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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109887] Different mangled name for template specialization
 for clang and gcc
Date: Wed, 17 May 2023 10:19:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109887

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
So, simpler testcase would be
#include <type_traits>

template <class T>
std::enable_if_t <std::is_integral <T>::value, int>
foo() { return 0; }

int a =3D foo<int> ();

GCC mangles this as
_Z3fooIiENSt9enable_ifIXsrSt11is_integralIT_E5valueEiE4typeEv
while clang as
_Z3fooIiENSt9enable_ifIXsr3std11is_integralIT_EE5valueEiE4typeEv
but c++filt is able to demangle both as
std::enable_if<std::is_integral<int>::value, int>::type foo<int>()
So, the difference between the two is that gcc uses substitution St for std=
::
while clang doesn't.
In https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling sr is
<unresolved-name> ::=3D [gs] <base-unresolved-name>                     # x=
 or
(with "gs") ::x
                    ::=3D sr <unresolved-type> <base-unresolved-name>     #=
 T::x
/ decltype(p)::x
...
and
<unresolved-type> ::=3D <template-param> [ <template-args> ]            # T=
:: or
T<X,Y>::
                    ::=3D <decltype>                                      #
decltype(p)::
                    ::=3D <substitution>
and
<substitution> ::=3D St # ::std::
among other things, so I think st is what should be used instead of 3std.=