Put a system-wide lock on the build directory.

So that two qbs instances can't overwrite each other's
build graphs. In practice, this is probably most relevant
for IDEs, as these hold a build graph for potentially long
periods of time.
Facilitates QLockFile that was introduced in Qt 5.1. For older
Qt versions, no locking happens.

Task-number: QBS-162
Change-Id: Ib598617fb1742eb57b6a017f40b9631d1d54e627
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

2 files changed, 7 insertions, 2 deletions

diff --git a/src/lib/corelib/language/language.cpp b/src/lib/corelib/language/language.cpp
index cc9d02180..d7815938e 100644
--- a/src/lib/corelib/language/language.cpp
+++ b/src/lib/corelib/language/language.cpp
@@ -39,6 +39,7 @@
 #include <buildgraph/transformer.h>
 #include <jsextensions/jsextensions.h>
 #include <logging/translator.h>
+#include <tools/buildgraphlocker.h>
 #include <tools/hostosinfo.h>
 #include <tools/error.h>
 #include <tools/propertyfinder.h>
@@ -937,12 +938,14 @@ void ResolvedProject::store(PersistentPool &pool) const
 }
 
 
-TopLevelProject::TopLevelProject() : locked(false), lastResolveTime(FileTime::oldestTime())
+TopLevelProject::TopLevelProject()
+    : bgLocker(0), locked(false), lastResolveTime(FileTime::oldestTime())
 {
 }
 
 TopLevelProject::~TopLevelProject()
 {
+    delete bgLocker;
 }
 
 QString TopLevelProject::deriveId(const QString &profile, const QVariantMap &config)
diff --git a/src/lib/corelib/language/language.h b/src/lib/corelib/language/language.h
index ed1b37320..e7df3232e 100644
--- a/src/lib/corelib/language/language.h
+++ b/src/lib/corelib/language/language.h
@@ -61,6 +61,7 @@ QT_END_NAMESPACE
 
 namespace qbs {
 namespace Internal {
+class BuildGraphLocker;
 class BuildGraphLoader;
 class BuildGraphVisitor;
 
@@ -460,7 +461,8 @@ public:
     QHash<QString, bool> fileExistsResults; // Results of calls to "File.exists()".
     QHash<QString, FileTime> fileLastModifiedResults; // Results of calls to "File.lastModified()".
     QScopedPointer<ProjectBuildData> buildData;
-    bool locked;
+    BuildGraphLocker *bgLocker; // This holds the system-wide build graph file lock.
+    bool locked; // This is the API-level lock for the project instance.
 
     QSet<QString> buildSystemFiles;
     FileTime lastResolveTime;