Implement the dead temporal zone

With const and let it is possible to access the declared member before
initialization. This is expected to throw a type reference error at
run-time.

We initialize such variables with the empty value when entering their
scope and check upon access for that. For locals we place the lexically
scoped variables at the end. For register allocated lexical variables we
group them into one batch and remember the index/size.

Change-Id: Icb493ee0de0525bb682e1bc58981a4dfd33f750e
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 8 insertions, 3 deletions

diff --git a/src/qml/compiler/qv4compileddata_p.h b/src/qml/compiler/qv4compileddata_p.h
index dca38eae54..1f6c591ada 100644
--- a/src/qml/compiler/qv4compileddata_p.h
+++ b/src/qml/compiler/qv4compileddata_p.h
@@ -237,6 +237,8 @@ struct Block
 {
     quint32_le nLocals;
     quint32_le localsOffset;
+    quint16_le sizeOfLocalTemporalDeadZone;
+    quint16_le padding;
 
     const quint32_le *localsTable() const { return reinterpret_cast<const quint32_le *>(reinterpret_cast<const char *>(this) + localsOffset); }
 
@@ -251,7 +253,7 @@ struct Block
         return (a + 7) & ~size_t(7);
     }
 };
-static_assert(sizeof(Block) == 8, "Block structure needs to have the expected size to be binary compatible on disk when generated by host compiler and loaded by target");
+static_assert(sizeof(Block) == 12, "Block structure needs to have the expected size to be binary compatible on disk when generated by host compiler and loaded by target");
 
 // Function is aligned on an 8-byte boundary to make sure there are no bus errors or penalties
 // for unaligned access. The ordering of the fields is also from largest to smallest.
@@ -276,6 +278,10 @@ struct Function
     quint16_le nLineNumbers;
     size_t lineNumberOffset() const { return localsOffset + nLocals * sizeof(quint32); }
     quint32_le nestedFunctionIndex; // for functions that only return a single closure, used in signal handlers
+    quint16_le sizeOfLocalTemporalDeadZone;
+    quint16_le firstTemporalDeadZoneRegister;
+    quint16_le sizeOfRegisterTemporalDeadZone;
+    quint16_le nRegisters;
     Location location;
 
     // Qml Extensions Begin
@@ -293,7 +299,6 @@ struct Function
     // Keep all unaligned data at the end
     quint8 flags;
     quint8 padding1;
-    quint16_le nRegisters;
 
     //    quint32 formalsIndex[nFormals]
     //    quint32 localsIndex[nLocals]
@@ -326,7 +331,7 @@ struct Function
         return (a + 7) & ~size_t(7);
     }
 };
-static_assert(sizeof(Function) == 48, "Function structure needs to have the expected size to be binary compatible on disk when generated by host compiler and loaded by target");
+static_assert(sizeof(Function) == 52, "Function structure needs to have the expected size to be binary compatible on disk when generated by host compiler and loaded by target");
 
 struct Method {
     enum Type {