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2002-11-09 Andrew Cagney <ac131313@redhat.com>

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* frame.c (get_prev_frame): Cleanups.  Eliminate redundant tests
	for a NULL NEXT_FRAME.  Simplify fromleaf initialization.  Add
	more comments.  Zap dead code.
This commit is contained in:
Andrew Cagney 2002-11-09 17:45:17 +00:00
parent e71ecd70b2
commit 95adb866d7
2 changed files with 127 additions and 79 deletions
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6
gdb/ChangeLog
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@ -1,3 +1,9 @@
2002-11-09 Andrew Cagney <ac131313@redhat.com>
* frame.c (get_prev_frame): Cleanups. Eliminate redundant tests
for a NULL NEXT_FRAME. Simplify fromleaf initialization. Add
more comments. Zap dead code.
2002-11-09 Mark Kettenis <kettenis@gnu.org>
* infcmd.c (print_vector_info, print_float_info): Move code that

200
gdb/frame.c
View File

@ -717,31 +717,37 @@ get_prev_frame (struct frame_info *next_frame)
{
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
@ -751,20 +757,32 @@ get_prev_frame (struct frame_info *next_frame)
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);
}
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)
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
@ -791,59 +809,86 @@ get_prev_frame (struct frame_info *next_frame)
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.
/* 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.
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.
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.
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:
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. */
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);
@ -851,23 +896,20 @@ get_prev_frame (struct frame_info *next_frame)
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