++ ld/ldemul.c	13 Jan 2011 13:14:00 -0000
@@ -226,16 +226,6 @@ after_parse_default (void)
 void
 after_open_default (void)
 {
-  struct bfd_link_hash_entry *h;
-
-  h = bfd_wrapped_link_hash_lookup (link_info.output_bfd,
-				    &link_info,
-				    "__ld_compatibility",
-				    FALSE, FALSE, TRUE);
-  if (h != NULL
-      && (h->type == bfd_link_hash_defined
-	  || h->type == bfd_link_hash_defweak))
-    ld_compatibility = h->u.def.value;
 }
 
 void
Index: ld/ldexp.h
===================================================================
RCS file: /cvs/src/src/ld/ldexp.h,v
retrieving revision 1.27
diff -u -p -r1.27 ldexp.h
--- ld/ldexp.h	13 Jan 2011 13:06:22 -0000	1.27
+++ ld/ldexp.h	13 Jan 2011 13:14:00 -0000
@@ -132,8 +132,6 @@ struct ldexp_control {
   /* Working results.  */
   etree_value_type result;
   bfd_vma dot;
-  /* Set if an expression contains DEFINED().  */
-  bfd_boolean uses_defined;
 
   /* Current dot and section passed to ldexp folder.  */
   bfd_vma *dotp;
Index: ld/ldexp.c
===================================================================
RCS file: /cvs/src/src/ld/ldexp.c,v
retrieving revision 1.91
diff -u -p -r1.91 ldexp.c
--- ld/ldexp.c	13 Jan 2011 13:06:22 -0000	1.91
+++ ld/ldexp.c	13 Jan 2011 13:14:00 -0000
@@ -512,7 +512,6 @@ fold_name (etree_type *tree)
       break;
 
     case DEFINED:
-      expld.uses_defined = TRUE;
       if (expld.phase == lang_first_phase_enum)
 	lang_track_definedness (tree->name.name);
       else
@@ -564,7 +563,7 @@ fold_name (etree_type *tree)
 		}
 	      else if (output_section == bfd_abs_section_ptr
 		       && (expld.section != bfd_abs_section_ptr
-			   || ld_compatibility >= 221))
+			   || config.sane_expr))
 		new_number (h->u.def.value + h->u.def.section->output_offset);
 	      else
 		new_rel (h->u.def.value + h->u.def.section->output_offset,
@@ -712,7 +711,7 @@ exp_fold_tree_1 (etree_type *tree)
     {
     case etree_value:
       if (expld.section == bfd_abs_section_ptr
-	  && ld_compatibility < 221)
+	  && !config.sane_expr)
 	new_abs (tree->value.value);
       else
 	new_number (tree->value.value);
@@ -819,7 +818,8 @@ exp_fold_tree_1 (etree_type *tree)
 	  exp_fold_tree_1 (tree->assign.src);
 	  if (expld.result.valid_p
 	      || (expld.phase == lang_first_phase_enum
-		  && !expld.uses_defined))
+		  && tree->type.node_class == etree_assign
+		  && tree->assign.hidden))
 	    {
 	      if (h == NULL)
 		{
@@ -883,7 +883,6 @@ exp_fold_tree (etree_type *tree, asectio
   expld.dot = *dotp;
   expld.dotp = dotp;
   expld.section = current_section;
-  expld.uses_defined = FALSE;
   exp_fold_tree_1 (tree);
 }
 
@@ -893,7 +892,6 @@ exp_fold_tree_no_dot (etree_type *tree)
   expld.dot = 0;
   expld.dotp = NULL;
   expld.section = bfd_abs_section_ptr;
-  expld.uses_defined = FALSE;
   exp_fold_tree_1 (tree);
 }
 
Index: ld/ldlang.h
===================================================================
RCS file: /cvs/src/src/ld/ldlang.h,v
retrieving revision 1.93
diff -u -p -r1.93 ldlang.h
--- ld/ldlang.h	20 Dec 2010 13:00:14 -0000	1.93
+++ ld/ldlang.h	13 Jan 2011 13:14:03 -0000
@@ -469,7 +469,6 @@ extern bfd_boolean entry_from_cmdline;
 extern lang_statement_list_type file_chain;
 extern lang_statement_list_type input_file_chain;
 
-extern int ld_compatibility;
 extern int lang_statement_iteration;
 extern bfd_boolean missing_file;
 
@@ -651,4 +650,7 @@ extern bfd_boolean
 ldlang_override_segment_assignment
   (struct bfd_link_info *, bfd *, asection *, asection *, bfd_boolean);
 
+extern void
+lang_ld_feature (char *);
+
 #endif
Index: ld/ldlang.c
===================================================================
RCS file: /cvs/src/src/ld/ldlang.c,v
retrieving revision 1.358
diff -u -p -r1.358 ldlang.c
--- ld/ldlang.c	13 Jan 2011 13:06:22 -0000	1.358
+++ ld/ldlang.c	13 Jan 2011 13:14:03 -0000
@@ -108,7 +108,6 @@ bfd_boolean delete_output_file_on_failur
 struct lang_phdr *lang_phdr_list;
 struct lang_nocrossrefs *nocrossref_list;
 bfd_boolean missing_file = FALSE;
-int ld_compatibility;
 
  /* Functions that traverse the linker script and might evaluate
     DEFINED() need to increment this.  */
@@ -3250,7 +3249,9 @@ open_input_bfds (lang_statement_union_ty
 	    }
 	  break;
 	case lang_assignment_statement_enum:
-	  exp_fold_tree_no_dot (s->assignment_statement.exp);
+	  if (s->assignment_statement.exp->assign.hidden)
+	    /* This is from a --defsym on the command line.  */
+	    exp_fold_tree_no_dot (s->assignment_statement.exp);
 	  break;
 	default:
 	  break;
@@ -7845,3 +7846,32 @@ lang_append_dynamic_list_cpp_new (void)
 
   lang_append_dynamic_list (dynamic);
 }
+
+/* Scan a space and/or comma separated string of features.  */
+
+void
+lang_ld_feature (char *str)
+{
+  char *p, *q;
+
+  p = str;
+  while (*p)
+    {
+      char sep;
+      while (*p == ',' || ISSPACE (*p))
+	++p;
+      if (!*p)
+	break;
+      q = p + 1;
+      while (*q && *q != ',' && !ISSPACE (*q))
+	++q;
+      sep = *q;
+      *q = 0;
+      if (strcasecmp (p, "SANE_EXPR") == 0)
+	config.sane_expr = TRUE;
+      else
+	einfo (_("%X%P: unknown feature `%s'\n"), p);
+      *q = sep;
+      p = q;
+    }
+}

-- 
Alan Modra
Australia Development Lab, IBM