compiler: fix incorrect loop break targets

When patching jump targets for break statments while compiling for-loop
statments, we need jump beyond the instructions popping intermediate loop
variables off the stack but before the pop instructions removing local
loop body variables to prevent a stack position mismatch between compiler
and vm.

Before that change, local loop body variables remained on the stack,
breaking the expected stack layout.

Fixes: b3d758b compiler: ("fix for/break miscompilation")
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 12 insertions, 8 deletions

diff --git a/compiler.c b/compiler.c
index 3582386..f69ee2d 100644
--- a/compiler.c
+++ b/compiler.c
@@ -2242,10 +2242,10 @@ uc_compiler_compile_for_in(uc_compiler_t *compiler, bool local, uc_token_t *kvar
 	if (vvar)
 		uc_compiler_emit_insn(compiler, 0, I_POP);
 
-	uc_compiler_leave_scope(compiler);
-
 	/* patch up break/continue */
 	uc_compiler_backpatch(compiler, chunk->count, skip_jmp + 5);
+
+	uc_compiler_leave_scope(compiler);
 }
 
 static void
@@ -2355,10 +2355,10 @@ uc_compiler_compile_for_count(uc_compiler_t *compiler, bool local, uc_token_t *v
 	if (test_off)
 		uc_compiler_set_jmpaddr(compiler, test_off, chunk->count);
 
-	uc_compiler_leave_scope(compiler);
-
 	/* patch up break/continue */
 	uc_compiler_backpatch(compiler, chunk->count, incr_off);
+
+	uc_compiler_leave_scope(compiler);
 }
 
 static void
diff --git a/tests/custom/04_bugs/10_break_stack_mismatch b/tests/custom/04_bugs/10_break_stack_mismatch
index ae16dac..c9c82c5 100644
--- a/tests/custom/04_bugs/10_break_stack_mismatch
+++ b/tests/custom/04_bugs/10_break_stack_mismatch
@@ -13,12 +13,14 @@ values or segmentation faults at runtime.
 	for (let y in [2])
 		break;
 
-	print(x, "\n");
+	let z = 3;
+
+	print([ x, z ], "\n");
 %}
 -- End --
 
 -- Expect stdout --
-1
+[ 1, 3 ]
 -- End --
 
 
@@ -29,10 +31,12 @@ values or segmentation faults at runtime.
 	for (let y = 0; y < 1; y++)
 		break;
 
-	print(x, "\n");
+	let z = 3;
+
+	print([ x, z ], "\n");
 %}
 -- End --
 
 -- Expect stdout --
-1
+[ 1, 3 ]
 -- End --