cpp_clang.cpp:(.text+0x4d1): undefined reference to `llvm::vfs::getRealFileSystem()'

jiapei100

Hi, all:

I'm working under Ubuntu 22.04,

➜  build lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.2 LTS
Release:	22.04
Codename:	jammy
➜  build gcc --version
gcc (Ubuntu 11.3.0-1ubuntu1~22.04.1) 11.3.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I failed to build Qt6 with the following ERROR messages . It looks the faults are related to LLVM ???

So, my questions:

To build Qt6, must I use clang rather than gcc ?
How come Qt6 got an ERROR related to llvm::vfs???

I actually failed to build qttools, which in the end, let me remove 3 packages out from building:

qttools
qtdoc
qttranslations

and, I did find the connection between qt6 and llvm, out of my expectation. I've been thinking even the tools, qt6 itself should have NOTHING to do with llvm. These two packages should have NO dependency relationship.

➜  qttools grep -rwn "llvm"
configure.cmake:120:Either set CMAKE_PREFIX_PATH or LLVM_INSTALL_DIR to the location of your llvm installation.
configure.cmake:122:On macOS, you can use Homebrew's llvm package.
tests/auto/qdoc/catch/catch.hpp:339:         // work around clang bug with libstdc++ https://bugs.llvm.org/show_bug.cgi?id=31852
src/linguist/lupdate/lupdatepreprocessoraction.cpp:19:    llvm::StringRef fileName = sm.getFilename(sourceRange.getBegin());
src/linguist/lupdate/lupdatepreprocessoraction.cpp:138:    llvm::StringRef fileName = sm.getFilename(sourceRange.getBegin());
src/linguist/lupdate/lupdatepreprocessoraction.cpp:145:    llvm::StringRef skippedText = llvm::StringRef(begin, end - begin);
src/linguist/lupdate/clangtoolastreader.h:97:        clang::CompilerInstance &compiler, llvm::StringRef /* inFile */) override
src/linguist/lupdate/cpp_clang.cpp:246:    return [=](const clang::tooling::CommandLineArguments &args, llvm::StringRef /*unused*/) {
src/linguist/lupdate/cpp_clang.cpp:275:        clang::tooling::CommandLineArguments::iterator it = llvm::find(adjustedArgs, "--");
src/linguist/lupdate/cpp_clang.cpp:281:bool ClangCppParser::stringContainsTranslationInformation(llvm::StringRef ba)
src/linguist/lupdate/cpp_clang.cpp:285:    constexpr llvm::StringLiteral qDeclareTrFunction("Q_DECLARE_TR_FUNCTIONS(");
src/linguist/lupdate/cpp_clang.cpp:286:    constexpr llvm::StringLiteral qtTrNoop("QT_TR_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:287:    constexpr llvm::StringLiteral qtTrNoopUTF8("QT_TR_NOOP)UTF8(");
src/linguist/lupdate/cpp_clang.cpp:288:    constexpr llvm::StringLiteral qtTrNNoop("QT_TR_N_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:289:    constexpr llvm::StringLiteral qtTrIdNoop("QT_TRID_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:290:    constexpr llvm::StringLiteral qtTrIdNNoop("QT_TRID_N_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:291:    constexpr llvm::StringLiteral qtTranslateNoop("QT_TRANSLATE_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:292:    constexpr llvm::StringLiteral qtTranslateNoopUTF8("QT_TRANSLATE_NOOP_UTF8(");
src/linguist/lupdate/cpp_clang.cpp:293:    constexpr llvm::StringLiteral qtTranslateNNoop("QT_TRANSLATE_N_NOOP(");
src/linguist/lupdate/cpp_clang.cpp:294:    constexpr llvm::StringLiteral qtTranslateNoop3("QT_TRANSLATE_NOOP3(");
src/linguist/lupdate/cpp_clang.cpp:295:    constexpr llvm::StringLiteral qtTranslateNoop3UTF8("QT_TRANSLATE_NOOP3_UTF8(");
src/linguist/lupdate/cpp_clang.cpp:296:    constexpr llvm::StringLiteral qtTranslateNNoop3("QT_TRANSLATE_N_NOOP3(");
src/linguist/lupdate/cpp_clang.cpp:297:    constexpr llvm::StringLiteral translatorComment("TRANSLATOR ");
src/linguist/lupdate/cpp_clang.cpp:298:    constexpr llvm::StringLiteral qtTrId("qtTrId(");
src/linguist/lupdate/cpp_clang.cpp:299:    constexpr llvm::StringLiteral tr("tr(");
src/linguist/lupdate/cpp_clang.cpp:300:    constexpr llvm::StringLiteral trUtf8("trUtf8(");
src/linguist/lupdate/cpp_clang.cpp:301:    constexpr llvm::StringLiteral translate("translate(");
src/linguist/lupdate/cpp_clang.cpp:304:    const auto baSliced = ba.slice(pos, llvm::StringRef::npos);
src/linguist/lupdate/cpp_clang.cpp:305:     if (pos != llvm::StringRef::npos) {
src/linguist/lupdate/clangtoolastreader.cpp:24:            clang::StringLiteral *stringLit = llvm::dyn_cast_or_null<clang::StringLiteral>(child);
src/linguist/lupdate/clangtoolastreader.cpp:53:            clang::AccessSpecDecl *accessSpec = llvm::dyn_cast<clang::AccessSpecDecl>(decl);
