Clang: Disable internal threads in libclang

We already run all operations in threads to avoid blocking, there is no
need to start more threads within libclang. Before this change, a
reparse would trigger 3 threads to start:
  1. clangbackend: Utils::runAsync() for the job
  2. libclang-internal: thread for reparse
  3. libclang-internal: thread for annotating tokens (highlighting)

Ensure that we use the same stack size for our threads as libclang was
doing internally. C++ parsers usually have higher stack size
requirements.

Change-Id: I2f67602ddfbf77ea2c69144b56acf64ba08041f6
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libs/clangsupport/clangcodemodelconnectionclient.cpp b/src/libs/clangsupport/clangcodemodelconnectionclient.cpp
index 1938d06353..33d8987024 100644
--- a/src/libs/clangsupport/clangcodemodelconnectionclient.cpp
+++ b/src/libs/clangsupport/clangcodemodelconnectionclient.cpp
@@ -25,6 +25,7 @@
 
 #include "clangcodemodelconnectionclient.h"
 
+#include <utils/environment.h>
 #include <utils/temporarydirectory.h>
 
 #include <QCoreApplication>
@@ -50,6 +51,10 @@ ClangCodeModelConnectionClient::ClangCodeModelConnectionClient(
     m_processCreator.setTemporaryDirectoryPattern("clangbackend-XXXXXX");
     m_processCreator.setArguments({connectionName()});
 
+    Utils::Environment environment;
+    environment.set(QStringLiteral("LIBCLANG_NOTHREADS"), QString());
+    m_processCreator.setEnvironment(environment);
+
     stdErrPrefixer().setPrefix("clangbackend.stderr: ");
     stdOutPrefixer().setPrefix("clangbackend.stdout: ");
 }