Bug 360074

Summary:	Include paths detected wrongly with clang and libc++
Product:	[Applications] kdevelop	Reporter:	John <john5342>
Component:	Language Support: CPP (Clang-based)	Assignee:	kdevelop-bugs-null
Status:	REPORTED ---
Severity:	normal
Priority:	NOR
Version First Reported In:	4.90.91
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description John 2016-03-04 14:53:55 UTC

When i use clang with libc++, KDevelop still uses the libstdc++ headers causing all kinds of problems with library types that aren't yet included in libstdc++.

After an initial investigation i am guessing the include paths are discovered from GccLikeCompiler::includes. Unfortunately using "clang++ -E -v" only shows the default settings that clang was compiled with, which is the libstdc++ setup.

Using "clang++ -Wp,-v" however shows the include paths that are actually used. The same options also work for g++ too. The only problem is that it then expects an input file so i would suggest "clang++ -Wp,-v dummy.cpp -fsyntax-only"

Reproducible: Always

Comment 1 Milian Wolff 2016-03-04 20:07:17 UTC

I think you just need to pass `-stdlib=libc++` to the compiler from the compiler settings dialog. That should - hopefully - work.

I'll keep this bug open, as we should make it simpler to switch between the libs, and potentially read that data from CMake directly, if possible.

Comment 2 John 2016-03-04 21:41:46 UTC

I am not using CMake.

I already am adding -stdlib=libc++ to the parser command line (Right click project -> Open Configuration -> Language support -> C/C++ Parser and setting a custom profile with -stdlib=libc++).

I think the problem is simply that clang returns the wrong details with -E -v. Note the warning about not using the the stdlib argument.

[john@aglap ~]$ clang++ -E -v
clang version 3.7.1 (tags/RELEASE_371/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Selected GCC installation: /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

[john@aglap ~]$ clang++ -E -v -stdlib=libc++
clang version 3.7.1 (tags/RELEASE_371/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Selected GCC installation: /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
clang-3.7: warning: argument unused during compilation: '-stdlib=libc++'

[john@aglap ~]$ clang++ -Wp,-v dummy.cpp -fsyntax-only
clang -cc1 version 3.7.1 based upon LLVM 3.7.1 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0/../../../../include/c++/5.3.0
 /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0/../../../../include/c++/5.3.0/x86_64-unknown-linux-gnu
 /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/5.3.0/../../../../include/c++/5.3.0/backward
 /usr/local/include
 /usr/bin/../lib/clang/3.7.1/include
 /usr/include
End of search list.

[john@aglap ~]$ clang++ -Wp,-v dummy.cpp -fsyntax-only -stdlib=libc++
clang -cc1 version 3.7.1 based upon LLVM 3.7.1 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/bin/../include/c++/v1
 /usr/local/include
 /usr/bin/../lib/clang/3.7.1/include
 /usr/include
End of search list.

Comment 3 John 2016-03-04 21:45:13 UTC

My apologies. It is still not working, although i may well be completely wrong about the cause of the problem because if the detection is through GccLikeCompiler::includes, then i don't think it would succeed at parsing any of the -E -v output anyway because it doesn't match what the code is looking for.

Comment 4 Milian Wolff 2016-03-04 22:47:39 UTC

Your command is wrong/incomplete:

clang++ -std=c++11 -xc++ -dM -E -v /dev/null

vs

clang++ -std=c++11 -stdlib=libc++ -xc++ -dM -E -v /dev/null

I get different output as expected.

Comment 5 Justin Zobel 2021-03-09 22:48:53 UTC

Thank you for the bug report.

As this report hasn't seen any changes in 5 years or more, we ask if you can please confirm that the issue still persists.

If this bug is no longer persisting or relevant please change the status to resolved.