[LLVMbugs] [Bug 11738] New: clang segfaults when file changes

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11738

             Bug #: 11738
           Summary: clang segfaults when file changes
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: chris at bubblescope.net
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


The following bug is probably very stupid, and I don't mind if it gets closed,
but I thought I would report it anyway.

Take any reasonable sized C++ file, call it X.cc (I preprocessed a boost file
to get a ~2M file)

Execute the following command:

for i in `seq 10000`; do cat X.cc > t.cc; done &

While that is spinning in the background, type:

clang++ t.cc -c

A few times, and you are likely to see a crash like the one before. I am fairly
sure this is not from clang++ just seeing a truncated file, as I have tried to
truncate the file I was using in many places, and have not seen clang crash (I
actually found this bug when my fuzzer started misbehaving and changing the
file while clang was compiling. I get a segfault like the one below.

Note the files mentioned at the bottom, writen to /tmp, compile fine (well,
often with errors, but no segfaults).

0  clang           0x0000000001b5f98f
1  clang           0x0000000001b5fe19
2  libpthread.so.0 0x00007f93be567060
3  clang           0x0000000000fbd1ac
4  clang           0x0000000000fc1af2
clang::SourceManager::getLineNumber(clang::FileID, unsigned int, bool*) const +
482
5  clang           0x0000000000fc2862
clang::SourceManager::getPresumedLoc(clang::SourceLocation) const + 450
6  clang           0x0000000000f78283
clang::Preprocessor::HandleDigitDirective(clang::Token&) + 2739
7  clang           0x0000000000f7dd33
clang::Preprocessor::HandleDirective(clang::Token&) + 1411
8  clang           0x0000000000f60128
clang::Lexer::LexTokenInternal(clang::Token&) + 2104
9  clang           0x0000000000f6181f
clang::Lexer::LexTokenInternal(clang::Token&) + 7983
10 clang           0x0000000000882a38
11 clang           0x000000000087c73a
clang::Parser::ExpectAndConsume(clang::tok::TokenKind, unsigned int, char
const*, clang::tok::TokenKind) + 762
12 clang           0x00000000008905ee
clang::Parser::ParseDeclGroup(clang::Parser::ParsingDeclSpec&, unsigned int,
bool, clang::SourceLocation*, clang::Parser::ForRangeInit*) + 1886
13 clang           0x000000000089695c
clang::Parser::ParseSimpleDeclaration(clang::ASTOwningVector<clang::Stmt*,
32u>&, unsigned int, clang::SourceLocation&, clang::ParsedAttributes&, bool,
clang::Parser::ForRangeInit*) + 652
14 clang           0x0000000000896b02
clang::Parser::ParseDeclaration(clang::ASTOwningVector<clang::Stmt*, 32u>&,
unsigned int, clang::SourceLocation&,
clang::Parser::ParsedAttributesWithRange&) + 178
15 clang           0x000000000087eb4d
clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&,
clang::Parser::ParsingDeclSpec*) + 893
16 clang           0x000000000087f628
clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&) + 168
17 clang           0x00000000008543cd clang::ParseAST(clang::Sema&, bool) + 269
18 clang           0x000000000060101d
clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 317
19 clang           0x00000000005e7a1a
clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 1114
20 clang           0x00000000005dc4b2 cc1_main(char const**, char const**, char
const*, void*) + 866
21 clang           0x00000000005e62be main + 702
22 libc.so.6       0x00007f93bd83430d __libc_start_main + 237
23 clang           0x00000000005dbff9
Stack dump:
0.    Program arguments: /scratch/dist/clang/bin/clang -cc1 -triple
x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free
-disable-llvm-verifier -main-file-name t.cc -mrelocation-model static
-mdisable-fp-elim -masm-verbose -mconstructor-aliases -munwind-tables
-target-cpu x86-64 -target-linker-version 2.21.53.20110810
-momit-leaf-frame-pointer -coverage-file t.o -resource-dir
/scratch/dist/clang/bin/../lib/clang/3.1 -fmodule-cache-path
/var/tmp/clang-module-cache -internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../include/c++/4.6 -internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../include/c++/4.6/x86_64-linux-gnu
-internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../include/c++/4.6/backward
-internal-isystem /usr/local/include -internal-isystem
/scratch/dist/clang/bin/../lib/clang/3.1/include -internal-externc-isystem
/usr/include/x86_64-linux-gnu -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdeprecated-macro
-fdebug-compilation-dir /home/caj/temp -ferror-limit 19 -fmessage-length 136
-mstackrealign -fgnu-runtime -fobjc-runtime-has-arc -fobjc-runtime-has-weak
-fobjc-fragile-abi -fcxx-exceptions -fexceptions -fdiagnostics-show-option
-fcolor-diagnostics -o t.o -x c++ t.cc 
1.    clang: error: unable to execute command: Bus error
clang: error: clang frontend command failed due to signal (use -v to see
invocation)
clang: note: diagnostic msg: Please submit a bug report to
http://llvm.org/bugs/ and include command line arguments and all diagnostic
information.
clang: note: diagnostic msg: Preprocessed source(s) and associated run
script(s) are located at:
clang: note: diagnostic msg: /tmp/t-VkNgCT.ii
clang: note: diagnostic msg: /tmp/t-VkNgCT.sh

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