qdoc: Query the compiler for system and framework include paths on macOS

Depending on the version, libclang is not able to resolve the system
include paths on macOS; Fetch the include paths from the compiler by
calling 'clang++ -E -x c++ - -v', parsing the output, and passing them
as additional arguments when parsing the sources.

Note that this requires the correct version of the compiler to be
available under PATH.

Fixes: QTBUG-94365
Change-Id: Iaa1b9869d3be0b4fcb8df00b47bb43a80032aa02
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

3 files changed, 109 insertions, 1 deletions

diff --git a/src/qdoc/clangcodeparser.cpp b/src/qdoc/clangcodeparser.cpp
index f037e4ed8..46c237114 100644
--- a/src/qdoc/clangcodeparser.cpp
+++ b/src/qdoc/clangcodeparser.cpp
@@ -1088,14 +1088,22 @@ Node *ClangVisitor::nodeForCommentAtLocation(CXSourceLocation loc, CXSourceLocat
   Get the include paths from the qdoc configuration database
   \a config. Call the initializeParser() in the base class.
   Get the defines list from the qdocconf database.
+
+  \note on \macos, we try to also query the system/framework
+  include paths from the compiler.
  */
 void ClangCodeParser::initializeParser()
 {
     Config &config = Config::instance();
     m_version = config.getString(CONFIG_VERSION);
-    const auto args = config.getStringList(CONFIG_INCLUDEPATHS);
+    auto args = config.getStringList(CONFIG_INCLUDEPATHS);
     QSet<QString> seen;
     m_includePaths.clear();
+
+#ifdef Q_OS_MACOS
+    args.append(Utilities::getInternalIncludePaths(QStringLiteral("clang++")));
+#endif
+
     // Remove empty paths and duplicates and add -I and canonicalize if necessary
     for (const auto &p : args) {
         QByteArray option;
diff --git a/src/qdoc/utilities.cpp b/src/qdoc/utilities.cpp
index 19e1572f6..f82282b9b 100644
--- a/src/qdoc/utilities.cpp
+++ b/src/qdoc/utilities.cpp
@@ -26,6 +26,7 @@
 **
 ****************************************************************************/
 
+#include <QtCore/qprocess.h>
 #include "utilities.h"
 
 QT_BEGIN_NAMESPACE
@@ -102,6 +103,104 @@ QString comma(qsizetype wordPosition, qsizetype numberOfWords)
     return QStringLiteral(", and ");
 }
 
+/*!
+    \internal
+*/
+static bool runProcess(const QString &program, const QStringList &arguments,
+                       QByteArray *stdOutIn, QByteArray *stdErrIn)
+{
+    QProcess process;
+    process.start(program, arguments, QProcess::ReadWrite);
+    if (!process.waitForStarted()) {
+        qCDebug(lcQdoc).nospace() << "Unable to start " << process.program()
+                                  << ": " << process.errorString();
+        return false;
+    }
+    process.closeWriteChannel();
+    const bool finished = process.waitForFinished();
+    const QByteArray stdErr = process.readAllStandardError();
+    if (stdErrIn)
+        *stdErrIn = stdErr;
+    if (stdOutIn)
+        *stdOutIn = process.readAllStandardOutput();
+
+    if (!finished) {
+        qCDebug(lcQdoc).nospace() << process.program() << " timed out: " << stdErr;
+        process.kill();
+        return false;
+    }
+
+    if (process.exitStatus() != QProcess::NormalExit) {
+        qCDebug(lcQdoc).nospace() << process.program() << " crashed: " << stdErr;
+        return false;
+    }
+
+    if (process.exitCode() != 0) {
+        qCDebug(lcQdoc).nospace() <<  process.program() << " exited with "
+            << process.exitCode() << ": " << stdErr;
+        return false;
+    }
+
+    return true;
+}
+
+/*!
+    \internal
+*/
+static QByteArray frameworkSuffix() {
+    return QByteArrayLiteral(" (framework directory)");
+}
+
+/*!
+    \internal
+    Determine the compiler's internal include paths from the output of
+
+    \badcode
+    [clang++|g++] -E -x c++ - -v </dev/null
+    \endcode
+
+    Output looks like:
+
+    \badcode
+    #include <...> search starts here:
+    /usr/local/include
+    /System/Library/Frameworks (framework directory)
+    End of search list.
+    \endcode
+*/
+QStringList getInternalIncludePaths(const QString &compiler)
+{
+    QStringList result;
+    QStringList arguments;
+    arguments << QStringLiteral("-E") << QStringLiteral("-x") << QStringLiteral("c++")
+              << QStringLiteral("-") << QStringLiteral("-v");
+    QByteArray stdOut;
+    QByteArray stdErr;
+    if (!runProcess(compiler, arguments, &stdOut, &stdErr))
+        return result;
+    const QByteArrayList stdErrLines = stdErr.split('\n');
+    bool isIncludeDir = false;
+    for (const QByteArray &line : stdErrLines) {
+        if (isIncludeDir) {
+            if (line.startsWith(QByteArrayLiteral("End of search list"))) {
+                isIncludeDir = false;
+            } else {
+                QByteArray prefix("-I");
+                QByteArray headerPath{line.trimmed()};
+                if (headerPath.endsWith(frameworkSuffix())) {
+                    headerPath.truncate(headerPath.size() - frameworkSuffix().size());
+                    prefix = QByteArrayLiteral("-F");
+                }
+                result.append(QString::fromLocal8Bit(prefix + headerPath));
+            }
+        } else if (line.startsWith(QByteArrayLiteral("#include <...> search starts here"))) {
+            isIncludeDir = true;
+        }
+    }
+
+    return result;
+}
+
 } // namespace Utilities
 
 QT_END_NAMESPACE
diff --git a/src/qdoc/utilities.h b/src/qdoc/utilities.h
index f820c39bd..488c960ad 100644
--- a/src/qdoc/utilities.h
+++ b/src/qdoc/utilities.h
@@ -44,6 +44,7 @@ bool debugging();
 
 QString separator(qsizetype wordPosition, qsizetype numberOfWords);
 QString comma(qsizetype wordPosition, qsizetype numberOfWords);
+QStringList getInternalIncludePaths(const QString &compiler);
 }
 
 QT_END_NAMESPACE