[llvm-bugs] [Bug 51254] New: can't include cxxabi.h using libstdc++ ABI with libc++

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=51254

            Bug ID: 51254
           Summary: can't include cxxabi.h using libstdc++ ABI with libc++
           Product: libc++
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: john at jmdtech.org
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com

Created attachment 25085
  --> https://bugs.llvm.org/attachment.cgi?id=25085&action=edit
fix for missing abi header

This might be partially a dup of https://bugs.llvm.org/show_bug.cgi?id=22445,
but that was already resolved. Based on that bug,
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61728 looks related as well.

I'm trying to build a toolchain with clang and libc++ where libc++ uses the
libstdc++ ABI. Two issues arose:

1. CMake configuration is missing an ABI header that was added in gcc 8
(cxxabi_init_exception.h)
2. libstdc++'s cxxabi.h uses implementation details from libstdc++'s typeinfo
header, which is incompatible with libc++'s typeinfo header.

More details following--

I built the toolchain using:

cmake -G Ninja -DLLVM_ENABLE_PROJECTS='clang;libcxx;clang-tools-extra;lld'
-DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/tmp/clang-install
-DLIBCXX_CXX_ABI=libstdc++ -DLLVM_TARGETS_TO_BUILD="X86" ../llvm

Building and installing the toolchain itself works fine. Attempting to use
clang with libc++ to compile a source file that simply includes the <cxxabi.h>
header fails, however:

```
#include <cxxabi.h>
```

$ clang++ -stdlib=libc++ -c -o abi /tmp/abi.cpp

results in:

In file included from /tmp/abi.cpp:1:
/tmp/clang-install/bin/../include/c++/v1/cxxabi.h:52:10: fatal error:
'bits/cxxabi_init_exception.h' file not found
#include <bits/cxxabi_init_exception.h>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

----------------------------------------

I've attached a diff that copies the appropriate header. Using the fix,
however, still results in the following:

In file included from /tmp/abi.cpp:1:
/tmp/clang-install/bin/../include/c++/v1/cxxabi.h:308:23: error: no member
named '__do_catch' in 'std::type_info'
    return __pointee->__do_catch (thrown_type->__pointee, thr_obj, outer + 2);
           ~~~~~~~~~  ^
1 error generated.

----------------------------------------

If you'd rather me submit a PR with the diff to fix the missing header, I can
do that. As for the cxxabi.h file from gcc, it seems to be using implementation
details from their <typeinfo> header which is related to the gcc bug I linked
above. Is this something that should be worked around in libc++, or should I
file a gcc bug so they can fix their cxxabi.h header to not depend on their own
<typeinfo> implementation?

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20210728/f227908a/attachment.html>