[llvm-bugs] [Bug 44475] New: compiler-rt complains unnecessarily about missing C++ headers on macOS

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44475

            Bug ID: 44475
           Summary: compiler-rt complains unnecessarily about missing C++
                    headers on macOS
           Product: compiler-rt
           Version: unspecified
          Hardware: Macintosh
                OS: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: compiler-rt
          Assignee: unassignedbugs at nondot.org
          Reporter: steven at uplinklabs.net
                CC: llvm-bugs at lists.llvm.org

It seems really strange that compiler-rt's
cmake/Modules/CompilerRTCompile.cmake complains about C++ headers being missing
on macOS, when the build in question is happening in a full git clone of the
llvm-project tree, and "libcxx;libcxxabi" are present in LLVM_ENABLE_PROJECTS
for the build.

The message recommends pursuing a manual step of running "installheaders" in
libcxx. Couldn't that be replaced by a build step when libcxx/libcxxabi are
part of the build?


The output in question:

---
[6289/6380] Checking that just-built clang can find C++ headers...
FAILED:
projects/compiler-rt/lib/sanitizer_common/tests/CMakeFiles/CompilerRTUnitTestCheckCxx 
cd
/Users/steven/dev/llvm/build/llvm/projects/compiler-rt/lib/sanitizer_common/tests
&& bash -c "echo '#include <iostream>' |
/Users/steven/dev/llvm/build/llvm/./bin/clang
-isysroot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk
-E -x c++ - > /dev/null;if [ \$? != 0 ] ;  then echo;  echo 'Your just-built
clang cannot find C++ headers, which are needed to build and run compiler-rt
tests.';  echo 'You should copy or symlink your system C++ headers into
/Users/steven/dev/llvm/build/llvm/include/c++';  if [ -d \$(dirname \$(dirname
\$(xcrun -f clang)))/include/c++ ];    then echo 'e.g. with:';    echo '  cp
-r' \$(dirname \$(dirname \$(xcrun -f clang)))/include/c++
'/Users/steven/dev/llvm/build/llvm/include/';  elif [ -d \$(dirname \$(dirname
\$(xcrun -f clang)))/lib/c++ ];    then echo 'e.g. with:';    echo '  cp -r'
\$(dirname \$(dirname \$(xcrun -f clang)))/lib/c++
'/Users/steven/dev/llvm/build/llvm/include/';  fi;  echo 'This can also be
fixed by checking out the libcxx project from llvm.org and installing the
headers';  echo 'into your build directory:';  echo '  cd
/Users/steven/dev/llvm/llvm-project/llvm/projects && svn co
http://llvm.org/svn/llvm-project/libcxx/trunk libcxx';  echo '  cd
/Users/steven/dev/llvm/build/llvm && make -C
/Users/steven/dev/llvm/llvm-project/llvm/projects/libcxx installheaders
HEADER_DIR=/Users/steven/dev/llvm/build/llvm/include';  echo;  false;fi"
<stdin>:1:10: fatal error: 'iostream' file not found
#include <iostream>
         ^~~~~~~~~~
1 error generated.

Your just-built clang cannot find C++ headers, which are needed to build and
run compiler-rt tests.
You should copy or symlink your system C++ headers into
/Users/steven/dev/llvm/build/llvm/include/c++
e.g. with:
  cp -r
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++
/Users/steven/dev/llvm/build/llvm/include/
This can also be fixed by checking out the libcxx project from llvm.org and
installing the headers
into your build directory:
  cd /Users/steven/dev/llvm/llvm-project/llvm/projects && svn co
http://llvm.org/svn/llvm-project/libcxx/trunk libcxx
  cd /Users/steven/dev/llvm/build/llvm && make -C
/Users/steven/dev/llvm/llvm-project/llvm/projects/libcxx installheaders
HEADER_DIR=/Users/steven/dev/llvm/build/llvm/include

ninja: build stopped: subcommand failed.
---

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