Assertion failure when mangling complex decltype

Clang Frontend
#1

Hi all,

On release_70, for the example code:

#include <type_traits>
class Node {};
template
void buildGenericSCCs(GetBeginT &&GetBegin) {
decltype(GetBegin(std::declval<Node &>())) DFSStack;
}

In Mangle.h when calling mangleCXXName() on VarDecl of DFSStack, assertion triggered:

tools/clang/lib/AST/ItaniumMangle.cpp:4317: void (anonymous namespace)::CXXNameMangler::mangleFunctionParam(const clang::ParmVarDecl *): Assertion `parmDepth < FunctionTypeDepth.getDepth()’ failed.

Do anyone have any ideas on the cause of it? Thanks

#2

Wait, why are we trying to mangle the local var decl here? Doesn’t seem to repro on TOT for me, can you provide a backtrace/preprocessed source/a clang invocation for this?

Erik

#3

Reproducible on TOT. Confirmed!

Thanks!

#4

The mangler is only designed to produce mangled names for declarations that have symbols. You cannot expect to be able to pass other declarations to it and get a meaningful result back (or even for it to not crash).

If you want a unique identifier for an arbitrary declaration for some reason, USRs may be a better fit.