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In 'set_breakpoint_condition', GDB resets the condition expressions
before parsing the condition input by the user. This leads to the
problem of losing the condition expressions if the new condition
does not parse successfully and is thus rejected.
For instance:
$ gdb ./test
Reading symbols from ./test...
(gdb) start
Temporary breakpoint 1 at 0x114e: file test.c, line 4.
Starting program: test
Temporary breakpoint 1, main () at test.c:4
4 int a = 10;
(gdb) break 5
Breakpoint 2 at 0x555555555155: file test.c, line 5.
Now define a condition that would evaluate to false. Next, attempt
to overwrite that with an invalid condition:
(gdb) cond 2 a == 999
(gdb) cond 2 gibberish
No symbol "gibberish" in current context.
(gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y 0x0000555555555155 in main at test.c:5
stop only if a == 999
It appears as if the bad condition is successfully rejected. But if we
resume the program, we see that we hit the breakpoint although the condition
would evaluate to false.
(gdb) continue
Continuing.
Breakpoint 2, main () at test.c:5
5 a = a + 1; /* break-here */
Fix the problem by not resetting the condition expressions before
parsing the condition input.
Suppose the fix is applied. A similar problem could occur if the
condition is valid, but has "junk" at the end. In this case, parsing
succeeds, but an error is raised immediately after. It is too late,
though; the condition expression is already updated.
For instance:
$ gdb ./test
Reading symbols from ./test...
(gdb) start
Temporary breakpoint 1 at 0x114e: file test.c, line 4.
Starting program: test
Temporary breakpoint 1, main () at test.c:4
4 int a = 10;
(gdb) break 5
Breakpoint 2 at 0x555555555155: file test.c, line 5.
(gdb) cond 2 a == 999
(gdb) cond 2 a == 10 if
Junk at end of expression
(gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y 0x0000555555555155 in main at test.c:5
stop only if a == 999
(gdb) c
Continuing.
Breakpoint 2, main () at test.c:5
5 a = a + 1; /* break-here */
(gdb)
We should not have hit the breakpoint because the condition would
evaluate to false.
Fix this problem by updating the condition expression of the breakpoint
after parsing the input successfully and checking that there is no
remaining junk.
gdb/ChangeLog:
2020-07-30 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* breakpoint.c (set_breakpoint_condition): Update the condition
expressions after checking that the input condition string parses
successfully and does not contain junk at the end.
gdb/testsuite/ChangeLog:
2020-07-30 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb.base/condbreak-bad.exp: Extend the test with scenarios
that attempt to overwrite an existing condition with a condition
that fails parsing and also with a condition that parses fine
but contains junk at the end.
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.