Fix: leb128: sign bit must be extended

Author: kubo39

source/binary/leb128.d

@@ -0,0 +1,27 @@
+module binary.leb128;
+
+private import std.bitmanip : read;
+
+package T leb128(T)(ref const(ubyte)[] input)
+    if (is(T == int) || is(T == uint))
+{
+    T val = 0;
+    uint shift = 0;
+    enum size = 8 << 3;
+    ubyte b;
+
+    while (true)
+    {
+        b = input.read!ubyte();
+        val |= (b & 0x7F) << shift;
+        shift += 7;
+        if ((b & 0x80) == 0) break;
+    }
+    static if (is(T == int))
+    {
+        // sign bit must be extended.
+        if (shift < size && (b & 0x40) != 0)
+            val |= -(1 << shift);
+    }
+    return val;
+}

source/binary/mod.d

@@ -1,6 +1,7 @@
 module binary.mod;
 
 import binary.instruction;
+import binary.leb128;
 import binary.opcode;
 import binary.section;
 import binary.types;
@@ -103,21 +104,6 @@ Module decodeModule(ref const(ubyte)[] input)
 
 private:
 
-uint leb128(T)(ref const(ubyte)[] input)
-    if (is(T == int) || is(T == uint))
-{
-    T val = 0;
-    uint shift = 0;
-    while (true)
-    {
-        const b = input.read!ubyte();
-        val |= (b & 0x7F) << shift;
-        if ((b & 0x80) == 0) break;
-        shift += 7;
-    }
-    return val;
-}
-
 ///
 Tuple!(SectionCode, uint) decodeSectionHeader(ref const(ubyte)[] input)
 {