Re: RFC: allow breakpoints on labels

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:

Tom> This has been sitting around for almost a year:
Tom> http://sourceware.org/ml/gdb-patches/2009-08/msg00322.html

I needed to set the pspace on the new sal, and I took the opportunity to
update the .exp file as well.  Here is the patch I am committing.

Tom

2010-07-13  Tom Tromey  <tromey@redhat.com>

	PR breakpoints/8357:
	* symtab.h (domain_enum_tag) <LABEL_DOMAIN>: Update comment.
	* linespec.c (decode_line_1): Update comment.  Call decode_label.
	(decode_label): New function.
	(symbol_found): Handle LOC_LABEL.
	* dwarf2read.c (new_symbol) <DW_TAG_label>: Set symbol's type and
	domain.  Call add_symbol_to_list.

2010-07-13  Tom Tromey  <tromey@redhat.com>

	* gdb.texinfo (Specify Location): Document labels.

2010-07-13  Tom Tromey  <tromey@redhat.com>

	* gdb.base/label.exp: New file.
	* gdb.base/label.c: New file.

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.412
diff -u -r1.412 dwarf2read.c
--- dwarf2read.c	13 Jul 2010 15:09:03 -0000	1.412
+++ dwarf2read.c	13 Jul 2010 20:04:43 -0000
@@ -8807,7 +8807,10 @@
 	    {
 	      SYMBOL_VALUE_ADDRESS (sym) = DW_ADDR (attr) + baseaddr;
 	    }
+	  SYMBOL_TYPE (sym) = objfile_type (objfile)->builtin_core_addr;
+	  SYMBOL_DOMAIN (sym) = LABEL_DOMAIN;
 	  SYMBOL_CLASS (sym) = LOC_LABEL;
+	  add_symbol_to_list (sym, cu->list_in_scope);
 	  break;
 	case DW_TAG_subprogram:
 	  /* SYMBOL_BLOCK_VALUE (sym) will be filled in later by
Index: linespec.c
===================================================================
RCS file: /cvs/src/src/gdb/linespec.c,v
retrieving revision 1.103
diff -u -r1.103 linespec.c
--- linespec.c	14 May 2010 23:41:04 -0000	1.103
+++ linespec.c	13 Jul 2010 20:04:43 -0000
@@ -122,6 +122,9 @@
 					       char ***canonical,
 					       struct symtab *file_symtab);
 
+static int decode_label (char *copy, char ***canonical,
+			 struct symtabs_and_lines *result);
+
 static struct symtabs_and_lines decode_variable (char *copy,
 						 int funfirstline,
 						 char ***canonical,
@@ -672,6 +675,7 @@
    FILE:LINENUM -- that line in that file.  PC returned is 0.
    FUNCTION -- line number of openbrace of that function.
    PC returned is the start of the function.
+   LABEL -- a label in the current scope
    VARIABLE -- line number of definition of that variable.
    PC returned is 0.
    FILE:FUNCTION -- likewise, but prefer functions in that file.
@@ -903,6 +907,16 @@
     return decode_dollar (copy, funfirstline, default_symtab,
 			  canonical, file_symtab);
 
+  /* Try the token as a label, but only if no file was specified,
+     because we can only really find labels in the current scope.  */
+
+  if (!file_symtab)
+    {
+      struct symtabs_and_lines label_result;
+      if (decode_label (copy, canonical, &label_result))
+	return label_result;
+    }
+
   /* Look up that token as a variable.
      If file specified, use that file's per-file block to start with.  */
 
@@ -1838,6 +1852,27 @@
 
 
 
