Add Q_ALLOCA_VAR, Q_ALLOCA_DECLARE and Q_ALLOCA_ASSIGN macros

Define Q_ALLOCA_VAR macro to be used instead of #ifdeffing
the occurrences of alloca() in case it's not supported.
Q_ALLOCA_DECLARE and Q_ALLOCA_ASSIGN macros separate
memory allocation from the declaration and RAII.

Change-Id: Idc7551642c48a968a44bcade14d84800a3a1270e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

9 files changed, 54 insertions, 10 deletions

diff --git a/src/qml/compiler/qv4compiler.cpp b/src/qml/compiler/qv4compiler.cpp
index cd822a2614..9cfac4a676 100644
--- a/src/qml/compiler/qv4compiler.cpp
+++ b/src/qml/compiler/qv4compiler.cpp
@@ -220,7 +220,7 @@ QV4::CompiledData::Unit *QV4::Compiler::JSUnitGenerator::generateUnit(GeneratorO
             registerString(*f->locals.at(i));
     }
 
-    CompiledData::LEUInt32 *functionOffsets = reinterpret_cast<CompiledData::LEUInt32*>(alloca(irModule->functions.size() * sizeof(CompiledData::LEUInt32)));
+    Q_ALLOCA_VAR(CompiledData::LEUInt32, functionOffsets, irModule->functions.size() * sizeof(CompiledData::LEUInt32));
     uint jsClassDataOffset = 0;
 
     char *dataPtr;
diff --git a/src/qml/jit/qv4regalloc.cpp b/src/qml/jit/qv4regalloc.cpp
index d5da863ee0..e5abaa7458 100644
--- a/src/qml/jit/qv4regalloc.cpp
+++ b/src/qml/jit/qv4regalloc.cpp
@@ -1575,7 +1575,7 @@ static void longestAvailableReg(int *nextUses, int nextUseCount, int &reg, int &
 
 #define CALLOC_ON_STACK(ty, ptr, sz, val) \
     Q_ASSERT(sz > 0); \
-    ty *ptr = reinterpret_cast<ty *>(alloca(sizeof(ty) * (sz))); \
+    Q_ALLOCA_VAR(ty, ptr, sizeof(ty) * (sz)); \
     for (ty *it = ptr, *eit = ptr + (sz); it != eit; ++it) \
         *it = val;
 
diff --git a/src/qml/jsruntime/qv4regexpobject.cpp b/src/qml/jsruntime/qv4regexpobject.cpp
index 40682aaa4b..0894d0c25b 100644
--- a/src/qml/jsruntime/qv4regexpobject.cpp
+++ b/src/qml/jsruntime/qv4regexpobject.cpp
@@ -367,7 +367,7 @@ void RegExpPrototype::method_exec(const BuiltinFunction *, Scope &scope, CallDat
         RETURN_RESULT(Encode::null());
     }
 
-    uint* matchOffsets = (uint*)alloca(r->value()->captureCount() * 2 * sizeof(uint));
+    Q_ALLOCA_VAR(uint, matchOffsets, r->value()->captureCount() * 2 * sizeof(uint));
     const int result = Scoped<RegExp>(scope, r->value())->match(s, offset, matchOffsets);
 
     Scoped<RegExpCtor> regExpCtor(scope, scope.engine->regExpCtor());
diff --git a/src/qml/jsruntime/qv4stringobject.cpp b/src/qml/jsruntime/qv4stringobject.cpp
index 3c6a24e035..1596f4b0fa 100644
--- a/src/qml/jsruntime/qv4stringobject.cpp
+++ b/src/qml/jsruntime/qv4stringobject.cpp
@@ -634,7 +634,7 @@ void StringPrototype::method_search(const BuiltinFunction *, Scope &scope, CallD
         Q_ASSERT(regExp);
     }
     Scoped<RegExp> re(scope, regExp->value());
-    uint* matchOffsets = (uint*)alloca(regExp->value()->captureCount() * 2 * sizeof(uint));
+    Q_ALLOCA_VAR(uint, matchOffsets, regExp->value()->captureCount() * 2 * sizeof(uint));
     uint result = re->match(string, /*offset*/0, matchOffsets);
     if (result == JSC::Yarr::offsetNoMatch)
         scope.result = Encode(-1);
@@ -705,7 +705,7 @@ void StringPrototype::method_split(const BuiltinFunction *, Scope &scope, CallDa
     ScopedString s(scope);
     if (re) {
         uint offset = 0;
-        uint* matchOffsets = (uint*)alloca(re->value()->captureCount() * 2 * sizeof(uint));
+        Q_ALLOCA_VAR(uint, matchOffsets, re->value()->captureCount() * 2 * sizeof(uint));
         while (true) {
             Scoped<RegExp> regexp(scope, re->value());
             uint result = regexp->match(text, offset, matchOffsets);
diff --git a/src/qml/jsruntime/qv4vme_moth.cpp b/src/qml/jsruntime/qv4vme_moth.cpp
index b9183313cd..be2772c23f 100644
--- a/src/qml/jsruntime/qv4vme_moth.cpp
+++ b/src/qml/jsruntime/qv4vme_moth.cpp
@@ -402,7 +402,7 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
         }
     }
 
