b9f437de50
Consider the case of the user doing "step" in thread 2, while thread 1 had previously stopped for a breakpoint. In order to make progress, GDB makes thread 1 step over its breakpoint first (with all other threads stopped), and once that is over, thread 2 then starts stepping (with thread 1 and all others running free, by default). If GDB didn't do that, thread 1 would just trip on the same breakpoint immediately again. This is what the prepare_to_proceed / deferred_step_ptid code is all about. However, deferred_step_ptid code resumes the target with: resume (1, GDB_SIGNAL_0); prepare_to_wait (ecs); return; Recall we were just stepping over a breakpoint when we get here. That means that _nothing_ had installed breakpoints yet! If there's another breakpoint just after the breakpoint that was just stepped, we'll miss it. The fix for that would be to use keep_going instead. However, there are more problems. What if the instruction that was just single-stepped triggers a watchpoint? Currently, GDB just happily resumes the thread, losing that too... Missed watchpoints will need yet further fixes, but we should keep those in mind. So the fix must be to let the trap fall through the regular bpstat handling, and only if no breakpoint, watchpoint, etc. claims the trap, shall we switch back to the stepped thread. Now, nowadays, we have code at the tail end of trap handling that does exactly that -- switch back to the stepped thread (switch_back_to_the_stepped_thread). So the deferred_step_ptid code is just standing in the way, and can simply be eliminated, fixing bugs in the process. Sweet. The comment about spurious "Switching to ..." made me pause, but is actually stale nowadays. That isn't needed anymore. previous_inferior_ptid used to be re-set at each (internal) event, but now it's only touched in proceed and normal stop. The two tests added by this patch fail without the fix. Tested on x86_64 Fedora 17 (also against my software single-stepping on x86 branch). gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * infrun.c (previous_inferior_ptid): Adjust comment. (deferred_step_ptid): Delete. (infrun_thread_ptid_changed, prepare_to_proceed) (init_wait_for_inferior): Adjust. (handle_signal_stop): Delete deferred_step_ptid handling. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-lands-on-breakpoint.c: New file. * gdb.threads/step-over-lands-on-breakpoint.exp: New file. |
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bfd | ||
binutils | ||
config | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
.cvsignore | ||
.gitignore | ||
ChangeLog | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
COPYING | ||
COPYING3 | ||
COPYING3.LIB | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
lt~obsolete.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release | ||
symlink-tree | ||
ylwrap |
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.