Re: [commit] Move legacy prev->next = ... earlier

Andrew Cagney
2003-04-05T18:21:33Z

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Did I mention that it wasn't my day. Again, the real patch :-/

Andrew

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2003-04-05 Andrew Cagney <cagney@redhat.com>

* frame.c (legacy_get_prev_frame): Link prev to next at the
function start. Update comments.

Index: frame.c
===================================================================
RCS file: /cvs/src/src/gdb/frame.c,v
retrieving revision 1.97
diff -u -r1.97 frame.c
--- frame.c 5 Apr 2003 15:39:33 -0000 1.97
+++ frame.c 5 Apr 2003 15:42:22 -0000
@@ -1029,10 +1029,7 @@
struct frame_info *prev;
int fromleaf;

- /* Allocate the new frame but do not wire it in to the frame chain.
- Some (bad) code in INIT_FRAME_EXTRA_INFO tries to look along
- frame->next to pull some fancy tricks (of course such code is, by
- definition, recursive). Try to prevent it.
+ /* Allocate the new frame.

There is no reason to worry about memory leaks, should the
remainder of the function fail. The allocated memory will be
@@ -1042,6 +1039,17 @@
prev = FRAME_OBSTACK_ZALLOC (struct frame_info);
prev->level = this_frame->level + 1;

+ /* Do not completly wire it in to the frame chain. Some (bad) code
+ in INIT_FRAME_EXTRA_INFO tries to look along frame->prev to pull
+ some fancy tricks (of course such code is, by definition,
+ recursive).
+
+ On the other hand, methods, such as get_frame_pc() and
+ get_frame_base() rely on being able to walk along the frame
+ chain. Make certain that at least they work by providing that
+ link. Of course things manipulating prev can't go back. */
+ prev->next = this_frame;
+
/* NOTE: cagney/2002-11-18: Should have been correctly setting the
frame's type here, before anything else, and not last, at the
bottom of this function. The various
@@ -1155,7 +1163,6 @@

/* Link it in. */
this_frame->prev = prev;
- prev->next = this_frame;

/* FIXME: cagney/2002-01-19: This call will go away. Instead of
initializing extra info, all frames will use the frame_cache
@@ -1230,7 +1237,6 @@

/* Link in the already allocated prev frame. */
this_frame->prev = prev;
- prev->next = this_frame;
deprecated_update_frame_base_hack (prev, address);

/* This change should not be needed, FIXME! We should determine