Patch to mangle __uuidof expressions under -fms-extensions

[jahanian]

On Sep 22, 2014, at 5:15 PM, John McCall <rjmccall at apple.com> wrote:

> On Sep 22, 2014, at 4:20 PM, jahanian <fjahanian at apple.com> wrote:
>> This patch allows mangling of microsoft’s __uuidof expression for the Itanium ABI when under -fms-extensions
>> // rdar://17784718
> 
> +  case Expr::CXXUuidofExprClass: {
> +    if (!getASTContext().getLangOpts().MicrosoftExt) {
> +      DiagnosticsEngine &Diags = Context.getDiags();
> +        unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
> +                                    "cannot yet mangle __uuidof expression");
> +        Diags.Report(E->getExprLoc(), DiagID)
> +        << E->getStmtClassName() << E->getSourceRange();
> 
> You don’t need this.  We should never see these expressions except that
> language flag is set, and even if we do, it’s okay to mangle them this way.
> 
> +    } else {
> +        const CXXUuidofExpr *UE = cast<CXXUuidofExpr>(E);
> +        // This CXXUuidofExpr is mangled as-if it were actually a VarDecl from
> +        // const __s_GUID _GUID_{lower case UUID with underscores}
> +        StringRef Uuid = UE->getUuidAsStringRef(Context.getASTContext());
> +        std::string Name = "_GUID_" + Uuid.lower();
> +        std::replace(Name.begin(), Name.end(), '-', '_');
> +        Out << "$E?";
> +        Out << Name << "@@3U__s_GUID@@B";
> +    }
> 
> You need to use an Itanium-style mangling here, not a Microsoft-style one.
> That specifically means only using alphanumeric characters.
> 
> Also, since we’re using a different mangling, we should also properly
> handle dependent operands instead of assuming that the operand can
> always be fully resolved.
> 
> In the Itanium scheme, this falls into the general category of a
> vendor-extended operator, which is mangled as
>   u <name-of-operator> <operands...>
> As far as I can tell, it’s impossible to demangle these without knowledge of
> the specific vendor extension, because nothing in the mangling actually
> indicates how many operands follow.  So I don’t see any reason to actually
> insist that the operand actually be an expression, which is good, because
> __uuidof is like sizeof in that its operand can be either a type or an expression.
> 
> For sizeof, the mangling prefix is either “st” or “sz”, respectively.
> So let’s use these manglings:
> 
>   u8__uuidoft <type>          # __uuidof (a type)
>   u8__uuidofz <expression>    # __uuidof (an expression)

Hi John,
Please review the new patch.
- Thanks, Fariborz


> 
> John.

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