Introduce thread-safe way to handle SIGSEGV
The gdb demangler installs a SIGSEGV handler in order to protect gdb
from demangler bugs. However, this is not thread-safe, as signal
handlers are global to the process.
This patch changes gdb to always install a global SIGSEGV handler, and
then lets threads indicate their interest in handling the signal by
setting a thread-local variable.
This patch then arranges for the demangler code to use this; being
sure to arrange for calls to warning and the like to be done on the
main thread.
One thing I wondered while writing this patch is if there are any
systems that do not have "sigaction". If gdb could assume this, it
would simplify this code.
gdb/ChangeLog
2019-11-26 Tom Tromey <tom@tromey.com>
* event-top.h (thread_local_segv_handler): Declare.
* event-top.c (thread_local_segv_handler): New global.
(install_handle_sigsegv, handle_sigsegv): New functions.
(async_init_signals): Install SIGSEGV handler.
* cp-support.c (gdb_demangle_jmp_buf): Change type. Now
thread-local.
(report_failed_demangle): New function.
(gdb_demangle): Make core_dump_allowed atomic. Remove signal
handler-setting code, instead use segv_handler. Run warning code
on main thread.
Change-Id: Ic832bbb033b64744e4b44f14b41db7e4168ce427
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