-A mini-FAQ for valgrind, version 1.9.5
+A mini-FAQ for valgrind, version 1.9.6
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Last revised 22 Apr 2003
~~~~~~~~~~~~~~~~~~~~~~~~
+-----------------------------------------------------------------
+
Q1. Programs run OK on valgrind, but at exit produce a bunch
of errors a bit like this
Problem is that running __libc_freeres() in older glibc versions
causes this crash.
- WORKAROUND FOR 1.0.X versions of valgrind: The simple fix is to
- find in valgrind's sources, the one and only call to
- __libc_freeres() and comment it out, then rebuild the system. In
- the 1.0.3 version, this call is on line 584 of vg_clientfuncs.c.
- This may mean you get false reports of space leaks in glibc, but
- it at least avoids the crash.
-
WORKAROUND FOR 1.1.X and later versions of valgrind: use the
- --run-libc-freeres=no flag.
+ --run-libc-freeres=no flag. You may then get space leak
+ reports for glibc-allocations (please _don't_ report these
+ to the glibc people, since they are not real leaks), but at
+ least the program runs.
+-----------------------------------------------------------------
Q2. My program dies complaining that syscall 197 is unimplemented.
specific, glibc is asking your kernel to do a syscall which is
not listed in /usr/include/asm/unistd.h.
- The fix is simple. Somewhere near the top of vg_syscall_mem.c,
- add the following line:
+ The fix is simple. Somewhere near the top of
+ coregrind/vg_syscalls.c, add the following line:
#define __NR_fstat64 197
Rebuild and try again. The above line should appear before any
uses of the __NR_fstat64 symbol in that file. If you look at the
- place where __NR_fstat64 is used in vg_syscall_mem.c, it will be
- obvious why this fix works. NOTE for valgrind versions 1.1.0
- and later, the relevant file is actually coregrind/vg_syscalls.c.
+ place where __NR_fstat64 is used in vg_syscalls.c, it will be
+ obvious why this fix works.
+-----------------------------------------------------------------
Q3. My (buggy) program dies like this:
valgrind: vg_malloc2.c:442 (bszW_to_pszW):
is to fix your program so that it doesn't do any illegal memory
accesses. The above failure will hopefully go away after that.
+-----------------------------------------------------------------
Q4. I'm running Red Hat Advanced Server. Valgrind always segfaults at
startup.
-A4. Known issue with RHAS 2.1. The following kludge works, but
- is too gruesome to put in the sources permanently. Try it.
- Last verified as working on RHAS 2.1 at 20021008.
-
- Find the following comment in vg_main.c -- in 1.0.4 this is at
- line 636:
-
- /* we locate: NEW_AUX_ENT(1, AT_PAGESZ, ELF_EXEC_PAGESIZE) in
- the elf interpreter table */
-
- Immediately _before_ this comment add the following:
-
- /* HACK for R H Advanced server. Ignore all the above and
- start the search 18 pages below the "obvious" start point.
- God knows why. Seems like we can't go into the highest 18
- pages of the stack. This is not good! -- the 18 pages is
- determined just by looking for the highest proddable
- address. It would be nice to see some kernel or libc or
- something code to justify this. */
-
- /* 0xBFFEE000 is 0xC0000000 - 18 pages */
- sp = 0xBFFEE000;
-
- /* end of HACK for R H Advanced server. */
-
- Obviously the assignment to sp is the only important line.
+A4. Known issue with RHAS 2.1, due to funny stack permissions at
+ startup. However, valgrind-1.9.4 and later automatically handle
+ this correctly, and should not segfault.
+-----------------------------------------------------------------
Q5. I try running "valgrind my_program", but my_program runs normally,
and Valgrind doesn't emit any output at all.
it my_program is statically linked.
+-----------------------------------------------------------------
Q6. I try running "valgrind my_program" and get Valgrind's startup message,
but I don't get any errors and I know my program has errors.
To trace child processes, use the --trace-children=yes option.
+ If you are tracing large trees of processes, it can be less
+ disruptive to have the output sent over the network. Give
+ valgrind the flag --logsocket=127.0.0.1:12345 (if you want
+ logging output sent to port 12345 on localhost). You can
+ use the valgrind-listener program to listen on that port:
+ valgrind-listener 12345
+ Obviously you have to start the listener process first.
+ See the documentation for more details.
+
+-----------------------------------------------------------------
+
+Q7. My threaded server process runs unbelievably slowly on
+ valgrind. So slowly, in fact, that at first I thought it
+ had completely locked up.
+
+A7. We are not completely sure about this, but one possibility
+ is that laptops with power management fool valgrind's
+ timekeeping mechanism, which is (somewhat in error) based
+ on the x86 RDTSC instruction. A "fix" which is claimed to
+ work is to run some other cpu-intensive process at the same
+ time, so that the laptop's power-management clock-slowing
+ does not kick in. We would be interested in hearing more
+ feedback on this.
+
+-----------------------------------------------------------------
+
+Q8. My program dies (exactly) like this:
+
+ REPE then 0xF
+ valgrind: the `impossible' happened:
+ Unhandled REPE case
+
+A8. Yeah ... that I believe is a P4 specific instruction. Are you
+ building your app with -march=pentium4 or something like that?
