shiboken: Search for Clang builtin-includes at runtime

Replace the search executed at build time by CMake by
a run time search in shiboken since the location at build time
typically won't match any more for the deployment case.

Task-number: PYSIDE-693
Change-Id: Ib15fbba5d8c3fecf30aaae7195b88a648a7ed0fe
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

3 files changed, 82 insertions, 56 deletions

diff --git a/sources/shiboken2/ApiExtractor/CMakeLists.txt b/sources/shiboken2/ApiExtractor/CMakeLists.txt
index a3301a068..b67a352f0 100644
--- a/sources/shiboken2/ApiExtractor/CMakeLists.txt
+++ b/sources/shiboken2/ApiExtractor/CMakeLists.txt
@@ -31,13 +31,6 @@ add_definitions(-DQT_PLUGIN)
 add_definitions(-DQT_SHARED)
 add_definitions(-DRXX_ALLOCATOR_INIT_0)
 
-# Pass the path to the clang includes dir, so it headers like stdarg.h.
-if(UNIX AND NOT APPLE)
-    add_definitions(-DCLANG_BUILTIN_INCLUDES_DIR="${CLANG_BUILTIN_INCLUDES_DIR}")
-else()
-    add_definitions(-DCLANG_BUILTIN_INCLUDES_DIR="")
-endif()
-
 set(apiextractor_SRC
 apiextractor.cpp
 abstractmetabuilder.cpp
diff --git a/sources/shiboken2/ApiExtractor/clangparser/compilersupport.cpp b/sources/shiboken2/ApiExtractor/clangparser/compilersupport.cpp
index e7de8fdb3..9f4f7dc03 100644
--- a/sources/shiboken2/ApiExtractor/clangparser/compilersupport.cpp
+++ b/sources/shiboken2/ApiExtractor/clangparser/compilersupport.cpp
@@ -29,8 +29,14 @@
 #include "compilersupport.h"
 #include "header_paths.h"
 
+#include <reporthandler.h>
+
 #include <QtCore/QDebug>
+#include <QtCore/QDir>
+#include <QtCore/QFile>
+#include <QtCore/QFileInfo>
 #include <QtCore/QProcess>
+#include <QtCore/QStandardPaths>
 #include <QtCore/QStringList>
 #include <QtCore/QVersionNumber>
 
@@ -155,6 +161,68 @@ static inline bool isRedHat74()
 static QByteArray noStandardIncludeOption() { return QByteArrayLiteral("-nostdinc"); }
 #endif
 
+// The clang builtin includes directory is used to find the definitions for
+// intrinsic functions and builtin types. It is necessary to use the clang
+// includes to prevent redefinition errors. The default toolchain includes
+// should be picked up automatically by clang without specifying
+// them implicitly.
+
+#if defined(Q_OS_UNIX) && !defined(Q_OS_DARWIN)
+#  define NEED_CLANG_BUILTIN_INCLUDES 1
+#else
+#  define NEED_CLANG_BUILTIN_INCLUDES 0
+#endif
+
+#if NEED_CLANG_BUILTIN_INCLUDES
+static QString findClang()
+{
+    for (const char *envVar : {"LLVM_INSTALL_DIR", "CLANG_INSTALL_DIR"}) {
+        if (qEnvironmentVariableIsSet(envVar)) {
+            const QString path = QFile::decodeName(qgetenv(envVar));
+            if (QFileInfo::exists(path))
+                return path;
+        }
+    }
+    const QString llvmConfig =
+        QStandardPaths::findExecutable(QLatin1String("llvm-config"));
+    if (!llvmConfig.isEmpty()) {
+        QByteArray stdOut;
+        if (runProcess(llvmConfig, QStringList{QLatin1String("--prefix")}, &stdOut)) {
+            const QString path = QFile::decodeName(stdOut.trimmed());
+            if (QFileInfo::exists(path))
+                return path;
+        }
+    }
+    return QString();
+}
+
+static QString findClangBuiltInIncludesDir()
+{
+    // Find the include directory of the highest version.
+    const QString clangPath = findClang();
+    if (!clangPath.isEmpty()) {
+        QString candidate;
+        QVersionNumber lastVersionNumber(1, 0, 0);
+        QDir clangDir(clangPath + QLatin1String("/lib/clang"));
+        const QFileInfoList versionDirs =
+            clangDir.entryInfoList(QDir::Dirs | QDir::NoDotAndDotDot);
+        for (const QFileInfo &fi : versionDirs) {
+            const QString fileName = fi.fileName();
+            if (fileName.at(0).isDigit()) {
+                const QVersionNumber versionNumber = QVersionNumber::fromString(fileName.at(0));
+                if (!versionNumber.isNull() && versionNumber > lastVersionNumber) {
+                    candidate = fi.absoluteFilePath();
+                    lastVersionNumber = versionNumber;
+                }
+            }
+        }
+        if (!candidate.isEmpty())
+            return candidate + QStringLiteral("/include");
+    }
+    return QString();
+}
+#endif // NEED_CLANG_BUILTIN_INCLUDES
+
 // Returns clang options needed for emulating the host compiler
 QByteArrayList emulatedCompilerOptions()
 {
@@ -169,16 +237,21 @@ QByteArrayList emulatedCompilerOptions()
 #elif defined(Q_CC_GNU)
     HeaderPaths headerPaths;
 
