gcc10 missing header <wchar.h>

[haberg-1]

When installing gcc10 and compiling externally with /opt/local/bin/g++-mp-10 the error below appears, possibly because system headers that GCC relies on, have on MacOS 10.5 been moved away from /usr/include/.

In file included from /opt/local/include/gcc10/c++/bits/postypes.h:40,
                 from /opt/local/include/gcc10/c++/iosfwd:40,
                 from /opt/local/include/gcc10/c++/ios:38,
                 from /opt/local/include/gcc10/c++/ostream:38,
                 from /opt/local/include/gcc10/c++/iostream:39,
                 from c++version.cc:2:
/opt/local/include/gcc10/c++/cwchar:44:10: fatal error: wchar.h: No such file or directory
   44 | #include <wchar.h>
      |          ^~~~~~~~~
compilation terminated.

[cjones051073 (Chris Jones)]

Yes, this is likely due to the removal of /usr/include

Like clang, gcc now respects your SDKROOT setting, so this is the recommendation now. i.e.

export SDKROOT=`xcrun --show-sdk-path`

then you should be fine.

 > cat test.cpp
#include <wchar.h>
#include <iostream>
int main() {
  wchar_t a = 99;
  std::cout << "Test " << a << std::endl;
  return 0;
}
 > g++-mp-10 ./test.cpp
 > ./a.out 
Test 99

Another option is to install the command line tools package.

[cjones051073 (Chris Jones)]

b.t.w. another option is to run your compilation through xcrun. e.g.

 > xcrun g++-mp-10 ./test.cpp

[haberg-1]

Yes, I am aware of those variations, but gcc9 and clang-10 work without that, so you might check what they do. And the command line tools package does not help here, as /usr/include/ does not exist.

[cjones051073 (Chris Jones)]

The command line tools package does not install to /usr/include. Instead it installs SDKs to /Library/Developer/CommandLineTools

I see no difference in the behaviour or content of gcc10, compared to gcc9.

Oberon ~/Downloads > port contents gcc9 | grep wchar    
  /opt/local/include/gcc9/c++/cwchar
  /opt/local/include/gcc9/c++/tr1/cwchar
  /opt/local/include/gcc9/c++/tr1/wchar.h
Oberon ~/Downloads > port contents gcc10 | grep wchar
  /opt/local/include/gcc10/c++/cwchar
  /opt/local/include/gcc10/c++/tr1/cwchar
  /opt/local/include/gcc10/c++/tr1/wchar.h
Oberon ~/Downloads > port contents libgcc10 | grep wchar
  /opt/local/include/gcc/c++/cwchar
  /opt/local/include/gcc/c++/tr1/cwchar
  /opt/local/include/gcc/c++/tr1/wchar.h

Please test build the example application I posted above, using the -H option, and compare to the logs I attached above.

[cjones051073 (Chris Jones)]

Note, the logs I attached above or *without* setting SDKROOT, or using xcrun. Its what I get out-the-box just using

g++-mp-10 -H test.cpp

etc.

[haberg-1]

It gives compilation error:

% /opt/local/bin/g++-mp-10 test.cpp -o test test.cpp:1:10: fatal error: wchar.h: No such file or directory

1 | #include <wchar.h>

|

compilation terminated.

[haberg-1]

I also get the same error with gcc9, as below. However, it works with clang-10: the issue arose with the binary at ​https://llvm.org, fixable by the same workaround, but somehow, you have fixed it.

--

% /opt/local/bin/g++-mp-9 test.cpp -o test

test.cpp:1:10: fatal error: wchar.h: No such file or directory

1 | #include <wchar.h>

|

compilation terminated.

--

% /opt/local/bin/clang++-mp-10 test.cpp -o test

<no diagnostic>

--

[cjones051073 (Chris Jones)]

Run build with the -v option. That will tell you agmonst other things the search paths the compiler is using to find headers.

 > g++-mp-10 -v test.cpp
<snip>
#include <...> search starts here:
 /opt/local/include/gcc10/c++/
 /opt/local/include/gcc10/c++//x86_64-apple-darwin19
 /opt/local/include/gcc10/c++//backward
 /opt/local/lib/gcc10/gcc/x86_64-apple-darwin19/10.1.0/include
 /opt/local/lib/gcc10/gcc/x86_64-apple-darwin19/10.1.0/include-fixed
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks
End of search list.
<snip>

Do you have the CLT installed ? i.e. what is in

 > ls -l /Library/Developer/CommandLineTools/SDKs/
total 0
lrwxr-xr-x  1 root  wheel   15 16 Apr 12:53 MacOSX.sdk -> MacOSX10.15.sdk
drwxr-xr-x  7 root  wheel  224 16 Apr 12:53 MacOSX10.14.sdk
drwxr-xr-x  8 root  wheel  256 16 Apr 12:53 MacOSX10.15.sdk

Bottom line is, with the removal of /usr/include, you have to do *something* to instruct the compiler where to find the SDK to use.

• define SDKROOT
• use xcrun
• pass the -sysroot /path/to/SDK compiler flag
• install the CLT package

[haberg-1]

It works after running 'xcode-select —install', both gcc9 and gcc10. I had it installed before, but perhaps it was lost in some update; a working compiler in /usr/bin/clang++, though. Before, I had bin/ in /Library/Developer/CommandLineTools/usr/, but not include/, which is now present. Also, gcc9 may have worked before, but not after removing and reinstalling. But clang-10 worked, so it may be different in this respect.

[cjones051073 (Chris Jones)]

Sounds like you perhaps ran into something like

​https://trac.macports.org/wiki/ProblemHotlist#reinstall-clt

For that port should have given you some warnings and directed you to the above site.

Anyway, glad you have sorted your problem out.

[haberg-1]

Some installed stuff seemed to missing such as /Library/Developer/CommandLineTools/usr/include/, and I did not get any complaints about that from MacPorts. It would be great if one can somehow can get a reminder to run 'xcode-select —install'.