{
CORE_ADDR address = 0;
struct frame_info *prev;
- int fromleaf = 0;
+ int fromleaf;
char *name;
- /* If the requested entry is in the cache, return it.
- Otherwise, figure out what the address should be for the entry
- we're about to add to the cache. */
-
- if (!next_frame)
+ /* Return the inner-most frame, when the caller passes in NULL. */
+ /* NOTE: cagney/2002-11-09: Not sure how this would happen. The
+ caller should have previously obtained a valid frame using
+ get_selected_frame() and then called this code - only possibility
+ I can think of is code behaving badly. */
+ if (next_frame == NULL)
{
-#if 0
- /* This screws value_of_variable, which just wants a nice clean
- NULL return from block_innermost_frame if there are no frames.
- I don't think I've ever seen this message happen otherwise.
- And returning NULL here is a perfectly legitimate thing to do. */
- if (!current_frame)
- {
- error ("You haven't set up a process's stack to examine.");
- }
-#endif
-
+ /* NOTE: cagney/2002-11-09: There was a code segment here that
+ would error out when CURRENT_FRAME was NULL. The comment
+ that went with it made the claim ...
+
+ ``This screws value_of_variable, which just wants a nice
+ clean NULL return from block_innermost_frame if there are no
+ frames. I don't think I've ever seen this message happen
+ otherwise. And returning NULL here is a perfectly legitimate
+ thing to do.''
+
+ Per the above, this code shouldn't even be called with a NULL
+ NEXT_FRAME. */
return current_frame;
}
- /* If we have the prev one, return it */
+ /* If we have the prev one, return it. */
if (next_frame->prev)
+ /* FIXME: cagney/2002-11-09: Rather than relying on ->PREV being
+ non-NULL, there should be a predicate (->prev_p?). That would
+ stop this function constantly trying to chain beyond the
+ outermost frame. */
return next_frame->prev;
/* On some machines it is possible to call a function without
or isn't leafless. */
/* Still don't want to worry about this except on the innermost
- frame. This macro will set FROMLEAF if NEXT_FRAME is a
- frameless function invocation. */
- if (!(next_frame->next))
- {
- fromleaf = FRAMELESS_FUNCTION_INVOCATION (next_frame);
- if (fromleaf)
- address = FRAME_FP (next_frame);
- }
-
- if (!fromleaf)
+ frame. This macro will set FROMLEAF if NEXT_FRAME is a frameless
+ function invocation. */
+ if (next_frame->next == NULL)
+ /* FIXME: 2002-11-09: Frameless functions can occure anywhere in
+ the frame chain, not just the inner most frame! The generic,
+ per-architecture, frame code should handle this and the below
+ should simply be removed. */
+ fromleaf = FRAMELESS_FUNCTION_INVOCATION (next_frame);
+ else
+ fromleaf = 0;
+
+ if (fromleaf)
+ /* A frameless inner-most frame. The `FP' (which isn't an
+ architecture frame-pointer register!) of the caller is the same
+ as the callee. */
+ /* FIXME: 2002-11-09: There isn't any reason to special case this
+ edge condition. Instead the per-architecture code should hande
+ it locally. */
+ address = FRAME_FP (next_frame);
+ else
{
/* Two macros defined in tm.h specify the machine-dependent
actions to be performed here.
+
First, get the frame's chain-pointer.
+
If that is zero, the frame is the outermost frame or a leaf
called by the outermost frame. This means that if start
calls main without a frame, we'll return 0 (which is fine
if (address == 0)
return 0;
+ /* Create an initially zero previous frame. */
prev = (struct frame_info *)
obstack_alloc (&frame_cache_obstack,
sizeof (struct frame_info));
-
- /* Zero all fields by default. */
memset (prev, 0, sizeof (struct frame_info));
- if (next_frame)
- next_frame->prev = prev;
+ /* Link it in. */
+ next_frame->prev = prev;
prev->next = next_frame;
prev->frame = address;
prev->level = next_frame->level + 1;
-/* This change should not be needed, FIXME! We should
- determine whether any targets *need* INIT_FRAME_PC to happen
- after INIT_EXTRA_FRAME_INFO and come up with a simple way to
- express what goes on here.
-
- INIT_EXTRA_FRAME_INFO is called from two places: create_new_frame
- (where the PC is already set up) and here (where it isn't).
- INIT_FRAME_PC is only called from here, always after
- INIT_EXTRA_FRAME_INFO.
-
- The catch is the MIPS, where INIT_EXTRA_FRAME_INFO requires the PC
- value (which hasn't been set yet). Some other machines appear to
- require INIT_EXTRA_FRAME_INFO before they can do INIT_FRAME_PC. Phoo.
-
- We shouldn't need INIT_FRAME_PC_FIRST to add more complication to
- an already overcomplicated part of GDB. gnu@cygnus.com, 15Sep92.
-
- Assuming that some machines need INIT_FRAME_PC after
- INIT_EXTRA_FRAME_INFO, one possible scheme:
-
- SETUP_INNERMOST_FRAME()
- Default version is just create_new_frame (read_fp ()),
- read_pc ()). Machines with extra frame info would do that (or the
- local equivalent) and then set the extra fields.
- SETUP_ARBITRARY_FRAME(argc, argv)
- Only change here is that create_new_frame would no longer init extra
- frame info; SETUP_ARBITRARY_FRAME would have to do that.
- INIT_PREV_FRAME(fromleaf, prev)
- Replace INIT_EXTRA_FRAME_INFO and INIT_FRAME_PC. This should
- also return a flag saying whether to keep the new frame, or
- whether to discard it, because on some machines (e.g. mips) it
- is really awkward to have FRAME_CHAIN_VALID called *before*
- INIT_EXTRA_FRAME_INFO (there is no good way to get information
- deduced in FRAME_CHAIN_VALID into the extra fields of the new frame).
