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

[Kevin Funk]

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
 
> 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-kdevelop-project


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