Clang: Avoid consuming gcc internal include paths

Given the (default) include paths of GCC, e.g.

 /usr/include/c++/7
 /usr/include/x86_64-linux-gnu/c++/7
 /usr/include/c++/7/backward
 /usr/lib/gcc/x86_64-linux-gnu/7/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/7/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include

discard gcc-internal paths like /usr/lib/gcc/x86_64-linux-gnu/7/include
as they are not relevant for clang and even confuse it with regard to
 #include_next.

Paths below the gcc install dir are considered as gcc-internal. The
install dir is queried with

  $ gcc -print-search-dirs

Some GCC distributions, like MinGW, ship the standard library headers in
the install dir. Ensure to not discard these.

Fixes: QTCREATORBUG-22898
Change-Id: Ia85258fb01b72ad073e71390e003fe8268e3b01f
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/plugins/projectexplorer/gcctoolchain.cpp b/src/plugins/projectexplorer/gcctoolchain.cpp
index 8c1c9e2952b..e7616473986 100644
--- a/src/plugins/projectexplorer/gcctoolchain.cpp
+++ b/src/plugins/projectexplorer/gcctoolchain.cpp
@@ -232,6 +232,23 @@ static QString gccVersion(const FilePath &path, const QStringList &env)
     return QString::fromLocal8Bit(runGcc(path, arguments, env)).trimmed();
 }
 
+static Utils::FilePath gccInstallDir(const FilePath &path, const QStringList &env)
+{
+    const QStringList arguments("-print-search-dirs");
+    QString output = QString::fromLocal8Bit(runGcc(path, arguments, env)).trimmed();
+    // Expected output looks like this:
+    //   install: /usr/lib/gcc/x86_64-linux-gnu/7/
+    //   ...
+    // Note that clang also supports "-print-search-dirs". However, the
+    // install dir is not part of the output (tested with clang-8/clang-9).
+
+    const QString prefix = "install: ";
+    const QString line = QTextStream(&output).readLine();
+    if (!line.startsWith(prefix))
+        return {};
+    return Utils::FilePath::fromString(QDir::cleanPath(line.mid(prefix.size())));
+}
+
 // --------------------------------------------------------------------------
 // GccToolChain
 // --------------------------------------------------------------------------
@@ -269,6 +286,15 @@ void GccToolChain::setOriginalTargetTriple(const QString &targetTriple)
     toolChainUpdated();
 }
 
+void GccToolChain::setInstallDir(const Utils::FilePath &installDir)
+{
+    if (m_installDir == installDir)
+        return;
+
+    m_installDir = installDir;
+    toolChainUpdated();
+}
+
 QString GccToolChain::defaultDisplayName() const
 {
     QString type = typeDisplayName();
@@ -310,6 +336,13 @@ QString GccToolChain::version() const
     return m_version;
 }
 
+FilePath GccToolChain::installDir() const
+{
+    if (m_installDir.isEmpty())
+        m_installDir = detectInstallDir();
+    return m_installDir;
+}
+
 void GccToolChain::setTargetAbi(const Abi &abi)
 {
     if (abi == m_targetAbi)
@@ -715,6 +748,7 @@ void GccToolChain::resetToolChain(const FilePath &path)
     const DetectedAbisResult detectedAbis = detectSupportedAbis();
     m_supportedAbis = detectedAbis.supportedAbis;
     m_originalTargetTriple = detectedAbis.originalTargetTriple;
+    m_installDir = installDir();
 
     m_targetAbi = Abi();
     if (!m_supportedAbis.isEmpty()) {
@@ -856,6 +890,13 @@ QString GccToolChain::detectVersion() const
     return gccVersion(findLocalCompiler(m_compilerCommand, env), env.toStringList());
 }
 
+Utils::FilePath GccToolChain::detectInstallDir() const
+{
+    Environment env = Environment::systemEnvironment();
+    addToEnvironment(env);
+    return gccInstallDir(findLocalCompiler(m_compilerCommand, env), env.toStringList());
+}
+
 // --------------------------------------------------------------------------
 // GccToolChainFactory
 // --------------------------------------------------------------------------
@@ -1119,6 +1160,9 @@ QList<ToolChain *> GccToolChainFactory::autoDetectToolChain(const ToolChainDescr
     const GccToolChain::DetectedAbisResult detectedAbis = guessGccAbi(localCompilerPath,
                                                                       systemEnvironment.toStringList(),
                                                                       macros);
+    const Utils::FilePath installDir = gccInstallDir(localCompilerPath,
+                                                     systemEnvironment.toStringList());
+
     for (const Abi &abi : detectedAbis.supportedAbis) {
         std::unique_ptr<GccToolChain> tc(dynamic_cast<GccToolChain *>(create()));
         if (!tc)
@@ -1134,6 +1178,7 @@ QList<ToolChain *> GccToolChainFactory::autoDetectToolChain(const ToolChainDescr
         tc->setSupportedAbis(detectedAbis.supportedAbis);
         tc->setTargetAbi(abi);
         tc->setOriginalTargetTriple(detectedAbis.originalTargetTriple);
+        tc->setInstallDir(installDir);
         tc->setDisplayName(tc->defaultDisplayName()); // reset displayname
         if (!checker || checker(tc.get()))
             result.append(tc.release());
@@ -1192,6 +1237,7 @@ void GccToolChainConfigWidget::applyImpl()
         tc->setSupportedAbis(m_abiWidget->supportedAbis());
         tc->setTargetAbi(m_abiWidget->currentAbi());
     }
+    tc->setInstallDir(tc->detectInstallDir());
     tc->setOriginalTargetTriple(tc->detectSupportedAbis().originalTargetTriple);
     tc->setDisplayName(displayName); // reset display name
     tc->setPlatformCodeGenFlags(splitString(m_platformCodeGenFlagsLineEdit->text()));