8bcb520897
Supply default gdbarch methods for gdbarch_dummy_id, gdbarch_unwind_pc, and gdbarch_unwind_sp. This patch doesn't actually convert any targets to use these methods, and so, there will be no user visible changes after this commit. The implementations for default_dummy_id and default_unwind_sp are fairly straight forward, these just take on the pattern used by most targets. Once these default methods are in place then most targets will be able to switch over. The implementation for default_unwind_pc is also fairly straight forward, but maybe needs some explanation. This patch has gone through a number of iterations: https://sourceware.org/ml/gdb-patches/2018-03/msg00165.html https://sourceware.org/ml/gdb-patches/2018-03/msg00306.html https://sourceware.org/ml/gdb-patches/2018-06/msg00090.html https://sourceware.org/ml/gdb-patches/2018-09/msg00127.html and the implementation of default_unwind_pc has changed over this time. Originally, I took an implementation like this: CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame) { int pc_regnum = gdbarch_pc_regnum (gdbarch); return frame_unwind_register_unsigned (next_frame, pc_regnum); } This is basically a clone of default_unwind_sp, but using $pc. It was pointed out that we could potentially do better, and in version 2 the implementation became: CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame) { struct type *type; int pc_regnum; CORE_ADDR addr; struct value *value; pc_regnum = gdbarch_pc_regnum (gdbarch); value = frame_unwind_register_value (next_frame, pc_regnum); type = builtin_type (gdbarch)->builtin_func_ptr; addr = extract_typed_address (value_contents_all (value), type); addr = gdbarch_addr_bits_remove (gdbarch, addr); release_value (value); value_free (value); return addr; } The idea was to try split out some of the steps of unwinding the $pc, steps that are on some (or many) targets no-ops, and so allow targets that do override these methods, to make use of default_unwind_pc. This implementation remained in place for version 2, 3, and 4. However, I realised that I'd made a mistake, most targets simply use frame_unwind_register_unsigned to unwind the $pc, and this throws an error if the register value is optimized out or unavailable. My new proposed implementation doesn't do this, I was going to end up breaking many targets. I considered duplicating the code from frame_unwind_register_unsigned that throws the errors into my new default_unwind_pc, however, this felt really overly complex. So, what I instead went with was to simply revert back to using frame_unwind_register_unsigned. Almost all existing targets already use this. Some of the ones that don't can be converted to, which means almost all targets could end up using the default. One addition I have made over the version 1 implementation is to add a call to gdbarch_addr_bits_remove. For most targets this is a no-op, but for a handful, having this call in place will mean that they can use the default method. After all this, the new default_unwind_pc now looks like this: CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame) { int pc_regnum = gdbarch_pc_regnum (gdbarch); CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum); pc = gdbarch_addr_bits_remove (gdbarch, pc); return pc; } gdb/ChangeLog: * gdb/dummy-frame.c (default_dummy_id): Defined new function. * gdb/dummy-frame.h (default_dummy_id): Declare new function. * gdb/frame-unwind.c (default_unwind_pc): Define new function. (default_unwind_sp): Define new function. * gdb/frame-unwind.h (default_unwind_pc): Declare new function. (default_unwind_sp): Declare new function. * gdb/frame.c (frame_unwind_pc): Assume gdbarch_unwind_pc is available. (get_frame_sp): Assume that gdbarch_unwind_sp is available. * gdb/gdbarch.c: Regenerate. * gdb/gdbarch.h: Regenerate. * gdb/gdbarch.sh: Update definition of dummy_id, unwind_pc, and unwind_sp. Add additional header files to be included in generated file.
236 lines
9.1 KiB
C
236 lines
9.1 KiB
C
/* Definitions for a frame unwinder, for GDB, the GNU debugger.
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Copyright (C) 2003-2018 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#if !defined (FRAME_UNWIND_H)
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#define FRAME_UNWIND_H 1
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struct frame_data;
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struct frame_info;
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struct frame_id;
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struct frame_unwind;
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struct gdbarch;
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struct regcache;
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struct value;
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#include "frame.h" /* For enum frame_type. */
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/* The following unwind functions assume a chain of frames forming the
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sequence: (outer) prev <-> this <-> next (inner). All the
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functions are called with this frame's `struct frame_info' and
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prologue cache.
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THIS frame's register values can be obtained by unwinding NEXT
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frame's registers (a recursive operation).
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THIS frame's prologue cache can be used to cache information such
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as where this frame's prologue stores the previous frame's
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registers. */
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/* Given THIS frame, take a whiff of its registers (namely
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the PC and attributes) and if SELF is the applicable unwinder,
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return non-zero. Possibly also initialize THIS_PROLOGUE_CACHE; but
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only if returning 1. Initializing THIS_PROLOGUE_CACHE in other
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cases (0 return) is invalid. In case of exception, the caller has
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to set *THIS_PROLOGUE_CACHE to NULL. */
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typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
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struct frame_info *this_frame,
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void **this_prologue_cache);
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typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype)
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(struct frame_info *this_frame, void **this_prologue_cache);
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/* A default frame sniffer which always accepts the frame. Used by
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fallback prologue unwinders. */
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int default_frame_sniffer (const struct frame_unwind *self,
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struct frame_info *this_frame,
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void **this_prologue_cache);
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/* A default stop_reason callback which always claims the frame is
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unwindable. */
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enum unwind_stop_reason
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default_frame_unwind_stop_reason (struct frame_info *this_frame,
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void **this_cache);
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/* A default unwind_pc callback that simply unwinds the register identified
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by GDBARCH_PC_REGNUM. */
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extern CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch,
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struct frame_info *next_frame);
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/* A default unwind_sp callback that simply unwinds the register identified
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by GDBARCH_SP_REGNUM. */
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extern CORE_ADDR default_unwind_sp (struct gdbarch *gdbarch,
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struct frame_info *next_frame);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and through it the NEXT frame's register unwind
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method, to determine the frame ID of THIS frame.
