KDevelop apparently crashes due to a file that contains "#pragma clang __debug crash"

[Kevin Funk]

On Tuesday, 25 October 2016 10:43:29 CEST Kevin Funk wrote:
> On Tuesday, 25 October 2016 00:14:32 CEST Johannes Schaub wrote:
> > I wanted to browse the LLVM/Clang GIT checkout, but indexing the
> > project directory was very slow and sometimes it crashed (SIGILL and
> > SIGSEGV).
> > 
> > When people in #kdevelop told me to enable logging using
> > QT_LOGGING_RULES="kdev-clang=true", it turned out that clang kept
> > crashing on files in clang's testsuites. Digging into one of the
> > files, it contains
> > 
> >    #pragma clang __debug crash
> > 
> > This probably causes kdevelop to crash. In most cases (unfortunately)
> > this appears to be catched by llvm's crash handler and transformed to
> > a "return false".
> 
> Correct, usually libclang/LLVM handles these kind of crashes in its 'crash
> recovery context' and recovers, as you can see here:
> 
> During parsing of llvm.git:
> 
> libclang: crash detected during parsing: {
>   'source_filename' : '/home/kfunk/devel/src/llvm/tools/clang/test/Index/
> crash-recovery.c'
>   'command_line_args' : ['clang', '-ferror-limit=100', '-fspell-checking',
> '- Wdocumentation', '-Wunused-parameter', '-Wunreachable-code', '-Wall', '-
> std=c99', '-nostdinc', '-xc', '-isystem/usr/local/include',
> '-isystem/usr/lib/ llvm-3.8/lib/clang/3.8.1/include',
> '-isystem/usr/include/x86_64-linux-gnu', '- isystem/usr/include',
> '-I/home/kfunk/devel/src/llvm/include', '-I/home/kfunk/
> devel/src/llvm/tools/clang/include', '-imacros', '/tmp/kdevelop.Vd3748'],
> 'unsaved_files' : [...],
>   'options' : 45,
> }
> [kdevelop(3748)/(default) unknown(0): clang_parseTranslationUnit2 return
> with error code 2
> [kdevelop(3748)/(default) unknown(0):   (start KDevelop with
> `KDEV_CLANG_DISPLAY_DIAGS=1 kdevelop` to see more diagnostics)
> [kdevelop(3748)/(default) unknown(0): Failed to parse translation unit: "/
> home/kfunk/devel/src/llvm/tools/clang/test/Index/crash-recovery.c"
> 
> => No crash.
> 
> > My suspicion is that the SIGILL and SIGSEGV I
> > noticed are due to this pragma and the inability to catch the crash in
> > rare cases (the crash handler is best-effort).
> 
> Correct as well, it cannot possibly handle all cases. I just ran KDevelop on
> llvm.git once more and it indeed crashes on the following file for me --
> investigating this now:
> 
> [kdevelop(5363)/(kdevplatform.language) unknown(0): creating parse-job
> "/home/ kfunk/devel/src/llvm/tools/clang/test/SemaCXX/attr-gnu.cpp" new
> count of active parse-jobs: 2
> zsh: segmentation fault  KDEV_BACKGROUNDPARSER_MAXTHREADS=1 kdevelop -s llvm

Okay, that's fixed by:
  https://reviews.llvm.org/D25308

That file even makes Clang (tested 3.8 & 3.9) itself unhappy:

$ clang++-3.9 -std=gnu++11 test/SemaCXX/attr-gnu.cpp
(...)
1.      test/SemaCXX/attr-gnu.cpp:32:53: current parser token ';'
2.      test/SemaCXX/attr-gnu.cpp:32:1: parsing struct/union/class body 'Tu'
clang: error: unable to execute command: Segmentation fault
clang: error: clang frontend command failed due to signal (use -v to see 
invocation)

Anyhow, I can see only these two solutions to avoid running into problems like 
this:

- Use the latest libclang in KDevelop 
  (IOW the one compiled from llvm.git/clang.git)
- Ignore directories containing regression tests / crash tests

Hope that helps,
Kevin

> > KDevelop should disable handling of this and similar pragmas in clang,
> > if possible.
> 
> Problem with parsing the LLVM/Clang code of course: *If* there's a crash in
> libclang, and the crash is fixed in their trunk version, then usually a
> regression test will be added as well. KDevelop, likely using an *older*
> version of LLVM/Clang will try to parse the regression test... and crash.
> 
> I don't see how we could ever avoid this scenario. Of course there's the
> possibility to make KDevelop ignore certain directories in the LLVM/Clang
> tree [1] (e.g. the regression test suite).
> 
> Will investigate the crash now. For the time being, you could ignore the
> directories containing 'dangerous' files: [1].
> 
> Regards,
> Kevin
> 
> [1]
> http://askubuntu.com/questions/136529/how-to-exclude-a-folder-from-a-kdevel
> op-project


-- 
Kevin Funk | kfunk at kde.org | http://kfunk.org
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