[Converted from Gnats 1329] Should there be a command to explicitly enable/disable specific unwinders? Release: unknown
The master branch has been updated by Andrew Burgess <aburgess@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3c3bb0580be0027a1c7187b78c747af74dcfa884 commit 3c3bb0580be0027a1c7187b78c747af74dcfa884 Author: Andrew Burgess <andrew.burgess@embecosm.com> Date: Fri Jul 13 12:01:16 2018 +0100 gdb: Add switch to disable DWARF stack unwinders Add a maintenance command to disable the DWARF stack unwinders. Normal users would not need this feature, but it is useful to allow extended testing of fallback stack unwinding strategies, for example, prologue scanners. This is a partial implementation of the idea discussed in pr gdb/8434, which talks about a generic ability to disable any frame unwinder. Being able to arbitrarily disable any frame unwinder would be a more complex patch, and I was unsure how useful such a feature would really be, however, I can see (and have) a real need to disable DWARF unwinders. That's why this patch only targets that specific set of unwinders. If in the future we find ourselves adding more switches to disable different unwinders, then we should probably move to a more generic solution, and remove this patch. gdb/ChangeLog: * dwarf2-frame-tailcall.c (tailcall_frame_sniffer): Exit early if DWARF unwinders are disabled. * dwarf2-frame.c: Add dwarf2read.h include. (dwarf2_frame_sniffer): Exit early if DWARF unwinders are disabled. (dwarf2_frame_unwinders_enabled_p): Define. (show_dwarf_unwinders_enabled_p): New function. (_initialize_dwarf2_frame): Register switch to control DWARF unwinder use. * dwarf2-frame.h (dwarf2_frame_unwinders_enabled_p): Declare. * dwarf2read.c (set_dwarf_cmdlist): Remove static keyword. (show_dwarf_cmdlist): Remove static keyword. * dwarf2read.h (set_dwarf_cmdlist): Declare. (show_dwarf_cmdlist): Declare. * NEWS: Document new feature. gdb/doc/ChangeLog: * gdb.texinfo (Maintenance Commands): Add description of maintenance command to control dwarf unwinders. gdb/testsuite/ChangeLog: * gdb.base/maint.exp: Add check that dwarf unwinders control flag is visible.
The master branch has been updated by Guinevere Larsen <guinevere@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b49f56d0aa0bcd8d73e87e6e17ff4fb0efa4c090 commit b49f56d0aa0bcd8d73e87e6e17ff4fb0efa4c090 Author: Guinevere Larsen <guinevere@redhat.com> Date: Thu Mar 14 16:14:28 2024 +0100 gdb: introduce ability to disable frame unwinders Sometimes, in the GDB testsuite, we want to test the ability of specific unwinders to handle some piece of code. Usually this is done by trying to outsmart GDB, or by coercing the compiler to remove information that GDB would rely on. Both approaches have problems as GDB gets smarter with time, and that compilers might differ in version and behavior, or simply introduce new useful information. This was requested back in 2003 in PR backtrace/8434. To improve our ability to thoroughly test GDB, this patch introduces a new maintenance command that allows a user to disable some unwinders, based on either the name of the unwinder or on its class. With this change, it will now be possible for GDB to not find any frame unwinders for a given frame, which would previously cause GDB to assert. GDB will now check if any frame unwinder has been disabled, and if some has, it will just error out instead of asserting. Unwinders can be disabled or re-enabled in 3 different ways: * Disabling/enabling all at once (using '-all'). * By specifying an unwinder class to be disabled (option '-class'). * By specifying the name of an unwinder (option '-name'). If you give no options to the command, GDB assumes the input is an unwinder class. '-class' would make no difference if used, is just here for completeness. This command is meant to be used once the inferior is already at the desired location for the test. An example session would be: (gdb) start Temporary breakpoint 1, main () at omp.c:17 17 func(); (gdb) maint frame-unwinder disable ARCH (gdb) bt \#0 main () at omp.c:17 (gdb) maint frame-unwinder enable ARCH (gdb) cont Continuing. This commit is a more generic version of commit 3c3bb0580be0, and so, based on the final paragraph of the commit message: gdb: Add switch to disable DWARF stack unwinders <...> If in the future we find ourselves adding more switches to disable different unwinders, then we should probably move to a more generic solution, and remove this patch. this patch also reverts 3c3bb0580be0 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=8434 Co-Authored-By: Andrew Burgess <aburgess@redhat.com> Reviewed-By: Eli Zaretskii <eliz@gnu.org> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org> Approved-By: Andrew Burgess <aburgess@redhat.com> temp adding completion