Re: RFC: one approach to fixing PR 14100

Tom Tromey
2012-08-06T15:31:20Z

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

Tom> Then we need a cleanup instead.
Tom> I'll look at it on Monday.

Here it is.
I regression-tested it on x86-64 Fedora 16.

Tom

* dwarf2-frame.c (clear_pointer_cleanup): New function.
(dwarf2_frame_cache): Use it.
* frame-unwind.h (frame_sniffer_ftype): Document prologue
cache initialization constraint.

diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index 741a103..986aaea 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -994,10 +994,20 @@ struct dwarf2_frame_cache
void *tailcall_cache;
};

+/* A cleanup that sets a pointer to NULL. */
+
+static void
+clear_pointer_cleanup (void *arg)
+{
+ void **ptr = arg;
+
+ *ptr = NULL;
+}
+
static struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
{
- struct cleanup *old_chain;
+ struct cleanup *reset_cache_cleanup, *old_chain;
struct gdbarch *gdbarch = get_frame_arch (this_frame);
const int num_regs = gdbarch_num_regs (gdbarch)
+ gdbarch_num_pseudo_regs (gdbarch);
@@ -1017,6 +1027,7 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
*this_cache = cache;
+ reset_cache_cleanup = make_cleanup (clear_pointer_cleanup, this_cache);

/* Allocate and initialize the frame state. */
fs = XZALLOC (struct dwarf2_frame_state);
@@ -1111,6 +1122,7 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
{
cache->unavailable_retaddr = 1;
do_cleanups (old_chain);
+ discard_cleanups (reset_cache_cleanup);
return cache;
}

@@ -1226,6 +1238,7 @@ incomplete CFI data; unspecified registers (e.g., %s) at %s"),
(entry_cfa_sp_offset_p
? &entry_cfa_sp_offset : NULL));

+ discard_cleanups (reset_cache_cleanup);
return cache;
}

diff --git a/gdb/frame-unwind.h b/gdb/frame-unwind.h
index f82d763..aa58640 100644
--- a/gdb/frame-unwind.h
+++ b/gdb/frame-unwind.h
@@ -44,7 +44,9 @@ struct value;

/* Given THIS frame, take a whiff of its registers (namely
the PC and attributes) and if SELF is the applicable unwinder,
- return non-zero. Possibly also initialize THIS_PROLOGUE_CACHE. */
+ return non-zero. Possibly also initialize THIS_PROLOGUE_CACHE; but
+ only if returning 1. Initializing THIS_PROLOGUE_CACHE in other
+ cases (0 return, or exception) is invalid. */

typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
struct frame_info *this_frame,