f7088df3b1
Joel contacted me offlist with a question about a warning that one of his customers was seeing. The message came from the new linker-debugger interface, which uses SDT probes internally. The warning said: (gdb) run [...] warning: Probes-based dynamic linker interface failed. Reverting to original interface. Argument to arithmetic operation not a number or boolean. This should not have happened in the environment the customer was using (RHEL-6.x), so I found it strange. Another thing caught my attention: the last message, saying "Argument to arithmetic operation not a number or boolean.". Joel kindly investigated the issue further, and found the answer for this. To quote him: (gdb) set lang c (gdb) p 48+$ebp $4 = (void *) 0xffffd0f8 So far so good. But... (gdb) set lang ada (gdb) p 48+$ebp Argument to arithmetic operation not a number or boolean. Ooops! Interestingly, if you revert the order of the operands... (gdb) p $ebp+48 $5 = (access void) 0xffffd0f8 So the problem is doing pointer arithmetics when the language is set to Ada. I remembered that, during the parsing and the evaluation of SDT probe arguments, the code sets the language as current_language, because, at that time, I thought it was not necessary to worry about the language given that the code implements its own parser. I was wrong. So here is a patch to fix that, by setting the language as C, which should guarantee that the maths are done in the right way (TM). It was somewhat hard to find a reproducer for this issue. In the end, what I had to do was to create a testcase that used the %ebp register on some displacement (e.g., "-4(%ebp)"), which finally triggered the bug. I am not sure why I could not trigger it when using other registers, but I did not want to spend too much time investigating this issue, which seemed like an Ada issue. Also, because of this peculiar way to trigger the problem, the testcase only covers x86-like targets (i.e., i*86 and x86_64 with -m32). Joel kindly tested this for me, and it worked. I also ran a full regression test here on my Fedora 20 x86_64, and everything is fine. I will push this patch in a few days if there are no comments. gdb/ChangeLog: 2014-10-14 Sergio Durigan Junior <sergiodj@redhat.com> * stap-probe.c (stap_parse_argument): Initialize expout explicitly using language_c, instead of current_language. gdb/testsuite/ChangeLog: 2014-10-14 Sergio Durigan Junior <sergiodj@redhat.com> * gdb.arch/stap-eval-lang-ada.S: Likewise. * gdb.arch/stap-eval-lang-ada.c: Likewise. * gdb.arch/stap-eval-lang-ada.exp: New file. |
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README
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.