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A frame ID provides an invariant that can be used to re-identify an
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instance of a frame. It is a combination of the frame's `base' and
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the frame's function's code address.
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Traditionally, THIS frame's ID was determined by examining THIS
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frame's function's prologue, and identifying the register/offset
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used as THIS frame's base.
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Example: An examination of THIS frame's prologue reveals that, on
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entry, it saves the PC(+12), SP(+8), and R1(+4) registers
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(decrementing the SP by 12). Consequently, the frame ID's base can
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be determined by adding 12 to the THIS frame's stack-pointer, and
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the value of THIS frame's SP can be obtained by unwinding the NEXT
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frame's SP.
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THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
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with the other unwind methods. Memory for that cache should be
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allocated using FRAME_OBSTACK_ZALLOC(). */
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typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
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void **this_prologue_cache,
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struct frame_id *this_id);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and implicitly the NEXT frame's register unwind
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method, to unwind THIS frame's registers (returning the value of
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the specified register REGNUM in the previous frame).
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Traditionally, THIS frame's registers were unwound by examining
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THIS frame's function's prologue and identifying which registers
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that prolog code saved on the stack.
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Example: An examination of THIS frame's prologue reveals that, on
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entry, it saves the PC(+12), SP(+8), and R1(+4) registers
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(decrementing the SP by 12). Consequently, the value of the PC
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register in the previous frame is found in memory at SP+12, and
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THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
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This function takes THIS_FRAME as an argument. It can find the
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values of registers in THIS frame by calling get_frame_register
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(THIS_FRAME), and reinvoke itself to find other registers in the
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PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
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The result is a GDB value object describing the register value. It
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may be a lazy reference to memory, a lazy reference to the value of
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a register in THIS frame, or a non-lvalue.
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THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
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with the other unwind methods. Memory for that cache should be
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allocated using FRAME_OBSTACK_ZALLOC(). */
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typedef struct value * (frame_prev_register_ftype)
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(struct frame_info *this_frame, void **this_prologue_cache,
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int regnum);
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/* Deallocate extra memory associated with the frame cache if any. */
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typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
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void *this_cache);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and implicitly the NEXT frame's register unwind
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method, return PREV frame's architecture. */
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typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
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void **this_prologue_cache);
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struct frame_unwind
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{
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/* The frame's type. Should this instead be a collection of
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predicates that test the frame for various attributes? */
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enum frame_type type;
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/* Should an attribute indicating the frame's address-in-block go
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here? */
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frame_unwind_stop_reason_ftype *stop_reason;
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frame_this_id_ftype *this_id;
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frame_prev_register_ftype *prev_register;
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const struct frame_data *unwind_data;
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frame_sniffer_ftype *sniffer;
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frame_dealloc_cache_ftype *dealloc_cache;
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frame_prev_arch_ftype *prev_arch;
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};
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/* Register a frame unwinder, _prepending_ it to the front of the
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search list (so it is sniffed before previously registered
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unwinders). By using a prepend, later calls can install unwinders
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that override earlier calls. This allows, for instance, an OSABI
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to install a more specific sigtramp unwinder that overrides the
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traditional brute-force unwinder. */
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extern void frame_unwind_prepend_unwinder (struct gdbarch *,
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const struct frame_unwind *);
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/* Add a frame sniffer to the list. The predicates are polled in the
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order that they are appended. The initial list contains the dummy
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frame sniffer. */
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extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
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const struct frame_unwind *unwinder);
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/* Iterate through sniffers for THIS_FRAME frame until one returns with an
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unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set
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by this function. Possibly initialize THIS_CACHE. */
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extern void frame_unwind_find_by_frame (struct frame_info *this_frame,
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void **this_cache);
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/* Helper functions for value-based register unwinding. These return
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a (possibly lazy) value of the appropriate type. */
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/* Return a value which indicates that FRAME did not save REGNUM. */
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struct value *frame_unwind_got_optimized (struct frame_info *frame,
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int regnum);
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/* Return a value which indicates that FRAME copied REGNUM into
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register NEW_REGNUM. */
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struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
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int new_regnum);
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/* Return a value which indicates that FRAME saved REGNUM in memory at
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ADDR. */
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struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
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CORE_ADDR addr);
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/* Return a value which indicates that FRAME's saved version of
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REGNUM has a known constant (computed) value of VAL. */
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struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
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ULONGEST val);
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/* Return a value which indicates that FRAME's saved version of
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REGNUM has a known constant (computed) value which is stored
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inside BUF. */
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struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
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gdb_byte *buf);
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/* Return a value which indicates that FRAME's saved version of REGNUM
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has a known constant (computed) value of ADDR. Convert the
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CORE_ADDR to a target address if necessary. */
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struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
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CORE_ADDR addr);
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#endif
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