Build Qt fails - can't locate libclang

KeithS

Trying to build Qt6.4.3 from source. I have followed the docs and installed Perl, Python, Cmake, Ninja, Node.js, OpenSSL and LLVM.

LLVM version 16 was installed at C:\Program Files\LLVM and the env var LLVM_INSTALL_DIR set to this directory. Also LLVM_INSTALL_DIR\bin was added to the PATH, and I have checked that clang.exe is found.

The configure script is then

configure -prefix C:\Qt\6.4.3-x64 -confirm-license -commercial -debug-and-release -mp -opengl desktop -openssl-runtime OPENSSL_INCDIR="C:\Program Files\OpenSSL-Win64\include" -mp -nomake tests -nomake examples

This all runs and has no errors apart from the final woraning "WARNING: QDoc will not be compiled, probably because libclang could not be located. "

So I'm baffled as to what is wrong/missing. Anyone else built Qt6 from source successfully?

Keith

jsulm

@KeithS Do you have libclang? Check the config.log file to get more information about the issue.

KeithS

@jsulm There is a libclang.lib:

C:\Program Files\LLVM\lib>ll
total 1085
-rw-rw-rw- 1 user group 135462 Mar 19 22:43 libomp.lib
-rw-rw-rw- 1 user group 15782 Mar 19 22:44 LTO.lib
-rw-rw-rw- 1 user group 78492 Mar 19 22:47 libclang.lib
-rw-rw-rw- 1 user group 5654 Mar 19 22:48 Remarks.lib
-rw-rw-rw- 1 user group 229258 Mar 19 22:48 LLVM-C.lib
-rw-rw-rw- 1 user group 643268 Mar 19 22:48 liblldb.lib
drwxrwxrwx 1 user group 0 Mar 30 12:00 clang
drwxrwxrwx 1 user group 0 Mar 30 12:00 libear
drwxrwxrwx 1 user group 0 Mar 30 12:00 cmake
drwxrwxrwx 1 user group 0 Mar 30 12:00 site-packages
drwxrwxrwx 1 user group 0 Mar 30 12:00 libscanbuild

There does not seem to be any config.log in the installation directory?

jsulm

@KeithS said in Build Qt fails - can't locate libclang:

There does not seem to be any config.log in the installation directory?

It is in the folder from which you called configure...

You also should avoid using folders with spaces.

KeithS

@jsulm I don't have a directory called configure inthe Qt build directory (there is a file called configure, and a directory called config.tests).

R.e. directory names with spaces, that's Windows for you - C:\Program Files and C:\Program Files (x86).

Thing is, it did work in the past for Qt 5.15.x - QDoc would find clang using the same installation. BUt then the Qt folks seem to break things with every new release, sigh.

jsulm

@KeithS said in Build Qt fails - can't locate libclang:

I don't have a directory called configure

I did not write anything about folder called "configure". I'm talking about folder in which you were when you called configure (build folder):

cd SOME_FOLDER
configure ...

"that's Windows for you" - doesn't stop you from installing into other folders, just like Qt does...

KeithS

@jsulm Ah sorry I misunderstood you. The directory that 'configure' was run in does not have a config.log:

C:\Qt\qt-everywhere-src-6.4.3>ls config*
config.opt configure configure_windows_64.bat
config.opt.in configure.bat
config.summary configure.json

config.tests=:
assimp linux_v4l socketcan
bluez no_direct_extern_access socketcan_fd
bluez_le precompile_header winrt_bt
evr qt3d_fbxsdk winrt_geolocation
gpu_vivante quick3d_assimp winrt_sensors
linux_crypto_api separate_debug_info wmsdk

In regard to LLVM, perhaps something in Qt has broken since 5.15 installer and it indeed doesn't like spaces in directory names. OK so I'll try 'C:\PROGRA~1\LLVM' which translates to the same path with long names.

KeithS

...Using short names for the LLVM_INSTALL_DIR gave exactly the same result - clang missing:

Configuring submodule 'qttools'
-- Could NOT find Clang (missing: Clang_DIR)
-- Could NOT find Clang (missing: Clang_DIR)
....
WARNING: QDoc will not be compiled, probably because libclang could not be located. This means that you cannot build the Qt documentation.
Either set CMAKE_PREFIX_PATH or LLVM_INSTALL_DIR to the location of your llvm installation.
On Linux systems, you may be able to install libclang by installing the libclang-dev or libclang-devel package, depending on your distribution.
On macOS, you can use Homebrew's llvm package.
You will also need to set the FEATURE_clang CMake variable to ON to re-evaluate this check.
WARNING: Clang-based lupdate parser will not be available. LLVM and Clang C++ libraries have not been found.
You will need to set the FEATURE_clangcpp CMake variable to ON to re-evaluate this check.

wssddc

I know this is an old thread, but I see the same problem building Qt 5.15.10 from source. It works with LLVM 15.06, but can't build QDoc with LLVM 16.06. (Windows 10, 64-bit). I got LLVM binaries from https://github.com/llvm/llvm-project/releases, not from Qt.

Johnson III

Me too. And there is a links :
https://bugreports.qt.io/browse/QTBUG-81214