-    QV4::Value **scopes = static_cast<QV4::Value **>(alloca(sizeof(QV4::Value *)*(2 + 2*scopeDepth)));
+    Q_ALLOCA_VAR(QV4::Value*, scopes, sizeof(QV4::Value *)*(2 + 2*scopeDepth));
     {
         scopes[0] = const_cast<QV4::Value *>(context->d()->compilationUnit->constants);
         // stack gets setup in push instruction
@@ -957,8 +957,6 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
             return QV4::Encode::undefined();
         code = exceptionHandler;
     }
-
-
 }
 
 #ifdef MOTH_THREADED_INTERPRETER
diff --git a/src/qml/qml/qqmlvaluetypewrapper.cpp b/src/qml/qml/qqmlvaluetypewrapper.cpp
index 44b612e7d2..41bb85c351 100644
--- a/src/qml/qml/qqmlvaluetypewrapper.cpp
+++ b/src/qml/qml/qqmlvaluetypewrapper.cpp
@@ -290,9 +290,11 @@ int QQmlValueTypeWrapper::typeId() const
 bool QQmlValueTypeWrapper::write(QObject *target, int propertyIndex) const
 {
     bool destructGadgetOnExit = false;
+    Q_ALLOCA_DECLARE(void, gadget);
     if (const QQmlValueTypeReference *ref = as<const QQmlValueTypeReference>()) {
         if (!d()->gadgetPtr) {
-            d()->gadgetPtr = alloca(d()->valueType->metaType.sizeOf());
+            Q_ALLOCA_ASSIGN(void, gadget, d()->valueType->metaType.sizeOf());
+            d()->gadgetPtr = gadget;
             d()->valueType->metaType.construct(d()->gadgetPtr, 0);
             destructGadgetOnExit = true;
         }
diff --git a/src/qml/qtqmlglobal_p.h b/src/qml/qtqmlglobal_p.h
index 63585fd62e..026be5a703 100644
--- a/src/qml/qtqmlglobal_p.h
+++ b/src/qml/qtqmlglobal_p.h
@@ -55,6 +55,46 @@
 #include <QtQml/private/qtqml-config_p.h>
 #include <QtQml/qtqmlglobal.h>
 
+// Define Q_ALLOCA_VAR macro to be used instead of #ifdeffing
+// the occurrences of alloca() in case it's not supported.
+// Q_ALLOCA_DECLARE and Q_ALLOCA_ASSIGN macros separate
+// memory allocation from the declaration and RAII.
+#define Q_ALLOCA_VAR(type, name, size) \
+    Q_ALLOCA_DECLARE(type, name); \
+    Q_ALLOCA_ASSIGN(type, name, size)
+
+#if QT_CONFIG(alloca)
+
+#define Q_ALLOCA_DECLARE(type, name) \
+    type *name = 0
+
+#define Q_ALLOCA_ASSIGN(type, name, size) \
+    name = static_cast<type*>(alloca(size))
+
+#else
+QT_BEGIN_NAMESPACE
+class Qt_AllocaWrapper
+{
+public:
+    Qt_AllocaWrapper() { m_data = 0; }
+    ~Qt_AllocaWrapper() { free(m_data); }
+    void *data() { return m_data; }
+    void allocate(int size) { m_data = malloc(size); }
+private:
+    void *m_data;
+};
+QT_END_NAMESPACE
+
+#define Q_ALLOCA_DECLARE(type, name) \
+    Qt_AllocaWrapper _qt_alloca_##name; \
+    type *name = 0
+
+#define Q_ALLOCA_ASSIGN(type, name, size) \
+    _qt_alloca_##name.allocate(size); \
+    name = static_cast<type*>(_qt_alloca_##name.data())
+
+#endif
+
 #if defined(QT_BUILD_QMLDEVTOOLS_LIB) || defined(QT_QMLDEVTOOLS_LIB)
 #    define Q_QML_PRIVATE_EXPORT
 #else
diff --git a/src/qml/types/qqmllistmodel.cpp b/src/qml/types/qqmllistmodel.cpp
index cc4ccbaeb1..5e2ff9b15b 100644
--- a/src/qml/types/qqmllistmodel.cpp
+++ b/src/qml/types/qqmllistmodel.cpp
@@ -1268,7 +1268,7 @@ void ModelNodeMetaObject::updateValues()
     const int roleCount = m_model->m_listModel->roleCount();
     if (!m_initialized) {
         if (roleCount) {
-            int *changedRoles = reinterpret_cast<int *>(alloca(roleCount * sizeof(int)));
+            Q_ALLOCA_VAR(int, changedRoles, roleCount * sizeof(int));
             for (int i = 0; i < roleCount; ++i)
                 changedRoles[i] = i;
             emitDirectNotifies(changedRoles, roleCount);
diff --git a/src/qmldevtools/qtqmldevtoolsglobal_p.h b/src/qmldevtools/qtqmldevtoolsglobal_p.h
index e1a01aa78d..5cb8a9275a 100644
--- a/src/qmldevtools/qtqmldevtoolsglobal_p.h
+++ b/src/qmldevtools/qtqmldevtoolsglobal_p.h
@@ -53,6 +53,10 @@
 
 #include <QtCore/qglobal.h>
 
+// All host systems are assumed to have alloca().
+#define Q_ALLOCA_VAR(type, name, size) \
+    type *name = static_cast<type*>(alloca(size))
+
 QT_BEGIN_NAMESPACE
 
 #define Q_QML_EXPORT