+/* A helper for decode_line_1 that tries to find a label.  The label
+   is searched for in the current block.
+   COPY is the name of the label to find.
+   CANONICAL is the same as the "canonical" argument to decode_line_1.
+   RESULT is a pointer to a symtabs_and_lines structure which will be
+   filled in on success.
+   This function returns 1 if a label was found, 0 otherwise.  */
+
+static int
+decode_label (char *copy, char ***canonical, struct symtabs_and_lines *result)
+{
+  struct symbol *sym;
+
+  sym = lookup_symbol (copy, get_selected_block (0), LABEL_DOMAIN, 0);
+
+  if (sym != NULL)
+    *result = symbol_found (0, canonical, copy, sym, NULL);
+
+  return sym != NULL;
+}
+
 /* Decode a linespec that's a variable.  If FILE_SYMTAB is non-NULL,
    look in that symtab's static variables first.  If NOT_FOUND_PTR is not NULL and
    the function cannot be found, store boolean true in the location pointed to
@@ -1917,7 +1952,7 @@
     }
   else
     {
-      if (funfirstline)
+      if (funfirstline && SYMBOL_CLASS (sym) != LOC_LABEL)
 	error (_("\"%s\" is not a function"), copy);
       else if (SYMBOL_LINE (sym) != 0)
 	{
@@ -1928,6 +1963,7 @@
 	  memset (&values.sals[0], 0, sizeof (values.sals[0]));
 	  values.sals[0].symtab = SYMBOL_SYMTAB (sym);
 	  values.sals[0].line = SYMBOL_LINE (sym);
+	  values.sals[0].pspace = SYMTAB_PSPACE (SYMBOL_SYMTAB (sym));
 	  return values;
 	}
       else
Index: symtab.h
===================================================================
RCS file: /cvs/src/src/gdb/symtab.h,v
retrieving revision 1.154
diff -u -r1.154 symtab.h
--- symtab.h	28 Jun 2010 20:35:52 -0000	1.154
+++ symtab.h	13 Jul 2010 20:04:44 -0000
@@ -377,8 +377,7 @@
 
   STRUCT_DOMAIN,
 
-  /* LABEL_DOMAIN may be used for names of labels (for gotos);
-     currently it is not used and labels are not recorded at all.  */
+  /* LABEL_DOMAIN may be used for names of labels (for gotos).  */
 
   LABEL_DOMAIN,
 
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.737
diff -u -r1.737 gdb.texinfo
--- doc/gdb.texinfo	1 Jul 2010 17:40:04 -0000	1.737
+++ doc/gdb.texinfo	13 Jul 2010 20:04:47 -0000
@@ -6330,6 +6330,13 @@
 function name to avoid ambiguity when there are identically named
 functions in different source files.
 
+@item @var{label}
+Specifies the line at which the label named @var{label} appears.
+@value{GDBN} searches for the label in the function corresponding to
+the currently selected stack frame.  If there is no current selected
+stack frame (for instance, if the inferior is not running), then
+@value{GDBN} will not search for a label.
+
 @item *@var{address}
 Specifies the program address @var{address}.  For line-oriented
 commands, such as @code{list} and @code{edit}, this specifies a source
Index: testsuite/gdb.base/label.c
===================================================================
RCS file: testsuite/gdb.base/label.c
diff -N testsuite/gdb.base/label.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/label.c	13 Jul 2010 20:04:49 -0000
@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int
+main (int argc, char *argv)
+{
+  int i = 0;
+  goto there;
+
+here:
+  printf("not here\n");
+  i = 1;
+  
+there:
+  printf("but here\n");
+  if (i == 0)
+    goto here;
+
+done:
+  return 0;
+}
+
Index: testsuite/gdb.base/label.exp
===================================================================
RCS file: testsuite/gdb.base/label.exp
diff -N testsuite/gdb.base/label.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/label.exp	13 Jul 2010 20:04:49 -0000
@@ -0,0 +1,59 @@
+# Copyright 2010 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+
+if [is_remote target] then {
+    return 0
+}
+
+
+#
+# test running programs
+#
+
+set testfile "label"
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+if { [prepare_for_testing ${testfile}.exp $testfile ${testfile}.c debug] } {
+    untested label.exp
+    return -1
+}
+
+
+if {![runto_main]} {
+  fail "label tests suppressed"
+  return -1
+}
+
+gdb_test "break here" \
+  "Breakpoint.*at.*" \
+  "breakpoint here"
+
+gdb_test "break there" \
+  "Breakpoint.*at.*" \
+  "breakpoint there"
+
+gdb_test "cont" \
+  "Breakpoint 3,.*" \
+  "continue to 'there'"
+
+gdb_test "cont" \
+  "Breakpoint 2,.*" \
+  "continue to 'here'"