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0703599a49
On decr_pc_after_break targets, GDB adjusts the PC incorrectly if a background single-step stops somewhere where PC-$decr_pc has a breakpoint, and the thread that finishes the step is not the current thread, like: ADDR1 nop <-- breakpoint here ADDR2 jmp PC IOW, say thread A is stepping ADDR2's line in the background (an infinite loop), and the user switches focus to thread B. GDB's adjust_pc_after_break logic confuses the single-step stop of thread A for a hit of the breakpoint at ADDR1, and thus adjusts thread A's PC to point at ADDR1 when it should not, and reports a breakpoint hit, when thread A did not execute the instruction at ADDR1 at all. The test added by this patch exercises exactly that. I can't find any reason we'd need the "thread to be examined is still the current thread" condition in adjust_pc_after_break, at least nowadays; it might have made sense in the past. Best just remove it, and rely on currently_stepping(). Here's the test's log of a run with an unpatched GDB: 35 while (1); (gdb) PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: next over nop next& (gdb) PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: next& over inf loop thread 1 [Switching to thread 1 (Thread 0x7ffff7fc2740 (LWP 29027))](running) (gdb) PASS: gdb.threads/step-bg-decr-pc-switch-thread.exp: switch to main thread Breakpoint 2, thread_function (arg=0x0) at ...src/gdb/testsuite/gdb.threads/step-bg-decr-pc-switch-thread.c:34 34 NOP; /* set breakpoint here */ FAIL: gdb.threads/step-bg-decr-pc-switch-thread.exp: no output while stepping gdb/ChangeLog: 2015-02-11 Pedro Alves <pedro@codesourcery.com> * infrun.c (adjust_pc_after_break): Don't adjust the PC just because the event thread is not the current thread. gdb/testsuite/ChangeLog: 2015-02-11 Pedro Alves <pedro@codesourcery.com> * gdb.threads/step-bg-decr-pc-switch-thread.c: New file. * gdb.threads/step-bg-decr-pc-switch-thread.exp: New file. |
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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.