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From: "thiago at kde dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/69549] Named Address Spaces does not compile in C++
Date: Tue, 23 Mar 2021 01:36:18 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D69549

--- Comment #7 from Thiago Macieira <thiago at kde dot org> ---
(In reply to Andrew Pinski from comment #6)
> The above is not the reason why namespaces are not handled in GCC's C++
> front-end.  The reason why they are not handled in C++ is because you need
> to handle them in overloads and templates correctly.  Does clang handle
> those correctly or does it ignore that issue?

It handles them:

$ clang -O2 -S -o - -include stdint.h -xc++ - <<<'template  <typename T> vo=
id
f(T); void f() { auto tib =3D (void * __seg_fs*)(0); f(tib); }' | c++filt=20
        .text
        .file   "-"
        .globl  f()                   # -- Begin function f()
        .p2align        4, 0x90
        .type   f(),@function
f():                                  # @f()
        .cfi_startproc
# %bb.0:
        xorl    %edi, %edi
        jmp     void f<void* AS257*>(void* AS257*)     # TAILCALL

The mangled symbol was _Z1fIPU5AS257PvEvT_. That "AS257" is encoded as U5AS=
257,
which is an extended qualifier.

<https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangle.qualified-type>:
5.1.5.1 Qualified types


  <qualified-type>     ::=3D <qualifiers> <type>

  <qualifiers>         ::=3D <extended-qualifier>* <CV-qualifiers>
  <extended-qualifier> ::=3D U <source-name> [<template-args>] # vendor ext=
ended
type qualifier
  <CV-qualifiers>      ::=3D [r] [V] [K]    # restrict (C99), volatile, con=
st

  <ref-qualifier>      ::=3D R              # & ref-qualifier
  <ref-qualifier>      ::=3D O              # && ref-qualifier=