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98c59b527b
The patch makes GDB do exec-file-mismatch validation by comparing build IDs instead of the current method of comparing filenames. Currently, the exec-file-mismatch feature simply compares filenames to decide whether the exec file loaded in gdb and the exec file the target reports is running match. This causes false positives when remote debugging, because it'll often be the case that the paths in the host and the target won't match. And of course misses the case of the files having the same name but being actually different files (e.g., different builds). This also broke many testcases when running against gdbserver, causing tests to be skipped like (here native-extended-gdbserver): (gdb) run Starting program: /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink-filelink warning: Mismatch between current exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink-filelink and automatically determined exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink exec-file-mismatch handling is currently "ask" Load new symbol table from "/home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink"? (y or n) UNTESTED: gdb.base/argv0-symlink.exp: could not run to main or to fail like (here native-gdbserver): (gdb) spawn /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/../../gdbserver/gdbserver --once localhost:2346 /home/pedro/gdb/binutils-gdb/build/gdb/te stsuite/outputs/gdb.btrace/buffer-size/skip_btrace_tests-19968.x Process /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.btrace/buffer-size/skip_btrace_tests-19968.x created; pid = 20040 Listening on port 2346 target remote localhost:2346 Remote debugging using localhost:2346 warning: Mismatch between current exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/temp/19968/skip_btrace_tests-19968.x and automatically determined exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.btrace/buffer-size/skip_btrace_tests-19968.x exec-file-mismatch handling is currently "ask" Load new symbol table from "/home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.btrace/buffer-size/skip_btrace_tests-19968.x"? (y or n) Quit (gdb) UNSUPPORTED: gdb.btrace/buffer-size.exp: target does not support record-btrace The former case is about GDB not realizing the two files are the same, because one of the them is a symlink to the other. The latter case is about GDB realizing that one file is a copy of the other. Over the years, the toolchain has settled on build ID matching being the canonical method to match core dumps to executables, and executables with no debug info to their debug info. This patch makes us use build IDs to match the running image of a binary with its version loaded in gdb, which may or may not have debug info. This is very much like the core dump/executable matching. The change to gdb_bfd_open is necessary to get rid of the "transfers from remote targets can be slow" warning when we open the remote file to read its build ID: (gdb) r Starting program: /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/break/break Reading /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink from remote target... warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: Mismatch between current exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/break/break and automatically determined exec-file /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink exec-file-mismatch handling is currently "ask" Load new symbol table from "/home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.base/argv0-symlink/argv0-symlink"? (y or n) While trying this out, I was worried that bfd would read a lot of stuff from the binary in order to extract the build ID, making it potentially slow, but turns out we don't read all that much. Maybe a couple hundred bytes, and most of it seemingly is the read-ahead cache. So I'm not worried about that. Otherwise I'd consider whether a new qXfer:buildid:read would be better. But I'm happy that we seemingly don't need to worry about it. gdb/ChangeLog: 2020-05-19 Pedro Alves <palves@redhat.com> * NEWS (set exec-file-mismatch): Adjust entry. * exec.c: Include "build-id.h". (validate_exec_file): Try to match build IDs instead of filenames. * gdb_bfd.c (struct gdb_bfd_open_closure): New. (gdb_bfd_iovec_fileio_open): Adjust to use gdb_bfd_open_closure and pass down 'warn_if_slow'. (gdb_bfd_open): Add 'warn_if_slow' parameter. Use gdb_bfd_open_closure to pass it down. * gdb_bfd.h (gdb_bfd_open): Add 'warn_if_slow' parameter. gdb/doc/ChangeLog: 2020-05-19 Pedro Alves <palves@redhat.com> * gdb.texinfo (Attach): Update exec-file-mismatch description to mention build IDs. (Separate Debug Files): Add "build id" anchor.
197 lines
7.1 KiB
C
197 lines
7.1 KiB
C
/* Definitions for BFD wrappers used by GDB.
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Copyright (C) 2011-2020 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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#ifndef GDB_BFD_H
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#define GDB_BFD_H
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#include "registry.h"
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#include "gdbsupport/byte-vector.h"
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#include "gdbsupport/gdb_ref_ptr.h"
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DECLARE_REGISTRY (bfd);
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/* If supplied a path starting with this sequence, gdb_bfd_open will
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open BFDs using target fileio operations. */
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#define TARGET_SYSROOT_PREFIX "target:"
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/* Returns nonzero if NAME starts with TARGET_SYSROOT_PREFIX, zero
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otherwise. */
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int is_target_filename (const char *name);
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/* Returns nonzero if the filename associated with ABFD starts with
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TARGET_SYSROOT_PREFIX, zero otherwise. */
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int gdb_bfd_has_target_filename (struct bfd *abfd);
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/* Increment the reference count of ABFD. It is fine for ABFD to be
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NULL; in this case the function does nothing. */
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void gdb_bfd_ref (struct bfd *abfd);
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/* Decrement the reference count of ABFD. If this is the last
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reference, ABFD will be freed. If ABFD is NULL, this function does
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nothing. */
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void gdb_bfd_unref (struct bfd *abfd);
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/* A policy class for gdb::ref_ptr for BFD reference counting. */
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struct gdb_bfd_ref_policy
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{
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static void incref (struct bfd *abfd)
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{
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gdb_bfd_ref (abfd);
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}
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static void decref (struct bfd *abfd)
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{
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gdb_bfd_unref (abfd);
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}
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};
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/* A gdb::ref_ptr that has been specialized for BFD objects. */
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typedef gdb::ref_ptr<struct bfd, gdb_bfd_ref_policy> gdb_bfd_ref_ptr;
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/* Open a read-only (FOPEN_RB) BFD given arguments like bfd_fopen.
