[Buildroot] [Bug 7208] New: Glibc C++ aplications crash if they use exceptions.

[Buildroot] [Bug 7208] New: Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

           Summary: Glibc C++ aplications crash if they use exceptions.
           Product: buildroot
           Version: 2014.05
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: critical
          Priority: P5
         Component: Other
        AssignedTo: unassigned at buildroot.uclibc.org
        ReportedBy: kwrzalik at gmail.com
                CC: buildroot at uclibc.org
   Estimated Hours: 0.0


I'm using a toolchain with glibc and the following simple program crashes:

#include <cstdio>

int main() {
  try {
    throw 42;
  } catch (int x) {
    printf("catch %d\n", x);
  }
}

with the following backtrace:

#0  0xb7747a92 in ?? () from /lib/ld-linux.so.2
#1  0xb74ac6b8 in raise () from /lib/libc.so.6
#2  0xb74adbae in abort () from /lib/libc.so.6
#3  0xb763903a in ?? () from /lib/libgcc_s.so.1
#4  0xb763936b in _Unwind_RaiseException () from /lib/libgcc_s.so.1
#5  0xb76d0304 in __cxa_throw () from /usr/lib/libstdc++.so.6
#6  0x080486c1 in main ()

when run on the host with proper ld-linux.so and run paths the stack trace is
as follows:

#0  0xb7fdc424 in __kernel_vsyscall ()
#1  0xb7d4073f in raise () from
/opt/gnl/usr/i686-gnl-linux-gnu/sysroot/lib/libc.so.6
#2  0xb7d41c5e in abort () from
/opt/gnl/usr/i686-gnl-linux-gnu/sysroot/lib/libc.so.6
#3  0xb7ecf0d9 in uw_init_context_1 (context=context at entry=0xbfffe680,
outer_cfa=outer_cfa at entry=0xbfffe860, outer_ra=0xb7f66424
<__cxxabiv1::__cxa_throw(void*, std:
:type_info*, void (*)(void*))+97>) at ../../../libgcc/unwind-dw2.c:1567
#4  0xb7ecf40a in _Unwind_RaiseException (exc=0x804a048) at
../../../libgcc/unwind.inc:88
#5  0xb7f66424 in __cxxabiv1::__cxa_throw (obj=0x804a068, tinfo=0x8049e50
<_ZTIi@@CXXABI_1.3>, dest=0x0) at
../../../../libstdc++-v3/libsupc++/eh_throw.cc:82
#6  0x08048924 in main () at dupa.cpp:8


In the discussion with tom_kos and wbx on IRC we managed to pin the problem
libgcc_s.so. The problem only appears when linking with dynamic libgcc_s.so. If
the program is compiled with -static-libgcc it runs correctly.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #1 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 2014-06-15 10:39:13 UTC ---
Which gcc version was used for the test? It can be useful to be able to match
libgcc/unwind-dw2.c:1567 from the backtrace with the appropriate source code.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #2 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-15 10:43:08 UTC ---
It comes from 4.9.0.

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[Buildroot] [Bug 7208] New: Glibc C++ aplications crash if they use exceptions.

[Mike Zick]

On Sun, 15 Jun 2014 10:29:22 +0000 (UTC)
bugzilla at busybox.net wrote:

> In the discussion with tom_kos and wbx on IRC we managed to pin the
> problem libgcc_s.so. The problem only appears when linking with
> dynamic libgcc_s.so. If the program is compiled with -static-libgcc
> it runs correctly.
>

The file libgcc_s.so is an ascii text, linker script.
It should be patchable.

PS: It is being installed to the target -
My guess, it matches the pattern used to transfer libgcc_s.so.1
(which is a dynamic library binary).

Mike

[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #3 from Thomas De Schampheleire <patrickdepinguin@gmail.com> 2014-06-15 14:40:11 UTC ---
Please also provide your .config file so other people can try to look at the
problem.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #4 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-15 14:52:47 UTC ---
Created attachment 5456
  --> https://bugs.busybox.net/attachment.cgi?id=5456
Buildroot configuration

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #5 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-15 17:54:22 UTC ---
The difference between compiling with -static-libgcc seems to boil down to the
following function:

_Unwind_Find_FDE

When compiled with -statlic-libgcc the function invocation ends up in glibc.
When -static-libgcc is not given, then this function is located in libgcc.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #6 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-15 20:10:59 UTC ---
It turns out that 900-musl-support.patch breaks exceptions when using glibc:

The proper exception handling in libgcc seems to need USE_PT_GNU_EH_FRAME
definition in  libgcc's unwind-dw2-fde-dip.c. However; the patch changes this
file to:

+#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) &&
defined(TARGET_DL_ITERATE_PHDR)
 # define USE_PT_GNU_EH_FRAME

Configure in host-gcc-final seems to be unable to locate
TARGET_DL_ITERATE_PHDR:
checking dl_iterate_phdr in target C library... unknown

In such case unwind-dw2-fde-dip.c falls back to unwind-dw2-fde.c which does not
do the job of finding a FDE and hence the crash.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #7 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 2014-06-15 22:55:49 UTC ---
Thanks a lot for the debugging! I'll have a closer look and see what is the
appropriate solution to make sure that C++ exceptions work with glibc, and that
we can still enable musl.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #8 from mail at waldemar-brodkorb.de 2014-06-16 08:28:30 UTC ---
Hi,

there is a discussion about this problem on the musl mailing list.
Just if you are not subscribed.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #9 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-16 09:05:27 UTC ---
IMHO a good solution would be to make patches conditional in some cases, e.g.
only use 900-musl-support.patch if C library is selected to musl. I guess it
would require quite amount of work thought...