- std_frame_pc(fromleaf, prev)
- This is the default setting for INIT_PREV_FRAME. It just does what
- the default INIT_FRAME_PC does. Some machines will call it from
- INIT_PREV_FRAME (either at the beginning, the end, or in the middle).
- Some machines won't use it.
- kingdon@cygnus.com, 13Apr93, 31Jan94, 14Dec94. */
+ /* This change should not be needed, FIXME! We should determine
+ whether any targets *need* INIT_FRAME_PC to happen after
+ INIT_EXTRA_FRAME_INFO and come up with a simple way to express
+ what goes on here.
+
+ INIT_EXTRA_FRAME_INFO is called from two places: create_new_frame
+ (where the PC is already set up) and here (where it isn't).
+ INIT_FRAME_PC is only called from here, always after
+ INIT_EXTRA_FRAME_INFO.
+
+ The catch is the MIPS, where INIT_EXTRA_FRAME_INFO requires the
+ PC value (which hasn't been set yet). Some other machines appear
+ to require INIT_EXTRA_FRAME_INFO before they can do
+ INIT_FRAME_PC. Phoo.
+
+ We shouldn't need INIT_FRAME_PC_FIRST to add more complication to
+ an already overcomplicated part of GDB. gnu@cygnus.com, 15Sep92.
+
+ Assuming that some machines need INIT_FRAME_PC after
+ INIT_EXTRA_FRAME_INFO, one possible scheme:
+
+ SETUP_INNERMOST_FRAME(): Default version is just create_new_frame
+ (read_fp ()), read_pc ()). Machines with extra frame info would
+ do that (or the local equivalent) and then set the extra fields.
+
+ SETUP_ARBITRARY_FRAME(argc, argv): Only change here is that
+ create_new_frame would no longer init extra frame info;
+ SETUP_ARBITRARY_FRAME would have to do that.
+
+ INIT_PREV_FRAME(fromleaf, prev) Replace INIT_EXTRA_FRAME_INFO and
+ INIT_FRAME_PC. This should also return a flag saying whether to
+ keep the new frame, or whether to discard it, because on some
+ machines (e.g. mips) it is really awkward to have
+ FRAME_CHAIN_VALID called *before* INIT_EXTRA_FRAME_INFO (there is
+ no good way to get information deduced in FRAME_CHAIN_VALID into
+ the extra fields of the new frame). std_frame_pc(fromleaf, prev)
+
+ This is the default setting for INIT_PREV_FRAME. It just does
+ what the default INIT_FRAME_PC does. Some machines will call it
+ from INIT_PREV_FRAME (either at the beginning, the end, or in the
+ middle). Some machines won't use it.
+
+ kingdon@cygnus.com, 13Apr93, 31Jan94, 14Dec94. */
+
+ /* NOTE: cagney/2002-11-09: Just ignore the above! There is no
+ reason for things to be this complicated.
+
+ The trick is to assume that there is always a frame. Instead of
+ special casing the inner-most frame, create fake frame
+ (containing the hardware registers) that is inner to the
+ user-visible inner-most frame (...) and then unwind from that.
+ That way architecture code can use use the standard
+ frame_XX_unwind() functions and not differentiate between the
+ inner most and any other case.
+
+ Since there is always a frame to unwind from, there is always
+ somewhere (NEXT_FRAME) to store all the info needed to construct
+ a new (previous) frame without having to first create it. This
+ means that the convolution below - needing to carefully order a
+ frame's initialization - isn't needed.
+
+ The irony here though, is that FRAME_CHAIN(), at least for a more
+ up-to-date architecture, always calls FRAME_SAVED_PC(), and
+ FRAME_SAVED_PC() computes the PC but without first needing the
+ frame! Instead of the convolution below, we could have simply
+ called FRAME_SAVED_PC() and been done with it! Note that
+ FRAME_SAVED_PC() is being superseed by frame_pc_unwind() and that
+ function does have somewhere to cache that PC value. */
INIT_FRAME_PC_FIRST (fromleaf, prev);
INIT_EXTRA_FRAME_INFO (fromleaf, prev);
/* This entry is in the frame queue now, which is good since
- FRAME_SAVED_PC may use that queue to figure out its value
- (see tm-sparc.h). We want the pc saved in the inferior frame. */
+ FRAME_SAVED_PC may use that queue to figure out its value (see
+ tm-sparc.h). We want the pc saved in the inferior frame. */
INIT_FRAME_PC (fromleaf, prev);
- /* If ->frame and ->pc are unchanged, we are in the process of getting
- ourselves into an infinite backtrace. Some architectures check this
- in FRAME_CHAIN or thereabouts, but it seems like there is no reason
- this can't be an architecture-independent check. */
- if (next_frame != NULL)
+ /* If ->frame and ->pc are unchanged, we are in the process of
+ getting ourselves into an infinite backtrace. Some architectures
+ check this in FRAME_CHAIN or thereabouts, but it seems like there
+ is no reason this can't be an architecture-independent check. */
+ if (prev->frame == next_frame->frame
+ && prev->pc == next_frame->pc)
{
- if (prev->frame == next_frame->frame
- && prev->pc == next_frame->pc)
- {
- next_frame->prev = NULL;
- obstack_free (&frame_cache_obstack, prev);
- return NULL;
- }
+ next_frame->prev = NULL;
+ obstack_free (&frame_cache_obstack, prev);
+ return NULL;
}
/* Initialize the code used to unwind the frame PREV based on the PC
projects / binutils-gdb.git / commitdiff