[cfe-dev] [llvm-dev] Detecting invalid functions of template specialisations

陳韋任 via cfe-dev cfe-dev at lists.llvm.org
Fri Nov 24 17:54:48 PST 2017

fwd to cfe-dev list.

2017-11-24 19:34 GMT+08:00 Dimitar Dobrev via llvm-dev <
llvm-dev at lists.llvm.org>:

> Hello all.
> I need your advice about a fix I am thinking about. See this code:
> https://clang.llvm.org/doxygen/SemaOverload_8cpp_source.html#l12230
> I think that if the found function is invalid
> (clang::Decl::isInvalidDecl()) this case should fall through to
> https://clang.llvm.org/doxygen/SemaOverload_8cpp_source.html#l12338 .
> I am afraid I don’t know enough about the code of Clang and about
> compilers in general in order to think of a test myself. Instead, I
> could explain the problem I have and why I think something like this
> would help.
> So, I work on https://github.com/mono/CppSharp , it’s a generator for
> language bindings to C++.
> I need to get symbols of template specialisations so that I can compile
> them and invoke them from the target language. So I parse the input
> headers and use the Clang API to instantiate each specialisation I need:
> Sema::InstantiateClassTemplateSpecialization
> However, in many cases functions of specialisations are invalid. For
> example, the body of the templated function uses == while the T type
> argument does not support this operator. In order to find such
> functions, I use a custom DiagnosticConsumer combined with
> Sema::InstantiateFunctionDefinition for each function.
> I am now going to explain the actual problem.
> Some of these functions are inlined and use each other. A typical
> example is != which uses == internally, as in != { return !==; }. Let’s
> say the == is invalid. InstantiateFunctionDefinition detects that but it
> adds the == as a valid overload anyway. So when the != is parsed, Clang
> says: I have found a valid overload for the == inside and I am returning
> it so there’s no error in this function.
> This problem also affects your stack traces because they show the CPP
> the == was originally requested from but do now show it for the !=.
> Please share your opinions about the fix I have suggested and about the
> problem in general.
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Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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