[RFA] fix maint space

[Richard Henderson <rth@twiddle.net>]

Seems awfully dangerous to depend on environ living at some
specific address.  Indeed, for alpha-linux it lives in libc.so.

It would seem more robust to either

  (1) Just cache the brk at the beginning of execution.
  (2) Use a special statistics routine provided by the
      malloc implementation, since the heap may be split
      into discontiguous pieces.

Here I do the former.  Ok?


r~



	* top.h (lim_at_start): Declare.
	* main.c (captured_main): Set it.
	* top.c (lim_at_start): Define.
	(command_loop): Use it instead of &environ.
	* event-top.c (command_handler): Likewise.

Index: event-top.c
===================================================================
RCS file: /cvs/src/src/gdb/event-top.c,v
retrieving revision 1.26
diff -c -p -d -u -r1.26 event-top.c
--- event-top.c	12 Feb 2003 15:31:30 -0000	1.26
+++ event-top.c	1 Jun 2003 06:56:23 -0000
@@ -492,10 +492,8 @@ command_handler (char *command)
   if (display_space)
     {
 #ifdef HAVE_SBRK
-      extern char **environ;
       char *lim = (char *) sbrk (0);
-
-      space_at_cmd_start = (long) (lim - (char *) &environ);
+      space_at_cmd_start = lim - lim_at_start;
 #endif
     }
 
@@ -538,9 +536,8 @@ command_handler (char *command)
       if (display_space)
 	{
 #ifdef HAVE_SBRK
-	  extern char **environ;
 	  char *lim = (char *) sbrk (0);
-	  long space_now = lim - (char *) &environ;
+	  long space_now = lim - lim_at_start;
 	  long space_diff = space_now - space_at_cmd_start;
 
 	  printf_unfiltered ("Space used: %ld (%c%ld for this command)\n",
@@ -577,9 +574,8 @@ command_line_handler_continuation (struc
   if (display_space)
     {
 #ifdef HAVE_SBRK
-      extern char **environ;
       char *lim = (char *) sbrk (0);
-      long space_now = lim - (char *) &environ;
+      long space_now = lim - lim_at_start;
       long space_diff = space_now - space_at_cmd_start;
 
       printf_unfiltered ("Space used: %ld (%c%ld for this command)\n",
Index: main.c
===================================================================
RCS file: /cvs/src/src/gdb/main.c,v
retrieving revision 1.32
diff -c -p -d -u -r1.32 main.c
--- main.c	20 Mar 2003 22:25:16 -0000	1.32
+++ main.c	1 Jun 2003 06:56:24 -0000
@@ -168,6 +168,10 @@ captured_main (void *data)
   /* This needs to happen before the first use of malloc.  */
   init_malloc (NULL);
 
+#ifdef HAVE_SBRK
+  lim_at_start = (char *) sbrk (0);
+#endif
+
 #if defined (ALIGN_STACK_ON_STARTUP)
   i = (int) &count & 0x3;
   if (i != 0)
Index: top.c
===================================================================
RCS file: /cvs/src/src/gdb/top.c,v
retrieving revision 1.71
diff -c -p -d -u -r1.71 top.c
--- top.c	6 Feb 2003 01:19:12 -0000	1.71
+++ top.c	1 Jun 2003 06:56:26 -0000
@@ -171,6 +171,11 @@ int target_executing = 0;
 /* Level of control structure.  */
 static int control_level;
 
+/* Sbrk location on entry to main.  Used for statistics only.  */
+#ifdef HAVE_SBRK
+char *lim_at_start;
+#endif
+
 /* Signal to catch ^Z typed while reading a command: SIGTSTP or SIGCONT.  */
 
 #ifndef STOP_SIGNAL
@@ -782,10 +787,8 @@ command_loop (void)
       if (display_space)
 	{
 #ifdef HAVE_SBRK
-	  extern char **environ;
 	  char *lim = (char *) sbrk (0);
-
-	  space_at_cmd_start = (long) (lim - (char *) &environ);
+	  space_at_cmd_start = lim - lim_at_start;
 #endif
 	}
 
@@ -805,9 +808,8 @@ command_loop (void)
       if (display_space)
 	{
 #ifdef HAVE_SBRK
-	  extern char **environ;
 	  char *lim = (char *) sbrk (0);
-	  long space_now = lim - (char *) &environ;
+	  long space_now = lim - lim_at_start;
 	  long space_diff = space_now - space_at_cmd_start;
 
 	  printf_unfiltered ("Space used: %ld (%c%ld for this command)\n",
Index: top.h
===================================================================
RCS file: /cvs/src/src/gdb/top.h,v
retrieving revision 1.7
diff -c -p -d -u -r1.7 top.h
--- top.h	19 Mar 2002 19:00:04 -0000	1.7
+++ top.h	1 Jun 2003 06:56:26 -0000
@@ -70,5 +70,6 @@ extern char *source_error;
 extern char *source_pre_error;
 extern int history_expansion_p;
 extern int server_command;
+extern char *lim_at_start;
 
 #endif