[cfe-commits] r59502 - in /cfe/trunk: Driver/ include/clang/Analysis/ include/clang/Analysis/PathSensitive/ include/clang/Basic/ include/clang/Driver/ lib/Analysis/ lib/Basic/ lib/CodeGen/ lib/Driver/ lib/Lex/ lib/Parse/ lib/Sema/

Chris Lattner sabre at nondot.org
Wed Nov 19 21:27:55 PST 2008

On Nov 18, 2008, at 8:13 AM, Douglas Gregor wrote:
>> +  DiagnosticInfo &operator<<(const SourceRange &R) {
>> +    assert((unsigned)DiagObj->NumDiagArgs <
>> +           sizeof(DiagObj->DiagRanges)/sizeof(DiagObj-
>>> DiagRanges[0]) &&
>> +           "Too many arguments to diagnostic!");
>> +    DiagObj->DiagRanges[DiagObj->NumDiagRanges++] = &R;
>> +    return *this;
>> +  }
>> +
>> };
> These operator<<'s should be free functions, because we will certainly
> have other operator<<'s for DiagnosticInfo elsewhere in the compiler
> that must be free functions, e.g.,
> 	DiagnosticInfo& operator<<(DiagnosticInfo& DI, QualType Ty); // in
> clang/AST/Type.h
> and we don't want non-member and member operator<<'s overloaded
> because the available conversions on the first argument differ, and
> that causes overloading weirdness.

Yes, I totally agree.  Okay, I'm to the point where I want to do  
this.  However, this is not my day.  Please take a look at this patch:

I just move the operators out of the class in a straightforward way.   
With this patch, I get build errors like these:

Lexer.cpp: In function ‘char DecodeTrigraphChar(const char*,  
Lexer.cpp:352: error: no match for ‘operator<<’ in  
‘clang::Lexer::Diag(const char*, unsigned int) const((CP - 2u), 9u) <<  
std::operator+(const std::basic_string<_CharT, _Traits, _Alloc>&,  
_CharT) [with _Char
T = char, _Traits = std::char_traits<char>, _Alloc =  
Diagnostic.h:366: note: candidates are: clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, const std::string&)
Diagnostic.h:371: note:                 clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, const char*)
Diagnostic.h:376: note:                 clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, int)
Diagnostic.h:381: note:                 clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, unsigned int)
Diagnostic.h:386: note:                 clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, const clang::IdentifierInfo*)
Diagnostic.h:392: note:                 clang::DiagnosticInfo&  
clang::operator<<(clang::DiagnosticInfo&, const clang::SourceRange&)

This is the source line:
Lexer *L; char Res;
   L->Diag(CP-2, diag::trigraph_converted) << std::string()+Res;

This is a good point where we can step back and look at the amazing  
awfulness of this diagnostic.  It's 'pretty' printing out the  
expression in question, in a horribly mangled form.  Then it dumps out  
a candidate list, but manages to not tell me the types that it  
actually *has* on the LHS/RHS of the <<.  In practice, I think the  
problem is that Diag is returning a temporary:

class Lexer {
   DiagnosticInfo Diag(const char *Loc, unsigned DiagID) const;

and this isn't matching as the non-constant reference form of <<.   
Imagine if it told me that it had near match! :)

All bitching about diagnostics aside, how should I go about fixing  
this?  Should have hack the overloads to use const references and cast  
away the const?  Do you have a better suggestion?


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