[cfe-dev] libclang unexpected diagnostic

[Ted Kremenek]

On Dec 18, 2010, at 2:03 AM, jiyang zhao wrote:

> hi guys, i write a programme using libclang , as follows
> 
> //clang_test.cpp
> int main( int argc, char** argv )
> {
>     CXIndex Index = clang_createIndex( 0, 0 );
>     CXTranslationUnit TU = clang_parseTranslationUnit( Index, 0, argv, argc, 0, 0, CXTranslationUnit_None );
> 
>     if(TU == NULL)
>         return -1;
> 
>     for( unsigned I=0, N=clang_getNumDiagnostics( TU ); I<N; ++I )
>     {
>         CXDiagnostic Diag = clang_getDiagnostic( TU, I );
>         /*
>          */
>         CXString String = clang_formatDiagnostic( Diag, clang_defaultDiagnosticDisplayOptions() );
>         fprintf( stderr, "Diag: %s\n", clang_getCString( String ) );
>         clang_disposeString( String );
> 
>         /*
>          */
>         for( unsigned J=0, M=clang_getDiagnosticNumFixIts( Diag ); J!=M; ++J )
>         {
>             CXSourceRange Range;
>             CXString Str2 = clang_getDiagnosticFixIt( Diag, J, &Range );
>             const char* str = clang_getCString( Str2 );
>             if( str!= 0 )
>             {
>                 fprintf( stderr, "FixIt: %s\n", str );
>                 CXSourceLocation Start = clang_getRangeStart( Range );
>                 CXSourceLocation End = clang_getRangeEnd( Range );
>                 unsigned line = 0;
>                 unsigned column = 0;
>                 clang_getSpellingLocation( Start, 0, &line, &column, 0 );
>                 fprintf( stderr, "Range start: line [%d], column [%d]\n", line, column );
>                 clang_getSpellingLocation( End, 0, &line, &column, 0 );
>                 fprintf( stderr, "Range end: line [%d], column [%d]\n", line, column );
>             }
> 
>             clang_disposeString( Str2 );
>         }
>         clang_disposeDiagnostic(Diag);
>     }
> 
>     clang_disposeTranslationUnit( TU );
>     clang_disposeIndex( Index );
>     return 0;
> }
> //test.cpp
> #include <stdio.h>
> 
> int PrintExtent(  )
> {
> }
> 
> when run ./clang_test test.cpp, it prints 
> Diag: warning: ./clang_test: 'linker' input unused when '-fsyntax-only' is present
> Diag: test.cpp:5:1: warning: control reaches end of non-void function [-Wreturn-type]
> 
> My question is why does it print the first message, and how can i forbid it to print this message.
> 
> Thanks.

The first warning comes from the driver when processing the command line arguments.  You are essentially passing a flag to the compiler that would only be used when doing a link, but you are doing -fsyntax-only.

Internally you can suppress the warning by remapping the diagnostic to "ignore", but there is no API for that in the high-level libclang API (unless the warning has a matching -WFOO command line flag, which allows you to pass -Wno-FOO to suppress the warning).
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