sammccall added inline comments.
================ Comment at: clang/test/CodeGenCXX/mangle.cpp:805 - // CHECK-LABEL: define weak_odr void @_ZN6test341fIiEEvDTstDTplcvT__EcvS1__EEE + // CHECK-LABEL: define weak_odr void @_ZN6test341fIiEEvm template void f<int>(decltype(sizeof(1))); ---------------- sammccall wrote: > GCC mangles this as `_ZN6test341fIiEEvDTstDTplcvT__EcvS1__EEE`, so we're > breaking compat here :-\ > > And in fact we're just incorrect. > https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling: > > > If the operand expression of decltype is not instantiation-dependent then > > the resulting type is encoded directly. > > Here, instantiation-dependent *is* explicitly defined as "type-dependent or > value-dependent or ...". And therefore these cases must not be "encoded > directly", including the motivating case (decltype(N) where N is a typed > constant whose initializer is value-dependent). > > We could consider not two but *three* types of decltypetypes: > - decltype(type-dependent), which is sugar for a canonical > DependentDeclTypeType > - decltype(instantiation-but-not-type-dependent), which is still sugar for a > concrete canonical type (per C++17) but mangles using the expr (per cxxabi) > - decltype(non-dependent), which is sugar for a concrete canonical type and > mangles directly > > This only works if it's OK for mangling to depend on non-canonical type > details - I don't know whether this is the case. @rsmith - any hints here? Hmm, my naive reading of the mangle code matches what I described. The big comment in ItaniumMangle talks about related issues: https://github.com/llvm/llvm-project/blob/24238f09edb98b0f460aa41139874ae5d4e5cd8d/clang/lib/AST/ItaniumMangle.cpp#L2541-L2572 I don't really understand what's going on here, sorry. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D87349/new/ https://reviews.llvm.org/D87349 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