src/linguist/lupdate/clangtoolastreader.cpp:54:            clang::CXXMethodDecl *method = llvm::dyn_cast<clang::CXXMethodDecl>(decl);
src/linguist/lupdate/clangtoolastreader.cpp:161:                clang::CXXRecordDecl *recordDecl = llvm::dyn_cast<clang::CXXRecordDecl>(decl);
src/linguist/lupdate/clangtoolastreader.cpp:195:            llvm::raw_string_ostream tmp(context);
src/linguist/lupdate/clangtoolastreader.cpp:220:    bool hasQuote(llvm::StringRef source)
src/linguist/lupdate/clangtoolastreader.cpp:225:    bool trFunctionPresent(llvm::StringRef text)
src/linguist/lupdate/clangtoolastreader.cpp:227:        if (text.contains(llvm::StringRef("qtTrId(")))
src/linguist/lupdate/clangtoolastreader.cpp:229:        if (text.contains(llvm::StringRef("tr(")))
src/linguist/lupdate/clangtoolastreader.cpp:231:        if (text.contains(llvm::StringRef("trUtf8(")))
src/linguist/lupdate/clangtoolastreader.cpp:233:        if (text.contains(llvm::StringRef("translate(")))
src/linguist/lupdate/clangtoolastreader.cpp:235:        if (text.contains(llvm::StringRef("Q_DECLARE_TR_FUNCTIONS(")))
src/linguist/lupdate/clangtoolastreader.cpp:237:        if (text.contains(llvm::StringRef("QT_TR_N_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:239:        if (text.contains(llvm::StringRef("QT_TRID_N_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:241:        if (text.contains(llvm::StringRef("QT_TRANSLATE_N_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:243:        if (text.contains(llvm::StringRef("QT_TRANSLATE_N_NOOP3(")))
src/linguist/lupdate/clangtoolastreader.cpp:245:        if (text.contains(llvm::StringRef("QT_TR_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:247:        if (text.contains(llvm::StringRef("QT_TRID_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:249:        if (text.contains(llvm::StringRef("QT_TRANSLATE_NOOP(")))
src/linguist/lupdate/clangtoolastreader.cpp:251:        if (text.contains(llvm::StringRef("QT_TRANSLATE_NOOP3(")))
src/linguist/lupdate/clangtoolastreader.cpp:253:        if (text.contains(llvm::StringRef("QT_TR_NOOP_UTF8(")))
src/linguist/lupdate/clangtoolastreader.cpp:255:        if (text.contains(llvm::StringRef("QT_TRANSLATE_NOOP_UTF8(")))
src/linguist/lupdate/clangtoolastreader.cpp:257:        if (text.contains(llvm::StringRef("QT_TRANSLATE_NOOP3_UTF8(")))
src/linguist/lupdate/clangtoolastreader.cpp:370:        llvm::raw_string_ostream temp(arguments[i]);
src/linguist/lupdate/clangtoolastreader.cpp:564:        llvm::StringRef text(buffer + commentEndDecomp.second,
src/linguist/lupdate/clangtoolastreader.cpp:569:        if (text.find_first_of(";}#@") != llvm::StringRef::npos) {
src/linguist/lupdate/clangtoolastreader.cpp:574:        if (sameLineComment && text.find_first_of(",") != llvm::StringRef::npos) {
src/linguist/lupdate/cpp_clang.h:21:#include <llvm/ADT/StringRef.h>
src/linguist/lupdate/cpp_clang.h:36:inline QString toQt(llvm::StringRef str)
src/linguist/lupdate/cpp_clang.h:245:    inline QString cleanQuote(llvm::StringRef s, QuoteCompulsary quote)
src/linguist/lupdate/cpp_clang.h:308:    bool stringContainsTranslationInformation(llvm::StringRef ba);
src/qdoc/clangcodeparser.cpp:988:    // llvm to expose some of the C++ API methods that would
src/qdoc/doc/qdoc-guide/qdoc-guide.qdoc:23:    \note \l{QDoc Manual}{QDoc} requires \l{http://clang.llvm.org}{Clang}
src/qdoc/doc/qdoc-guide/qdoc-guide.qdoc:641:    \l {https://llvm.org/}{the LLVM Compiler Infrastructure Project}.
src/qdoc/doc/qdoc-guide/qdoc-guide.qdoc:643:    \l{http://clang.llvm.org}{Clang 8.0} or later.
src/qdoc/doc/qdoc-guide/qdoc-guide.qdoc:659:        \l{https://formulae.brew.sh/formula/llvm}{llvm formula}.
src/qdoc/doc/qdoc-guide/qdoc-guide.qdoc:662:    \note the prebuilt binaries from \l{http://releases.llvm.org/download.html}
src/assistant/qlitehtml/.clang-format:14:# [2] https://clang.llvm.org/docs/ClangFormatStyleOptions.html

Anyway.... Now, successfully built after removing the above 3 packages from building.
Well, of course, don't forget to NOT use the to-be-deprecated FileDescriptor::SYNTAX_PROTO3:

/*** going to be deprecated.
    if (file->syntax() != FileDescriptor::SYNTAX_PROTO3) {
        *error = "Invalid proto used. qtprotobufgen only supports 'proto3' syntax";
        return false;
    }
***/

Cheers

SGaist

Hi,

llvm is used for QDoc to parse and analyse client code. It's not related to the compilation of Qt itself where you can use gcc or clang based on your preference and its availability.