Patch: Handle relative paths in .debug_line

[Bryce McKinlay <mckinlay at redhat dot com>]

When debugging mainline gcc, GDB has a problem locating source for files 
which are only referenced from .debug_line. For example: debugging gcj, 
and trying to put a breakpoint on the parse.y file, I get the following:

Breakpoint 1, lookup_method_invoke (lc=1, cl=0xf6dee5f0, class=0xf6def244,
   name=0xf6dee550, arg_list=0xf6e574b0) at parse.y:10956
10956   parse.y: No such file or directory.
       in parse.y
(gdb) info source
Current source file is parse.y
Compilation directory is ../../gcc/java
Source language is c.
Compiled with unknown debugging format.
Does not include preprocessor macro info.

This is because the contents of the directory table in .debug_line can 
be paths relative to the DW_AT_comp_dir:


The Directory Table:
 ../../gcc/java
 java
 /usr/include/bits
 .
 ../../gcc
 ../../gcc/../libcpp/include
 ../../gcc/config/i386
 ../../gcc/../include
 /local/gcc-clean/lib/gcc/i686-pc-linux-gnu/3.5.0/include
 /usr/include

The File Name Table:
 Entry    Dir    Time    Size    Name
 1    1    0    0    keyword.h
 2    1    0    0    lex.c
 3    2    0    0    parse.c
 4    1    0    0    parse.y
... etc...

    DW_AT_comp_dir    : (indirect string, offset: 0x658c): 
/home/mckinlay/cvs/gcc-really-clean/build/gcc   

This patch fixes the problem by appending the path from the directory 
table, if it is not absolute already, to the DW_AT_comp_dir path when 
creating subfiles from the .debug_line info.

OK to commit?

Bryce


2004-07-22  Bryce McKinlay  <mckinlay@redhat.com>

	* dwarf2read.c (dwarf_decode_lines): Pass comp_dir to
	dwarf2_start_subfile.
	(dwarf2_start_subfile): New comp_dir parameter.	Handle relative paths
	in .debug_line by appending them to comp_dir. Use make_cleanup to
	free strings used in directory concatenation.
	
Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.156
diff -u -r1.156 dwarf2read.c
--- dwarf2read.c	6 Jul 2004 19:29:30 -0000	1.156
+++ dwarf2read.c	22 Jul 2004 23:07:41 -0000
@@ -762,7 +762,7 @@
 static void dwarf_decode_lines (struct line_header *, char *, bfd *,
 				struct dwarf2_cu *, struct partial_symtab *);
 
-static void dwarf2_start_subfile (char *, char *);
+static void dwarf2_start_subfile (char *, char *, char *);
 
 static struct symbol *new_symbol (struct die_info *, struct type *,
 				  struct dwarf2_cu *);
@@ -5951,12 +5951,10 @@
 	     directory and file name numbers in the statement program
 	     are 1-based.  */
           struct file_entry *fe = &lh->file_names[file - 1];
-          char *dir;
+          char *dir = NULL;
           if (fe->dir_index)
             dir = lh->include_dirs[fe->dir_index - 1];
-          else
-            dir = comp_dir;
-	  dwarf2_start_subfile (fe->name, dir);
+	  dwarf2_start_subfile (fe->name, dir, comp_dir);
 	}
 
       /* Decode the table. */
@@ -6044,17 +6042,15 @@
                    but the directory and file name numbers in the
                    statement program are 1-based.  */
                 struct file_entry *fe;
-                char *dir;
+                char *dir = NULL;
                 file = read_unsigned_leb128 (abfd, line_ptr, &bytes_read);
                 line_ptr += bytes_read;
                 fe = &lh->file_names[file - 1];
                 fe->included_p = 1;
                 if (fe->dir_index)
                   dir = lh->include_dirs[fe->dir_index - 1];
-                else
-                  dir = comp_dir;
                 if (!decode_for_pst_p)
-                  dwarf2_start_subfile (fe->name, dir);
+                  dwarf2_start_subfile (fe->name, dir, comp_dir);
               }
 	      break;
 	    case DW_LNS_set_column:
@@ -6112,7 +6108,8 @@
 
 /* Start a subfile for DWARF.  FILENAME is the name of the file and
    DIRNAME the name of the source directory which contains FILENAME
-   or NULL if not known.
+   or NULL if not known.  COMP_DIR is the value of DW_AT_comp_dir.  If
+   DIRNAME specifies a relative path, it is appended to COMP_DIR.
    This routine tries to keep line numbers from identical absolute and
    relative file names in a common subfile.
 
@@ -6131,28 +6128,44 @@
    subfile, so that `break /srcdir/list0.c:1' works as expected.  */
 
 static void
-dwarf2_start_subfile (char *filename, char *dirname)
+dwarf2_start_subfile (char *filename, char *dirname, char *comp_dir)
 {
+  char *fullname;
+  struct subfile *subfile;
+  struct cleanup *back_to = make_cleanup (null_cleanup, 0);
+
+  /* If we have a relative dirname, append comp_dir to it.  */
+  if (dirname != NULL && !IS_ABSOLUTE_PATH (dirname))
+    {
+      dirname = concat (comp_dir, "/", dirname, NULL);
+      make_cleanup (xfree, dirname);
+    }
+  else if (dirname == NULL)
+    dirname = comp_dir;
+
   /* If the filename isn't absolute, try to match an existing subfile
      with the full pathname.  */
 
-  if (!IS_ABSOLUTE_PATH (filename) && dirname != NULL)
+  if (!IS_ABSOLUTE_PATH (filename))
     {
-      struct subfile *subfile;
-      char *fullname = concat (dirname, "/", filename, NULL);
+      fullname = concat (dirname, "/", filename, NULL);
+      make_cleanup (xfree, fullname);
+    }
+  else
+    fullname = filename;
 
-      for (subfile = subfiles; subfile; subfile = subfile->next)
+  for (subfile = subfiles; subfile; subfile = subfile->next)
+    {
+      if (FILENAME_CMP (subfile->name, fullname) == 0)
 	{
-	  if (FILENAME_CMP (subfile->name, fullname) == 0)
-	    {
-	      current_subfile = subfile;
-	      xfree (fullname);
-	      return;
-	    }
+	  current_subfile = subfile;
+	  do_cleanups (back_to);
+	  return;
 	}
-      xfree (fullname);
     }
+
   start_subfile (filename, dirname);
+  do_cleanups (back_to);
 }
 
 static void