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ecdc3a72c8
After commit 00431a78b28f ("Use thread_info and inferior pointers more
throughout"), following an exec can result in gdb crashing. On some
systems, this is visible with gdb.multi/multi-arch-exec.exp and
gdb.base/foll-exec-mode.exp. E.g.:
$ make check TESTS="gdb.multi/multi-arch-exec.exp gdb.base/foll-exec-mode.exp"
[snip]
FAIL: gdb.multi/multi-arch-exec.exp: first_arch=1: selected_thread=1: follow_exec_mode=new: continue across exec that changes architecture (GDB internal error)
ERROR: : spawn id exp10 not open
while executing
Running multi-arch-exec under Valgrind we easily spot the problem:
process 16305 is executing new program: ..../gdb.multi/multi-arch-exec/1-multi-arch-exec-hello
[New inferior 2 (process 0)]
[New process 16305]
==16129== Invalid read of size 8
==16129== at 0x7FA14D: get_thread_regcache(thread_info*) (regcache.c:399)
==16129== by 0x75E54B: handle_inferior_event_1(execution_control_state*) (infrun.c:5292)
==16129== by 0x75E82D: handle_inferior_event(execution_control_state*) (infrun.c:5382)
==16129== by 0x75BC6A: fetch_inferior_event(void*) (infrun.c:3918)
==16129== by 0x748DA3: inferior_event_handler(inferior_event_type, void*) (inf-loop.c:43)
==16129== by 0x464B5D: handle_target_event(int, void*) (linux-nat.c:4359)
==16129== by 0x7047E0: handle_file_event(file_handler*, int) (event-loop.c:733)
==16129== by 0x704D83: gdb_wait_for_event(int) (event-loop.c:859)
==16129== by 0x703BF6: gdb_do_one_event() (event-loop.c:322)
==16129== by 0x703CA2: start_event_loop() (event-loop.c:371)
==16129== by 0x791D95: captured_command_loop() (main.c:330)
==16129== by 0x79311C: captured_main(void*) (main.c:1157)
==16129== Address 0x15a5bad0 is 32 bytes inside a block of size 600 free'd
==16129== at 0x4C2E1E8: operator delete(void*) (vg_replace_malloc.c:576)
==16129== by 0x8A15D0: delete_thread_1(thread_info*, bool) (thread.c:465)
==16129== by 0x8A15FA: delete_thread(thread_info*) (thread.c:476)
==16129== by 0x8A0D43: add_thread_silent(ptid_t) (thread.c:291)
==16129== by 0x8A0DF0: add_thread_with_info(ptid_t, private_thread_info*) (thread.c:317)
==16129== by 0x8A0E79: add_thread(ptid_t) (thread.c:331)
==16129== by 0x75764C: follow_exec(ptid_t, char*) (infrun.c:1233)
==16129== by 0x75E534: handle_inferior_event_1(execution_control_state*) (infrun.c:5290)
==16129== by 0x75E82D: handle_inferior_event(execution_control_state*) (infrun.c:5382)
==16129== by 0x75BC6A: fetch_inferior_event(void*) (infrun.c:3918)
==16129== by 0x748DA3: inferior_event_handler(inferior_event_type, void*) (inf-loop.c:43)
==16129== by 0x464B5D: handle_target_event(int, void*) (linux-nat.c:4359)
The problem is that handle_inferior_event_1 is reading the stop_pc off
of a thread that was deleted by follow_exec. Before commit
00431a78b28f, we didn't crash because we were passing down a ptid to
get_thread_regcache instead of ecs->event_thread.
Fix this by simply moving the stop_pc reading until after
ecs->event_thread is refreshed.
gdb/ChangeLog:
2018-06-28 Pedro Alves <palves@redhat.com>
* infrun.c (handle_inferior_event_1) <TARGET_WAITKIND_EXECD>:
Moving fetching stop_pc until after ecs->event_thread is refreshed.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.