[branch patch] core files as symfiles

[Roland McGrath <roland at redhat dot com>]

The following patch causes core files to be implicitly read as symbol files
as well.  Using this along with my previous dwarf-frame.c patch vs current
kettenis_i386newframe-20030419-branch gdb, on Linux 2.5.69 on x86 the
backtrace of a thread in a system call from a core dump Just Works.

I've included the trivial symfile.c patch that was in with my dwarf-frame.c
patch again here too, since it's required for the corelow.c patch to work
and these patches work (but cause nothing interesting to happen)
independent of the dwarf-frame.c changes.


Thanks,
Roland


2003-05-12  Roland McGrath  <roland@redhat.com>

	* corelow.c (core_objfile): New variable.
	(core_close): If core_objfile is set, call free_objfile on it.
	(core_open): Open the core file with add_symbol_file, and save
	the struct objfile pointer in core_objfile.

	* symfile.c (symfile_bfd_open): Try bfd_check_format with bfd_core
	if bfd_object fails.

Index: corelow.c
===================================================================
RCS file: /cvs/src/src/gdb/corelow.c,v
retrieving revision 1.29
diff -B -p -u -r1.29 corelow.c
--- corelow.c	18 Jan 2003 15:55:51 -0000	1.29
+++ corelow.c	13 May 2003 02:57:07 -0000
@@ -38,6 +38,7 @@
 #include "gdbthread.h"
 #include "regcache.h"
 #include "symfile.h"
+#include "objfiles.h"
 #include <readline/readline.h>
 
 #ifndef O_BINARY
@@ -50,6 +51,8 @@
 
 static struct core_fns *core_file_fns = NULL;
 
+static struct objfile *core_objfile = NULL;
+
 /* The core_fns for a core file handler that is prepared to read the core
    file currently open on core_bfd. */
 
@@ -200,6 +203,8 @@ core_close (int quitting)
 	warning ("cannot close \"%s\": %s",
 		 name, bfd_errmsg (bfd_get_error ()));
       xfree (name);
+      if (core_objfile && core_objfile->obfd == core_bfd)
+	core_objfile->obfd = NULL;
       core_bfd = NULL;
       if (core_ops.to_sections)
 	{
@@ -209,6 +214,12 @@ core_close (int quitting)
 	}
     }
   core_vec = NULL;
+
+  if (core_objfile)
+    {
+      free_objfile (core_objfile);
+      core_objfile = NULL;
+    }
 }
 
 static void
@@ -263,6 +274,7 @@ core_open (char *filename, int from_tty)
   struct cleanup *old_chain;
   char *temp;
   bfd *temp_bfd;
+  struct objfile *temp_objfile;
   int ontop;
   int scratch_chan;
 
@@ -274,23 +286,42 @@ core_open (char *filename, int from_tty)
 	     : "No core file specified.");
     }
 
-  filename = tilde_expand (filename);
-  if (filename[0] != '/')
-    {
-      temp = concat (current_directory, "/", filename, NULL);
-      xfree (filename);
-      filename = temp;
-    }
+  old_chain = NULL;
 
-  old_chain = make_cleanup (xfree, filename);
+  /* Try to open the core file as a symbol file.  We do this first
+     so we can reuse the same bfd that the objfile points to.  */
+  temp_objfile = symbol_file_add (filename, 0, NULL, 0, 0);
+  if (temp_objfile != NULL)
+    old_chain = make_cleanup ((void (*) (void *)) free_objfile, temp_objfile);
 
-  scratch_chan = open (filename, O_BINARY | ( write_files ? O_RDWR : O_RDONLY ), 0);
-  if (scratch_chan < 0)
-    perror_with_name (filename);
+  if (temp_objfile != NULL && !write_files)
+    temp_bfd = temp_objfile->obfd;
+  else
+    {
+      /* symbol_file_add did the expansion and opening for us if it worked.  */
+
+      filename = tilde_expand (filename);
+      if (filename[0] != '/')
+	{
+	  temp = concat (current_directory, "/", filename, NULL);
+	  xfree (filename);
+	  filename = temp;
+	}
 
-  temp_bfd = bfd_fdopenr (filename, gnutarget, scratch_chan);
-  if (temp_bfd == NULL)
-    perror_with_name (filename);
+      if (old_chain == NULL)
+	old_chain = make_cleanup (xfree, filename);
+      else
+	make_cleanup (xfree, filename);
+
+      scratch_chan = open (filename,
+			   O_BINARY | (write_files ? O_RDWR : O_RDONLY), 0);
+      if (scratch_chan < 0)
+	perror_with_name (filename);
+
+      temp_bfd = bfd_fdopenr (filename, gnutarget, scratch_chan);
+      if (temp_bfd == NULL)
+	perror_with_name (filename);
+    }
 
   if (!bfd_check_format (temp_bfd, bfd_core) &&
       !gdb_check_format (temp_bfd))
@@ -299,7 +330,8 @@ core_open (char *filename, int from_tty)
       /* FIXME: should be checking for errors from bfd_close (for one thing,
          on error it does not free all the storage associated with the
          bfd).  */
-      make_cleanup_bfd_close (temp_bfd);
+      if (temp_objfile == NULL || temp_bfd != temp_objfile->obfd)
+	make_cleanup_bfd_close (temp_bfd);
       error ("\"%s\" is not a core dump: %s",
 	     filename, bfd_errmsg (bfd_get_error ()));
     }
@@ -308,6 +340,7 @@ core_open (char *filename, int from_tty)
 
   discard_cleanups (old_chain);	/* Don't free filename any more */
   unpush_target (&core_ops);
+  core_objfile = temp_objfile;
   core_bfd = temp_bfd;
   old_chain = make_cleanup (core_close_cleanup, 0 /*ignore*/);
 
--- symfile.c.~1.93.~	Fri Apr  4 14:29:12 2003
+++ symfile.c	Mon May 12 02:04:07 2003
@@ -1338,7 +1338,9 @@ symfile_bfd_open (char *name)
     }
   sym_bfd->cacheable = 1;
 
-  if (!bfd_check_format (sym_bfd, bfd_object))
+  if (!bfd_check_format (sym_bfd, bfd_object)
+      /* Yes, Virginia, core files can have symbols!  */
+      && !bfd_check_format (sym_bfd, bfd_core))
     {
       /* FIXME: should be checking for errors from bfd_close (for one thing,
          on error it does not free all the storage associated with the