From 1a82d296e752ada05947a5184a89196bd8dc1100 Mon Sep 17 00:00:00 2001
From: pca006132 <jl@m-labs.hk>
Date: Sat, 26 Mar 2022 20:58:37 +0800
Subject: [PATCH] nac3core/codegen: prevent users from modifying loop counter

Fixes #211
---
 nac3core/src/codegen/stmt.rs    | 4 +++-
 nac3standalone/demo/src/loop.py | 9 +++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 nac3standalone/demo/src/loop.py

diff --git a/nac3core/src/codegen/stmt.rs b/nac3core/src/codegen/stmt.rs
index 5c3478065..fa869d309 100644
--- a/nac3core/src/codegen/stmt.rs
+++ b/nac3core/src/codegen/stmt.rs
@@ -189,7 +189,8 @@ pub fn gen_for<'ctx, 'a, G: CodeGenerator>(
         if ctx.unifier.unioned(iter.custom.unwrap(), ctx.primitives.range) {
             // setup
             let iter_val = iter_val.into_pointer_value();
-            let i = generator.gen_store_target(ctx, target)?;
+            let i = generator.gen_var_alloc(ctx, int32.into())?;
+            let user_i = generator.gen_store_target(ctx, target)?;
             let (start, end, step) = destructure_range(ctx, iter_val);
             ctx.builder.build_store(i, ctx.builder.build_int_sub(start, step, "start_init"));
             ctx.builder.build_unconditional_branch(test_bb);
@@ -207,6 +208,7 @@ pub fn gen_for<'ctx, 'a, G: CodeGenerator>(
                 "start_loop",
             );
             ctx.builder.build_store(i, tmp);
+            ctx.builder.build_store(user_i, tmp);
             // // if step > 0, continue when i < end
             let cmp1 = ctx.builder.build_int_compare(inkwell::IntPredicate::SLT, tmp, end, "cmp1");
             // if step < 0, continue when i > end
diff --git a/nac3standalone/demo/src/loop.py b/nac3standalone/demo/src/loop.py
new file mode 100644
index 000000000..da353239a
--- /dev/null
+++ b/nac3standalone/demo/src/loop.py
@@ -0,0 +1,9 @@
+@extern
+def output_int32(x: int32):
+    ...
+
+def run() -> int32:
+    for _ in range(10):
+        output_int32(_)
+        _ = 0
+