[cfe-dev] SIGBUS error from StringRef

[David Blaikie via cfe-dev]

Shooting from the hip, it sounds like your StringRef is dangling (pointing
to deallocated memory, etc). I'd suggest you try Valgrind to possibly get a
better sense of what's going on.

On Wed, May 4, 2016 at 6:18 AM, 詹石岩 via cfe-dev <cfe-dev at lists.llvm.org>
wrote:

> I wrote a clang tool based on libtooling.
> This tool will insert some code into the source file through Rewriter.
>
> I encounted SIGBUS when insert a sentence after a SourceLocation.
> I debugged using CLion and found this SIGBUS happend here:
>
> Rewriter.cpp, Line 257 @Rewriter::InsertText(SourceLocation Loc, String
> Ref Str, bool InsertAfter, bool IndentNewLine)
>
> the code writes:
> while(isWhitespaceExceptNL(MB[i]) //the* MB[i]* will cause SIGBUS
> sometimes.
>
> The MB is a instance of StringRef
>
> I encounted this problem only for the main.c and utils.c from
> graph500-2.1.4, in the mpi folder.
>
> when processing main.c, the problem happens when trying to insert a '\n'
> after the for statement in line 45:
> for(i=0;i<n;++i)  tmp+=x[i];
> -------------------^-----//try to insert here
>
> can anyone tells me how to check the problem?
>
> I used gcc4.8.4, Linux Mint 17.3, kernel version:3.13.0-24, core i7 4710M
>
> here is my code:
> (if I delete the code before
>
> if(!isa<CompoundStmt>(stmt))
>
> then the problem disappears)
>
> bool StmtHandler::InsertText(Stmt *stmt, string toInsert) {
>     //get rewriter from buffer
>     SourceLocation slc = stmt->getLocStart();
>     unsigned int fsl = TheContext.getFullLoc(slc).getSpellingColumnNumber();
>
>     string filename = TheContext.getSourceManager().getFilename(slc).str();
>     FileIdMap::iterator index = fileMap.find(filename);
>     FileID id = TheRewriter.getSourceMgr().getFileID(slc);
>     if(index == fileMap.end()){
>         fileMap[filename] = id;
>         //we need to judge whether the file was instrumented already
>         const RewriteBuffer &buffer = TheRewriter.getEditBuffer(id);
>         string content(buffer.begin(), buffer.end());
>         size_t pos = content.find('\n', 0);
>         string start = content.substr(0, pos + 1);
>         string comp = "//instrumented "+namespace_origin+"\n";
>         //if we can not write the file, we regard it as instrumented
>         std::error_code OutErrorInfo;
>         std::error_code ok;
>         llvm::raw_fd_ostream tmpFile(filename, OutErrorInfo, llvm::sys::fs::F_RW);
>         if(OutErrorInfo != ok){
>             fileInstrumented[id] = true;
>             return false;
>         }
>         //see if this file was ever instrumented
>         if(start != comp){
>             fileInstrumented[id] = false;
>             TheRewriter.InsertText(TheRewriter.getSourceMgr().getLocForStartOfFile(id), comp,false);
>         }else{
>             fileInstrumented[id] = true;
>             llvm::errs()<<"file "<<filename<<" was ignored.\n";
>             return false;
>         }
>
>     }else{
>         if(fileInstrumented[id])
>             return false;
>     }
>
>     if(!isa<CompoundStmt>(stmt)){
>         SourceLocation ST = stmt->getLocStart();
>
>         TheRewriter.InsertText(ST, "{\n", true, true);
>         TheRewriter.InsertText(ST, toInsert + "\n", true, true);
>         SourceLocation END = stmt->getLocEnd();
>        int offset = Lexer::MeasureTokenLength(END,
>                                                TheRewriter.getSourceMgr(),
>                                                TheRewriter.getLangOpts()) + 1;
>
>         SourceLocation END1 = END.getLocWithOffset(offset);
>         TheRewriter.InsertText(END1, "\n}", true, true);
>     }
>     else{
>         CompoundStmt *compstmt = cast<CompoundStmt>(stmt);
>         SourceLocation compLoc = compstmt->getLocStart();
>         TheRewriter.InsertText(compLoc.getLocWithOffset(1),"\n"+toInsert+"\n", true, true);
>     }
>     return true;
> }
>
>
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