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #10 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 2014-06-16 09:42:21 UTC ---
(In reply to comment #8)

> there is a discussion about this problem on the musl mailing list.
> Just if you are not subscribed.

Right, but I don't see our specific problem being taken into account. Rich
Felker concluded the thread with:

"""
Please note that these changes are not mandatory; at present,
everything works, but crtbegin.o and crtend.o are unnecessarily
bloated and this affects static binary size.
"""

Maybe we should tell him that the changes are breaking C++ exception handling
for glibc, when the musl patches are applied to gcc?

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #11 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 2014-06-16 09:43:40 UTC ---
(In reply to comment #9)
> IMHO a good solution would be to make patches conditional in some cases, e.g.
> only use 900-musl-support.patch if C library is selected to musl. I guess it
> would require quite amount of work thought...

That's certainly a solution, but I wouldn't qualify it as a good solution. We
try really hard to avoid having conditional patches.

Though, as a temporary solution it would certainly be acceptable. This problem
is a major bug in Buildroot 2014.05, and we have to solve it somehow.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #12 from bugdal at aerifal.cx 2014-06-16 14:04:29 UTC ---
The relevant part of the musl patch is intended to remove the hard-coding of
USE_PT_GNU_EH_FRAME as glibc-specific and instead detect via configure that it
should be used. My guess is that something's broken in the configure script
whereby TARGET_DL_ITERATE_PHDR is not getting detected correctly; perhaps the
test is not cross-compiler-compatible.

Based on the thread on the musl mailing list
(http://www.openwall.com/lists/musl/2014/06/16/2), I think if this is the
problem it would go undetected by musl, since when targetting musl gcc is still
producing an "old-style" crtbegin/crtend that works without
USE_PT_GNU_EH_FRAME. With glibc that doesn't happen because the crtstuff
preprocessor conditionals are still hard-coded for glibc.

In my opinion the "right" fix is finding and fixing whatever's wrong in
configure, but as a short-term solution, the conditional could be fixed to
hard-code USE_PT_GNU_EH_FRAME for glibc while detecting it elsewhere, as in:

+#if (!defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) &&
defined(TARGET_DL_ITERATE_PHDR)) || defined(__gnu_linux__)
 # define USE_PT_GNU_EH_FRAME

or something closer to whatever the upstream logic is for glibc.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #13 from Krzysztof Wrzalik <kwrzalik@gmail.com> 2014-06-16 18:58:47 UTC ---
If I'm looking at the right place, TARGET_DL_ITERATE_PHDR is defined in
output/build/host-gcc-final-4.9.0/gcc/configure.ac at line 5079. It looks like
it only gets set on a variant of solaris2. So this variable looks like a quick
hack to me rather than something one can depend on.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #14 from Sven Neumann <s.neumann@raumfeld.com> 2014-06-23 09:32:06 UTC ---
We are seeing the same problem with gcc 4.8.2 on our i586 platform. Code that
uses C++ exceptions and which used to work fine with the buildroot 2014.02
release now aborts when an exception is thrown.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #15 from Sven Neumann <s.neumann@raumfeld.com> 2014-06-23 11:40:01 UTC ---
(In reply to comment #14)
> We are seeing the same problem with gcc 4.8.2 on our i586 platform. Code that
> uses C++ exceptions and which used to work fine with the buildroot 2014.02
> release now aborts when an exception is thrown.

I have now verified that the problem goes away if I revert the commit that
introduces musl support to gcc 4.8.2.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

Thomas De Schampheleire <patrickdepinguin@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2014.08

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #16 from David Bachelart <david.bachelart@bbright.com> 2014-07-24 15:01:19 UTC ---
Created attachment 5528
  --> https://bugs.busybox.net/attachment.cgi?id=5528
Buildroot configuration

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #17 from David Bachelart <david.bachelart@bbright.com> 2014-07-24 15:01:57 UTC ---
Created attachment 5534
  --> https://bugs.busybox.net/attachment.cgi?id=5534
C code using pthread_exit

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #18 from David Bachelart <david.bachelart@bbright.com> 2014-07-24 15:09:29 UTC ---
Hi,

The 900-musl-support.patch also breaks the pthread_exit() function in pure
C-code. I enclose two files :
- basic buildroot configuration, toolchain using gcc 4.8.1 / glibc 2.18 /
binutils 2.22
- basic C code creating a thread that kills itself using pthread_exit()

Using a toolchain built from master, the main process receives the SIGABRT
signal.

If I remove the 900-musl-support.patch and rebuild the whole buildroot, the
code exits normally.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

--- Comment #19 from Thomas De Schampheleire <patrickdepinguin@gmail.com> 2014-08-09 15:44:53 UTC ---
What to do with this bug? We need a proper solution for the upcoming release...

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

Thomas Petazzoni <thomas.petazzoni@free-electrons.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at buildroot.uclibc |thomas.petazzoni at free-elect
                   |.org                        |rons.com

--- Comment #20 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 2014-08-14 17:24:35 UTC ---
Re-assigning to me, I'm working on it now.

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[Buildroot] [Bug 7208] Glibc C++ aplications crash if they use exceptions.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=7208

Peter Korsgaard <jacmet@uclibc.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #21 from Peter Korsgaard <jacmet@uclibc.org> 2014-08-17 07:43:23 UTC ---
The patch series fixing this has now been applied:

http://git.buildroot.net/buildroot/commit/?id=fea35ce67317aa0eee678fb9440814d1346fb2fb

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