+ Others have reported that removing the flag works around this.
+ In fact this is pretty easy to fix and I do have it on my
+ to-do-for-1.9.6 list.
+
+ I'd be interested to hear if you can get rid of it by changing
+ your application build flags.
+
+-----------------------------------------------------------------
+
+Q9. My program dies complaining that __libc_current_sigrtmin
+ is unimplemented.
+
+A9. Try the following. It is an experiment, but it might work.
+ We would very much appreciate you telling us if it does/
+ does not work for you.
+
+ In vg_libpthread.c, add the 3 functions below.
+
+ In vg_libpthread_unimp.c, remove the stubs for the same 3
+ functions.
+
+ Let me know if it helps. Quite a lot of other valgrind users
+ complain about this, but I have never been able to reproduce it,
+ so fixing it isn't easy. So it's useful if you can try.
+
+ int __libc_current_sigrtmin (void)
+ {
+ return -1;
+ }
+
+ int __libc_current_sigrtmax (void)
+ {
+ return -1;
+ }
+
+ int __libc_allocate_rtsig (int high)
+ {
+ return -1;
+ }
+
+-----------------------------------------------------------------
+
+Q10. I upgraded to Red Hat 9 and threaded programs now act
+ strange / deadlock when they didn't before.
+
+A10. Thread support on glibc 2.3.2+ with NPTL is not as
+ good as on older LinuxThreads-based systems. We have
+ this under consideration. Avoid Red Hat >= 8.1 for
+ the time being, if you can.
+
+-----------------------------------------------------------------
+
+Q11. I really need to use the NVidia libGL.so in my app.
+ Help!
+
+A11. NVidia also noticed this it seems, and the "latest" drivers
+ (version 4349, apparently) come with this text
+
+ DISABLING CPU SPECIFIC FEATURES
+
+ Setting the environment variable __GL_FORCE_GENERIC_CPU to a
+ non-zero value will inhibit the use of CPU specific features
+ such as MMX, SSE, or 3DNOW!. Use of this option may result in
+ performance loss. This option may be useful in conjunction with
+ software such as the Valgrind memory debugger.
+
+ Set __GL_FORCE_GENERIC_CPU=1 and Valgrind should work. This has
+ been confirmed by various people. Thanks NVidia!
+
+-----------------------------------------------------------------
+
+Q12. My program dies like this (often at exit):
+
+ VG_(mash_LD_PRELOAD_and_LD_LIBRARY_PATH): internal error:
+ (loads of text)
+
+A12. We're not entirely sure about this, and would appreciate
+ someone sending a simple test case for us to look at.
+ One possible cause is that your program modifies its
+ environment variables, possibly including zeroing them
+ all. Avoid this if you can.
+
+ In any case, you may be able to work around it like this:
+ Comment out the
+ call to VG_(core_panic) at coregrind/vg_main.c:1647 and see
+ if that helps. The text of coregrind/vg_main.c:1647 is as follows:
+
+ VG_(core_panic)("VG_(mash_LD_PRELOAD_and_LD_LIBRARY_PATH) failed\n");
+
+ and so it's this call you want to comment out.
+
+-----------------------------------------------------------------
+
+Q13. My program dies like this:
+
+ error: /lib/librt.so.1: symbol __pthread_clock_settime, version
+ GLIBC_PRIVATE not defined in file libpthread.so.0 with link time
+ reference
+
+A13. This is a total swamp. Nevertheless there is a way out.
+ It's a problem which is not easy to fix. Really the problem is
+ that /lib/librt.so.1 refers to some symbols
+ __pthread_clock_settime and __pthread_clock_gettime in
+ /lib/libpthread.so which are not intended to be exported, ie
+ they are private.
+
+ Best solution is to ensure your program does not use
+ /lib/librt.so.1.
+
+ However .. since you're probably not using it directly, or even
+ knowingly, that's hard to do. You might instead be able to fix
+ it by playing around with coregrind/vg_libpthread.vs. Things to
+ try:
+
+ Remove this
+
+ GLIBC_PRIVATE {
+ __pthread_clock_gettime;
+ __pthread_clock_settime;
+ };
+
+ or maybe remove this
+
+ GLIBC_2.2.3 {
+ __pthread_clock_gettime;
+ __pthread_clock_settime;
+ } GLIBC_2.2;
+
+ or maybe add this
+
+ GLIBC_2.2.4 {
+ __pthread_clock_gettime;
+ __pthread_clock_settime;
+ } GLIBC_2.2;
+
+ GLIBC_2.2.5 {
+ __pthread_clock_gettime;
+ __pthread_clock_settime;
+ } GLIBC_2.2;
+
+ or some combination of the above. After each change you need to
+ delete coregrind/libpthread.so and do make && make install.
+
+ I just don't know if any of the above will work. If you can
+ find a solution which works, I would be interested to hear it.
+
+ To which someone replied:
+
+ I deleted this:
+
+ GLIBC_2.2.3 {
+ __pthread_clock_gettime;
+ __pthread_clock_settime;
+ } GLIBC_2.2;
+
+ and it worked.
+
+-----------------------------------------------------------------
(this is the end of the FAQ.)
projects / thirdparty / valgrind.git / commitdiff
