Clang: Avoid using -isystem include paths

...as this leads to file locking issues on Windows and pointless
diagnostics we currently ignore when opening files from -isystem include
paths.

The usage of -isystem suppressed warnings from system headers and
resulted in a performance boost. Nowadays we can preserve this
performance optimization by making use of the new
CXTranslationUnit_IgnoreWarningsFromIncludedFiles. This flag helps us
also to suppress diagnostics from clang tidy checks, which reported
diagnostics even for -isystem headers.

Change-Id: I33e1f7169e2ff9f17c811565a5324b9da4740701
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

1 files changed, 1 insertions, 26 deletions

diff --git a/src/plugins/cpptools/compileroptionsbuilder.cpp b/src/plugins/cpptools/compileroptionsbuilder.cpp
index 786d874786..3c2dba239e 100644
--- a/src/plugins/cpptools/compileroptionsbuilder.cpp
+++ b/src/plugins/cpptools/compileroptionsbuilder.cpp
@@ -129,28 +129,10 @@ void CompilerOptionsBuilder::enableExceptions()
     add(QLatin1String("-fexceptions"));
 }
 
-static Utils::FileName absoluteDirectory(const QString &filePath)
-{
-    return Utils::FileName::fromString(QFileInfo(filePath + '/').absolutePath());
-}
-
-static Utils::FileName projectTopLevelDirectory(const ProjectPart &projectPart)
-{
-    if (!projectPart.project)
-        return Utils::FileName();
-    const Utils::FileName result = projectPart.project->projectDirectory();
-    const Utils::FileName vcsTopLevel = Utils::FileName::fromString(
-                Core::VcsManager::findTopLevelForDirectory(result.toString()));
-    if (result.isChildOf(vcsTopLevel))
-        return vcsTopLevel;
-    return result;
-}
-
 void CompilerOptionsBuilder::addHeaderPathOptions()
 {
     typedef ProjectPartHeaderPath HeaderPath;
     const QString defaultPrefix = includeDirOption();
-    const Utils::FileName projectDirectory = projectTopLevelDirectory(m_projectPart);
 
     QStringList result;
 
@@ -170,14 +152,7 @@ void CompilerOptionsBuilder::addHeaderPathOptions()
         default: // This shouldn't happen, but let's be nice..:
             // intentional fall-through:
         case HeaderPath::IncludePath:
-            path = absoluteDirectory(headerPath.path);
-            if (projectDirectory.isEmpty()
-                    || path == projectDirectory
-                    || path.isChildOf(projectDirectory)) {
-                prefix = defaultPrefix;
-            } else {
-                prefix = SYSTEM_INCLUDE_PREFIX;
-            }
+            prefix = defaultPrefix;
             break;
         }