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If NAME starts with TARGET_SYSROOT_PREFIX then the BFD will be
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opened using target fileio operations if necessary. Returns NULL
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on error. On success, returns a new reference to the BFD. BFDs
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returned by this call are shared among all callers opening the same
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file. If FD is not -1, then after this call it is owned by BFD.
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If the BFD was not accessed using target fileio operations then the
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filename associated with the BFD and accessible with
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bfd_get_filename will not be exactly NAME but rather NAME with
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TARGET_SYSROOT_PREFIX stripped. If WARN_IF_SLOW is true, print a
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warning message if the file is being accessed over a link that may
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be slow. */
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gdb_bfd_ref_ptr gdb_bfd_open (const char *name, const char *target,
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int fd = -1, bool warn_if_slow = true);
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/* Mark the CHILD BFD as being a member of PARENT. Also, increment
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the reference count of CHILD. Calling this function ensures that
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as along as CHILD remains alive, PARENT will as well. Both CHILD
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and PARENT must be non-NULL. This can be called more than once
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with the same arguments; but it is not allowed to call it for a
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single CHILD with different values for PARENT. */
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void gdb_bfd_mark_parent (bfd *child, bfd *parent);
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/* Mark INCLUDEE as being included by INCLUDER.
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This is used to associate the life time of INCLUDEE with INCLUDER.
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For example, with Fission, one file can refer to debug info in another
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file, and internal tables we build for the main file (INCLUDER) may refer
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to data contained in INCLUDEE. Therefore we want to keep INCLUDEE around
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at least as long as INCLUDER exists.
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Note that this is different than gdb_bfd_mark_parent because in our case
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lifetime tracking is based on the "parent" whereas in gdb_bfd_mark_parent
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lifetime tracking is based on the "child". Plus in our case INCLUDEE could
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have multiple different "parents". */
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void gdb_bfd_record_inclusion (bfd *includer, bfd *includee);
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/* Try to read or map the contents of the section SECT. If successful, the
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section data is returned and *SIZE is set to the size of the section data;
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this may not be the same as the size according to bfd_section_size if the
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section was compressed. The returned section data is associated with the BFD
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and will be destroyed when the BFD is destroyed. There is no other way to
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free it; for temporary uses of section data, see bfd_malloc_and_get_section.
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SECT may not have relocations. If there is an error reading the section,
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this issues a warning, sets *SIZE to 0, and returns NULL. */
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const gdb_byte *gdb_bfd_map_section (asection *section, bfd_size_type *size);
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/* Compute the CRC for ABFD. The CRC is used to find and verify
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separate debug files. When successful, this fills in *CRC_OUT and
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returns 1. Otherwise, this issues a warning and returns 0. */
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int gdb_bfd_crc (struct bfd *abfd, unsigned long *crc_out);
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/* A wrapper for bfd_fopen that initializes the gdb-specific reference
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count. */
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gdb_bfd_ref_ptr gdb_bfd_fopen (const char *, const char *, const char *, int);
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/* A wrapper for bfd_openr that initializes the gdb-specific reference
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count. */
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gdb_bfd_ref_ptr gdb_bfd_openr (const char *, const char *);
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/* A wrapper for bfd_openw that initializes the gdb-specific reference
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count. */
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gdb_bfd_ref_ptr gdb_bfd_openw (const char *, const char *);
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/* A wrapper for bfd_openr_iovec that initializes the gdb-specific
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reference count. */
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gdb_bfd_ref_ptr gdb_bfd_openr_iovec (const char *filename, const char *target,
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void *(*open_func) (struct bfd *nbfd,
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void *open_closure),
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void *open_closure,
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file_ptr (*pread_func) (struct bfd *nbfd,
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void *stream,
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void *buf,
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file_ptr nbytes,
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file_ptr offset),
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int (*close_func) (struct bfd *nbfd,
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void *stream),
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int (*stat_func) (struct bfd *abfd,
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void *stream,
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struct stat *sb));
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/* A wrapper for bfd_openr_next_archived_file that initializes the
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gdb-specific reference count. */
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gdb_bfd_ref_ptr gdb_bfd_openr_next_archived_file (bfd *archive, bfd *previous);
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/* Return the index of the BFD section SECTION. Ordinarily this is
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just the section's index, but for some special sections, like
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bfd_com_section_ptr, it will be a synthesized value. */
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int gdb_bfd_section_index (bfd *abfd, asection *section);
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/* Like bfd_count_sections, but include any possible global sections,
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like bfd_com_section_ptr. */
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int gdb_bfd_count_sections (bfd *abfd);
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/* Return true if any section requires relocations, false
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otherwise. */
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int gdb_bfd_requires_relocations (bfd *abfd);
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/* Alternative to bfd_get_full_section_contents that returns the section
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contents in *CONTENTS, instead of an allocated buffer.
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Return true on success, false otherwise. */
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bool gdb_bfd_get_full_section_contents (bfd *abfd, asection *section,
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gdb::byte_vector *contents);
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#endif /* GDB_BFD_H */
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