[cfe-dev] segfault in lexing

[Chris Lattner]

On Jul 4, 2011, at 8:34 AM, harsh gupta wrote:

> I am using the lexer to get a stream of tokens for a file. However if there is a nested block comment,
> 
>  for eg /* some comment /*This is a nested comment*/ some more comment */ 
> 
> Then the lexer gives a segmentation fault. Is there any way to avoid this segmentation fault?

It's hard to tell without more information, you probably don't have diagnostics set up right.  Note that this is *not* a nested block comment, C doesn't have any such thing.  If you run this through 'clang -E' you'll see this warning:

t.c:1:24: warning: '/*' within block comment [-Wcomment]

which is probably being mishandled.

-Chris

> 
> The code that i am using is:
>     clang::DiagnosticOptions diagnosticOptions;
>     clang::TextDiagnosticPrinter *pTextDiagnosticPrinter = new clang::TextDiagnosticPrinter( llvm::outs(), diagnosticOptions);
>     llvm::IntrusiveRefCntPtr<clang::DiagnosticIDs> pDiagIDs;
>     clang::Diagnostic diagnostic(pDiagIDs,pTextDiagnosticPrinter);
> 
>     clang::LangOptions languageOptions;
>     clang::FileSystemOptions fileSystemOptions;
>     clang::FileManager fileManager(fileSystemOptions);
> 
> 
>     clang::SourceManager sourceManager( diagnostic, fileManager);
>     clang::HeaderSearch headerSearch(fileManager);
> 
>     clang::TargetOptions targetOptions;
>     targetOptions.Triple = llvm::sys::getHostTriple();
> 
>     clang::TargetInfo *pTargetInfo = 
>     clang::TargetInfo::CreateTargetInfo( diagnostic, targetOptions);
> 
>     clang::Preprocessor preprocessor( diagnostic, languageOptions, *pTargetInfo, sourceManager, headerSearch);
> 
>     const clang::FileEntry *pFile = fileManager.getFile( _outFilename);
>     sourceManager.createMainFileID(pFile);
>     preprocessor.EnterMainSourceFile();
> 
>     std::vector<GeneralCommand> cmdvect;
>     GeneralCommand cmd;
>     clang::Token token;
>     do {
>             preprocessor.Lex(token);
>             if( diagnostic.hasErrorOccurred())
>             {
>                 break;
>             }
> 
>    } while(token.isNot(clang::tok::eof));
> 
> 
> 
> And the backtrace is:
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000004708fc in clang::LangOptions::LangOptions (this=0x7fffffffbc38) at /home/harsh/Desktop/llvm/tools/clang/lib/Sema/../../include/clang/Basic/LangOptions.h:24
> 24	class LangOptions {
> (gdb) bt
> #0  0x00000000004708fc in clang::LangOptions::LangOptions (this=0x7fffffffbc38) at /home/harsh/Desktop/llvm/tools/clang/lib/Sema/../../include/clang/Basic/LangOptions.h:24
> #1  0x00000000007502c2 in clang::Lexer::Lexer (this=0x7fffffffbbb0, fileloc=..., features=..., 
>     BufStart=0x12a32cc8 "\n//#include <sys/wait.h>\n\n\n//#include <stdio.h>\n//#include <stdlib.h>\n//#include <errno.h>\n//#include <string.h>\n//#include <fcntl.h>\n//#include <sys/types.h>\n//#include <sys/stat.h>\n//#include <unist"..., 
>     BufPtr=0x12a338c4 "/*printf(\"God mode wasted \\n\")*/;\n/*\n\tswitch (gbuf[0]) \n\t\t{\n\t\t\tcase('h') :\n\t\t\t\tread(0,gbuf,6);\n\t\t\t\twrite(harpipe[1],gbuf,6);\n\t\t\tcase('t') :\n\t\t\t\tread(0,gbuf,6);\n\t\t\t\twrite(turpipe[1],gbuf,6);\n\t\t\tdefault"..., BufEnd=0x12a3411a "") at Lexer.cpp:117
> #2  0x0000000000750ae8 in clang::Lexer::MeasureTokenLength (Loc=..., SM=..., LangOpts=...) at Lexer.cpp:349
> #3  0x0000000000744116 in clang::TextDiagnosticPrinter::EmitCaretDiagnostic (this=0x12a0ab30, Loc=..., Ranges=0x7fffffffc010, NumRanges=0, SM=..., Hints=0x0, NumHints=0, Columns=0, OnMacroInst=0, 
>     MacroSkipStart=0, MacroSkipEnd=0) at TextDiagnosticPrinter.cpp:382
> #4  0x0000000000746a4d in clang::TextDiagnosticPrinter::HandleDiagnostic (this=0x12a0ab30, Level=clang::Diagnostic::Warning, Info=...) at TextDiagnosticPrinter.cpp:1041
> #5  0x0000000000921c04 in clang::DiagnosticIDs::ProcessDiag (this=0x0, Diag=...) at DiagnosticIDs.cpp:582
> #6  0x000000000091cc03 in clang::Diagnostic::ProcessDiag (this=0x7fffffffd410) at /home/harsh/Desktop/llvm/tools/clang/lib/Basic/../../include/clang/Basic/Diagnostic.h:608
> #7  0x000000000091b4a2 in clang::DiagnosticBuilder::Emit (this=0x7fffffffc460) at Diagnostic.cpp:225
> #8  0x0000000000421ee2 in clang::DiagnosticBuilder::~DiagnosticBuilder (this=0x7fffffffc460, __in_chrg=<value optimized out>)
>     at /home/harsh/Desktop/llvm/tools/clang/lib/Sema/../../include/clang/Basic/Diagnostic.h:696
> #9  0x000000000075369d in clang::Lexer::SkipBlockComment (this=0x129db190, Result=..., 
>     CurPtr=0x12a338c5 "*printf(\"God mode wasted \\n\")*/;\n/*\n\tswitch (gbuf[0]) \n\t\t{\n\t\t\tcase('h') :\n\t\t\t\tread(0,gbuf,6);\n\t\t\t\twrite(harpipe[1],gbuf,6);\n\t\t\tcase('t') :\n\t\t\t\tread(0,gbuf,6);\n\t\t\t\twrite(turpipe[1],gbuf,6);\n\t\t\tdefault "...) at Lexer.cpp:1629
> #10 0x0000000000754fd8 in clang::Lexer::LexTokenInternal (this=0x129db190, Result=...) at Lexer.cpp:2248
> #11 0x00000000007101e8 in clang::Lexer::Lex (this=0x129db190, Result=...) at /home/harsh/Desktop/llvm/tools/clang/lib/Frontend/../../include/clang/Lex/Lexer.h:131
> #12 0x00000000007102d5 in clang::Preprocessor::Lex (this=0x7fffffffc650, Result=...) at /home/harsh/Desktop/llvm/tools/clang/lib/Frontend/../../include/clang/Lex/Preprocessor.h:507
> #13 0x00000000007c2c84 in MyRewriter::getLexerTokens (this=0x7fffffffd750) at MyRewriter.cpp:304
> #14 0x00000000007c2847 in MyRewriter::getParseTrees (this=0x7fffffffd750) at MyRewriter.cpp:263
> #15 0x00000000007bdf26 in GeneralCandidate::parse (this=0xff09160) at GeneralCandidate.cpp:15
> #16 0x00000000007e3a10 in main () at CPPMain.cpp:1111
> 
> Harsh Gupta
> 
> 
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