-    // The clang builtin includes directory is used to find the definitions for intrinsic functions
-    // and builtin types. It is necessary to use the clang includes to prevent redefinition errors.
-    // The default toolchain includes should be picked up automatically by clang without specifying
-    // them implicitly.
-    QByteArray clangBuiltinIncludesDir(CLANG_BUILTIN_INCLUDES_DIR);
-
-    if (!clangBuiltinIncludesDir.isEmpty()) {
-        result.append(QByteArrayLiteral("-isystem"));
-        result.append(clangBuiltinIncludesDir);
+#if NEED_CLANG_BUILTIN_INCLUDES
+    const QString clangBuiltinIncludesDir =
+        QDir::toNativeSeparators(findClangBuiltInIncludesDir());
+    if (clangBuiltinIncludesDir.isEmpty()) {
+        qCWarning(lcShiboken, "Unable to locate Clang's built-in include directory "
+                  "(neither by checking the environment variables LLVM_INSTALL_DIR, CLANG_INSTALL_DIR "
+                  " nor running llvm-config). This may lead to parse errors.");
+    } else {
+        qCInfo(lcShiboken, "CLANG builtins includes directory: %s",
+               qPrintable(clangBuiltinIncludesDir));
+        headerPaths.append(HeaderPath{QFile::encodeName(clangBuiltinIncludesDir),
+                                      HeaderType::System});
     }
+#endif // NEED_CLANG_BUILTIN_INCLUDES
+
     // Append the c++ include paths since Clang is unable to find <list> etc
     // on RHEL 7.4 with g++ 6.3. A fix for this has been added to Clang 5.0,
     // so, the code can be removed once Clang 5.0 is the minimum version.
diff --git a/sources/shiboken2/CMakeLists.txt b/sources/shiboken2/CMakeLists.txt
index 852e14c1a..1af84fca1 100644
--- a/sources/shiboken2/CMakeLists.txt
+++ b/sources/shiboken2/CMakeLists.txt
@@ -113,46 +113,6 @@ endif()
 
 message(STATUS "CLANG: ${CLANG_DIR}, ${CLANG_LIBRARY} detected by ${CLANG_DIR_SOURCE}")
 
-# Find highest version clang builtin includes folder to pass along to shiboken.
-set(CLANG_BUILTIN_INCLUDES_DIR_PREFIX ${CLANG_DIR}/lib/clang)
-file(GLOB CLANG_BUILTIN_INCLUDES_DIR_CANDIDATES "${CLANG_BUILTIN_INCLUDES_DIR_PREFIX}/*")
-
-# Collect only directories, and not files, and only directories starting with a number.
-set(CLANG_BUILTIN_INCLUDES_DIR_VERSIONS "")
-foreach(candidate ${CLANG_BUILTIN_INCLUDES_DIR_CANDIDATES})
-    get_filename_component(candidate_basename ${candidate} NAME)
-    if (IS_DIRECTORY ${candidate} AND ${candidate_basename} MATCHES "^[0-9]") # starts with number
-        list(APPEND CLANG_BUILTIN_INCLUDES_DIR_VERSIONS ${candidate})
-    endif()
-endforeach()
-
-# Sort in alphabetical order the list of version folders.
-list(SORT CLANG_BUILTIN_INCLUDES_DIR_VERSIONS)
-
-# Reverse it so the first element is the highest version.
-list(REVERSE CLANG_BUILTIN_INCLUDES_DIR_VERSIONS)
-
-message(STATUS
-    "Found the following CLANG builtins includes directories: ${CLANG_BUILTIN_INCLUDES_DIR_VERSIONS} \
-     Considered the following directories: ${CLANG_BUILTIN_INCLUDES_DIR_CANDIDATES}")
-if(CLANG_BUILTIN_INCLUDES_DIR_VERSIONS)
-    # Get highest version.
-    list(GET CLANG_BUILTIN_INCLUDES_DIR_VERSIONS 0 CLANG_BUILTIN_INCLUDES_DIR_HIGHEST_VERSION)
-    if (CLANG_BUILTIN_INCLUDES_DIR_HIGHEST_VERSION)
-        # Set the final variable to the full include path to pass along to shiboken.
-        set(CLANG_BUILTIN_INCLUDES_DIR "${CLANG_BUILTIN_INCLUDES_DIR_HIGHEST_VERSION}/include")
-    endif()
-endif()
-
-message(STATUS "CLANG builtins includes directory chosen: ${CLANG_BUILTIN_INCLUDES_DIR}")
-
-# We don't exit with a hard error here, because it is uncertain whether all clang extra include
-# paths follow the same layout across OSes and distros.
-if (NOT CLANG_BUILTIN_INCLUDES_DIR)
-    message(WARNING "No CLANG builtins includes directory found. This may lead to shiboken \
-                     execution failure.")
-endif()
-
 set(CLANG_EXTRA_INCLUDES ${CLANG_DIR}/include)
 set(CLANG_EXTRA_LIBRARIES ${CLANG_LIBRARY})