Bug 1357075 - Pad a nop to unwind to the scope just before a destructuring iterator close trynote

Issue #74

7 files changed, 43 insertions, 5 deletions

diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index b2e48d7ea..4d3b60c2f 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -5318,6 +5318,14 @@ BytecodeEmitter::wrapWithDestructuringIteratorCloseTryNote(int32_t iterDepth, In
 {
     MOZ_ASSERT(this->stackDepth >= iterDepth);
 
+    // Pad a nop at the beginning of the bytecode covered by the trynote so
+    // that when unwinding environments, we may unwind to the scope
+    // corresponding to the pc *before* the start, in case the first bytecode
+    // emitted by |emitter| is the start of an inner scope. See comment above
+    // UnwindEnvironmentToTryPc.
+    if (!emit1(JSOP_TRY_DESTRUCTURING_ITERCLOSE))
+        return false;
+
     ptrdiff_t start = offset();
     if (!emitter(this))
         return false;
diff --git a/js/src/jit-test/tests/parser/bug-1357075.js b/js/src/jit-test/tests/parser/bug-1357075.js
new file mode 100644
index 000000000..47482e372
--- /dev/null
+++ b/js/src/jit-test/tests/parser/bug-1357075.js
@@ -0,0 +1,10 @@
+// |jit-test| error: TypeError
+
+var iterable = {};
+var iterator = {
+  return: 1
+};
+iterable[Symbol.iterator] = function() {
+  return iterator;
+};
+for ([ class get {} ().iterator ] of [iterable]) {}
diff --git a/js/src/jit/BaselineCompiler.cpp b/js/src/jit/BaselineCompiler.cpp
index 07d8e629d..3fa5a80ed 100644
--- a/js/src/jit/BaselineCompiler.cpp
+++ b/js/src/jit/BaselineCompiler.cpp
@@ -1063,6 +1063,12 @@ BaselineCompiler::emit_JSOP_NOP_DESTRUCTURING()
 }
 
 bool
+BaselineCompiler::emit_JSOP_TRY_DESTRUCTURING_ITERCLOSE()
+{
+    return true;
+}
+
+bool
 BaselineCompiler::emit_JSOP_LABEL()
 {
     return true;
diff --git a/js/src/jit/BaselineCompiler.h b/js/src/jit/BaselineCompiler.h
index 0bacf6f18..6b5bf009e 100644
--- a/js/src/jit/BaselineCompiler.h
+++ b/js/src/jit/BaselineCompiler.h
@@ -226,7 +226,7 @@ namespace jit {
     _(JSOP_SPREADSUPERCALL)    \
     _(JSOP_THROWSETCONST)      \
     _(JSOP_THROWSETALIASEDCONST) \
-    _(JSOP_THROWSETCALLEE) \
+    _(JSOP_THROWSETCALLEE)     \
     _(JSOP_INITHIDDENPROP_GETTER) \
     _(JSOP_INITHIDDENPROP_SETTER) \
     _(JSOP_INITHIDDENELEM)     \
@@ -234,8 +234,9 @@ namespace jit {
     _(JSOP_INITHIDDENELEM_SETTER) \
     _(JSOP_CHECKOBJCOERCIBLE)  \
     _(JSOP_DEBUGCHECKSELFHOSTED) \
-    _(JSOP_JUMPTARGET) \
-    _(JSOP_IS_CONSTRUCTING)
+    _(JSOP_JUMPTARGET)         \
+    _(JSOP_IS_CONSTRUCTING)    \
+    _(JSOP_TRY_DESTRUCTURING_ITERCLOSE)
 
 class BaselineCompiler : public BaselineCompilerSpecific
 {
diff --git a/js/src/jit/IonBuilder.cpp b/js/src/jit/IonBuilder.cpp
index ed09fb504..54d05cac4 100644
--- a/js/src/jit/IonBuilder.cpp
+++ b/js/src/jit/IonBuilder.cpp
@@ -1678,6 +1678,7 @@ IonBuilder::inspectOpcode(JSOp op)
     switch (op) {
       case JSOP_NOP:
       case JSOP_NOP_DESTRUCTURING:
+      case JSOP_TRY_DESTRUCTURING_ITERCLOSE:
       case JSOP_LINENO:
       case JSOP_LOOPENTRY:
       case JSOP_JUMPTARGET:
diff --git a/js/src/vm/Interpreter.cpp b/js/src/vm/Interpreter.cpp
index d20e5284d..b747e4d7a 100644
--- a/js/src/vm/Interpreter.cpp
+++ b/js/src/vm/Interpreter.cpp
@@ -1080,6 +1080,9 @@ js::UnwindEnvironmentToTryPc(JSScript* script, JSTryNote* tn)
     if (tn->kind == JSTRY_CATCH || tn->kind == JSTRY_FINALLY) {
         pc -= JSOP_TRY_LENGTH;
         MOZ_ASSERT(*pc == JSOP_TRY);
+    } else if (tn->kind == JSTRY_DESTRUCTURING_ITERCLOSE) {
+        pc -= JSOP_TRY_DESTRUCTURING_ITERCLOSE_LENGTH;
+        MOZ_ASSERT(*pc == JSOP_TRY_DESTRUCTURING_ITERCLOSE);
     }
     return pc;
 }
@@ -1917,7 +1920,7 @@ CASE(JSOP_UNUSED192)
 CASE(JSOP_UNUSED209)
 CASE(JSOP_UNUSED210)
 CASE(JSOP_UNUSED211)
-CASE(JSOP_UNUSED220)
+CASE(JSOP_TRY_DESTRUCTURING_ITERCLOSE)
 CASE(JSOP_UNUSED221)
 CASE(JSOP_UNUSED222)
 CASE(JSOP_UNUSED223)
diff --git a/js/src/vm/Opcodes.h b/js/src/vm/Opcodes.h
index 3848445ff..4b044c8d8 100644
--- a/js/src/vm/Opcodes.h
+++ b/js/src/vm/Opcodes.h
@@ -2211,7 +2211,16 @@
      *   Stack: result => result, callable
      */ \
     macro(JSOP_CHECKISCALLABLE, 219, "checkiscallable", NULL, 2, 1, 1, JOF_UINT8) \
-    macro(JSOP_UNUSED220,     220,"unused220",     NULL,  1,  0,  0,  JOF_BYTE) \
+    \
+    /*
+     * No-op used by the exception unwinder to determine the correct
+     * environment to unwind to when performing IteratorClose due to
+     * destructuring.
+     *   Category: Other
+     *   Operands:
+     *   Stack: =>
+     */ \
+    macro(JSOP_TRY_DESTRUCTURING_ITERCLOSE, 220, "try-destructuring-iterclose", NULL, 1, 0, 0, JOF_BYTE) \
     macro(JSOP_UNUSED221,     221,"unused221",     NULL,  1,  0,  0,  JOF_BYTE) \
     macro(JSOP_UNUSED222,     222,"unused222",     NULL,  1,  0,  0,  JOF_BYTE) \
     macro(JSOP_UNUSED223,     223,"unused223",     NULL,  1,  0,  0,  JOF_BYTE) \