Fix QtScript on 64-bit systems with gcc 8

Similar to commit 92836d052efb6d8073136e8507083f93fb60bb80 in
qtdeclarative, we must use memcpy to do a bit-wise conversion from the
JSCell *m_ptr to an intptr_t for JSValue tag operations.

This fixes the referenced task and all the failing auto-tests.

The most visible result was that

    if ((jsvalue.immediateValue() & 0xffff000000000000ll) == 0xffff000000000000ll)
        return static_cast<int32_t>(jsvalue.immediateValue());

was "optimized" to "return 0", breaking QScriptValue::toNumber() for
integer encoded values.

[ChangeLog][QtScript] Fix incorrect script evaluations on 64-bit systems
with gcc 8.

Change-Id: I525b6b66d0e3c5163ad7e338fd0e866cdf620dad
Task-number: QTBUG-68367
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 12 insertions, 4 deletions

diff --git a/src/3rdparty/javascriptcore/JavaScriptCore/runtime/JSValue.h b/src/3rdparty/javascriptcore/JavaScriptCore/runtime/JSValue.h
index 501ab5e..7584c52 100644
--- a/src/3rdparty/javascriptcore/JavaScriptCore/runtime/JSValue.h
+++ b/src/3rdparty/javascriptcore/JavaScriptCore/runtime/JSValue.h
@@ -773,22 +773,30 @@ namespace JSC {
     // JSValue member functions.
     inline EncodedJSValue JSValue::encode(JSValue value)
     {
-        return reinterpret_cast<EncodedJSValue>(value.m_ptr);
+        EncodedJSValue r;
+        memcpy(&r, &value.m_ptr, sizeof(r));
+        return r;
     }
 
     inline JSValue JSValue::decode(EncodedJSValue ptr)
     {
-        return JSValue(reinterpret_cast<JSCell*>(ptr));
+        JSCell *cellPtr;
+        memcpy(&cellPtr, &ptr, sizeof(cellPtr));
+        return JSValue(cellPtr);
     }
 
     inline JSValue JSValue::makeImmediate(intptr_t value)
     {
-        return JSValue(reinterpret_cast<JSCell*>(value));
+        JSCell *cellPtr;
+        memcpy(&cellPtr, &value, sizeof(cellPtr));
+        return JSValue(cellPtr);
     }
 
     inline intptr_t JSValue::immediateValue()
     {
-        return reinterpret_cast<intptr_t>(m_ptr);
+        intptr_t v;
+        memcpy(&v, &m_ptr, sizeof(v));
+        return v;
     }
     
     // 0x0 can never occur naturally because it has a tag of 00, indicating a pointer value, but a payload of 0x0, which is in the (invalid) zero page.