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__bases and __direct_bases intrinsics are not supported (N2965) #24289

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llvmbot opened this issue Jun 23, 2015 · 8 comments
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__bases and __direct_bases intrinsics are not supported (N2965) #24289

llvmbot opened this issue Jun 23, 2015 · 8 comments
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bugzilla Issues migrated from bugzilla c++ clang:frontend Language frontend issues, e.g. anything involving "Sema" extension:gnu wontfix Issue is real, but we can't or won't fix it. Not invalid

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@llvmbot
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llvmbot commented Jun 23, 2015 •
edited by Endilll

Bugzilla Link 23915
Version trunk
OS Linux
Reporter LLVM Bugzilla Contributor
CC @tstellar,@jwakely

Extended Description

Clang cannot compile GCC header tr2/type_traits (see below).
Type traits "bases" and "direct_bases" were proposed as N2965 for C++11 standard, but were not included.
The feature is well-documented (see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2965.html) and is supported by GCC.
There are some questions and requests regarding this feature on developer forums (for example, http://stackoverflow.com/questions/18435001/what-is-the-status-of-n2965-stdbases-and-stddirect-bases).

$ clang --version
clang version 3.7.0 (trunk)
Target: x86_64-unknown-linux-gnu
Thread model: posix

$ cat test.cpp
#include <tr2/type_traits>
$ clang -std=c++11 -c test.cpp
In file included from test.cpp:1:
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:90:45: error: '_Tp' does not refer to a value
      typedef __reflection_typelist<__bases(_Tp)...>            type;
                                            ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:87:21: note: declared here
  template<typename _Tp>
                    ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:97:52: error: '_Tp' does not refer to a value
      typedef __reflection_typelist<__direct_bases(_Tp)...>     type;
                                                   ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:94:21: note: declared here
  template<typename _Tp>
                    ^
2 errors generated.

As you can see, Clang does not support __bases and __direct_bases intrinsics.

Alexey Frolov

Software Engineer
Intel Compiler Team
Intel
@jwakely
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jwakely mannequin commented Jan 15, 2016 •
edited by Endilll

I'm considering using __direct_bases in libstdc++'s <random> so it would not only be used in an obscure, non-standard extension. Would implementing that intrinsic be a problem for Clang?

If necessary I could check __clang__ and use an inferior solution instead of __direct_bases, but I'd prefer not to do that extra work.

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 10, 2021
@jgehrcke
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jgehrcke commented Feb 8, 2024 •
edited

Is this really still a known problem with recent releases of llvm/clang?

@Endilll
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Endilll commented Feb 8, 2024

Well, we still don't support those intrinsics, as far as I can tell. I'm not sure something will change today if no action was taken back then.
@jwakely is __direct_bases still interesting to libstdc++?

@jwakely
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jwakely commented Feb 8, 2024

No. I don't even remember what I was thinking of using it for. It's just an obscure, unused extension in a non-standard header.

@jwakely
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jwakely commented Feb 8, 2024

I've just pushed this to fix the problem including that header with Clang:
https://gcc.gnu.org/r14-8888-g5fb204aaf34b68

hubot pushed a commit to gcc-mirror/gcc that referenced this issue Feb 8, 2024
@jwakely
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
5fb204a 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
wangliu-iscas pushed a commit to plctlab/patchwork-gcc that referenced this issue Feb 8, 2024
@jwakely @ouuleilei-bot
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
1fd2dad 
Tested x86_64-linux. Pusued to trunk. I'll backport it too.

-- >8 --

These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
@Endilll
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Endilll commented Feb 8, 2024

Thank you for the timely response!

@Endilll Endilll closed this as not planned Won't fix, can't repro, duplicate, stale Feb 8, 2024
@Endilll Endilll added wontfix Issue is real, but we can't or won't fix it. Not invalid c++ extension:gnu labels Feb 8, 2024
@llvmbot
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llvmbot commented Feb 8, 2024

@llvm/issue-subscribers-c-1

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [23915](https://llvm.org/bz23915) | | Version | trunk | | OS | Linux | | Reporter | LLVM Bugzilla Contributor | | CC | @tstellar,@jwakely |

Extended Description

Clang cannot compile GCC header tr2/type_traits (see below).
Type traits "bases" and "direct_bases" were proposed as N2965 for C++11 standard, but were not included.
The feature is well-documented (see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2965.html) and is supported by GCC.
There are some questions and requests regarding this feature on developer forums (for example, http://stackoverflow.com/questions/18435001/what-is-the-status-of-n2965-stdbases-and-stddirect-bases).

$ clang --version
clang version 3.7.0 (trunk)
Target: x86_64-unknown-linux-gnu
Thread model: posix

$ cat test.cpp
#include &lt;tr2/type_traits&gt;
$ clang -std=c++11 -c test.cpp
In file included from test.cpp:1:
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:90:45: error: '_Tp' does not refer to a value
      typedef __reflection_typelist&lt;__bases(_Tp)...&gt;            type;
                                            ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:87:21: note: declared here
  template&lt;typename _Tp&gt;
                    ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:97:52: error: '_Tp' does not refer to a value
      typedef __reflection_typelist&lt;__direct_bases(_Tp)...&gt;     type;
                                                   ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/tr2/type_traits:94:21: note: declared here
  template&lt;typename _Tp&gt;
                    ^
2 errors generated.

As you can see, Clang does not support __bases and __direct_bases intrinsics.

Alexey Frolov

Software Engineer
Intel Compiler Team
Intel

@jgehrcke
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jgehrcke commented Feb 9, 2024 •
edited

Funky! I didn't even really understand the problem and got curious because we were facing a related one. Thanks for all the lovely momentum in here, this is a great example for splendid open-source collaboration.

hubot pushed a commit to gcc-mirror/gcc that referenced this issue Feb 16, 2024
@jwakely
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
e1a1e81 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.

(cherry picked from commit 5fb204a)
eebssk1 pushed a commit to eebssk1/m_gcc that referenced this issue Feb 17, 2024
@jwakely @eebssk1
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
2c9155f 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.

(cherry picked from commit 5fb204aaf34b68c427f5b2bfb933fed72fe3eafb)
Liaoshihua pushed a commit to Liaoshihua/ruyi-gcc that referenced this issue Mar 11, 2024
@jwakely @Liaoshihua
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
5ced647 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
Liaoshihua pushed a commit to Liaoshihua/ruyi-gcc that referenced this issue Mar 11, 2024
@jwakely @Liaoshihua
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
2582770 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
Liaoshihua pushed a commit to Liaoshihua/ruyi-gcc that referenced this issue Mar 11, 2024
@jwakely @Liaoshihua
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
3130a46 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
Liaoshihua pushed a commit to Liaoshihua/ruyi-gcc that referenced this issue Mar 11, 2024
@jwakely @Liaoshihua
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
32ea8b5 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
Liaoshihua pushed a commit to Liaoshihua/ruyi-gcc that referenced this issue Mar 11, 2024
@jwakely @Liaoshihua
libstdc++: Guard tr2::bases and tr2::direct_bases with __has_builtin
da840cf 
These non-standard extensions use GCC-specific built-ins. Use
__has_builtin to avoid errors when Clang compiles this header.

See llvm/llvm-project#24289

libstdc++-v3/ChangeLog:

	* include/tr2/type_traits (bases, direct_bases): Use
	__has_builtin to check if required built-ins are supported.
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