From 592204e6ee0961de116cffbf02a4cfd85b55443b Mon Sep 17 00:00:00 2001
From: tyfkda <tyfkda@gmail.com>
Date: Tue, 23 Apr 2024 09:01:33 +0900
Subject: [PATCH] Prevent assigning to cast expression

`_Bool`
---
 src/cc/backend/codegen_expr.c |  3 +++
 src/cc/frontend/parser_expr.c |  6 +++++-
 src/wcc/gen_wasm.c            | 11 +++++++++--
 tests/test.sh                 |  1 +
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/cc/backend/codegen_expr.c b/src/cc/backend/codegen_expr.c
index b687f8a20..3cbe85169 100644
--- a/src/cc/backend/codegen_expr.c
+++ b/src/cc/backend/codegen_expr.c
@@ -165,6 +165,9 @@ void gen_cond_jmp(Expr *cond, bool tf, BB *bb) {
 static VReg *gen_cast(Expr *expr) {
   Expr *src = expr->unary.sub;
   Type *dst_type = expr->type;
+  if (is_bool(dst_type))
+    return gen_expr(make_cond(src));
+
   int dst_size = type_size(dst_type);
 #if XCC_TARGET_ARCH == XCC_ARCH_X64 && !defined(__NO_FLONUM)
   // On x64, cannot cast from double to uint64_t directly.
diff --git a/src/cc/frontend/parser_expr.c b/src/cc/frontend/parser_expr.c
index 1220f735c..f64f8830b 100644
--- a/src/cc/frontend/parser_expr.c
+++ b/src/cc/frontend/parser_expr.c
@@ -1007,7 +1007,11 @@ static Expr *parse_cast_expr(void) {
       Expr *sub = parse_cast_expr();
       sub = str_to_char_array_var(curscope, sub);
       check_cast(type, sub->type, is_zero(sub), true, token);
-      if (type->kind != TY_VOID && (is_const(sub) || is_bool(type)))
+
+      // Do not reduce cast expression using `make_cast`
+      // because it ignores `(int)x = 1`.
+
+      if (type->kind != TY_VOID && is_const(sub))
         return make_cast(type, token, sub, true);
       return sub->type->kind != TY_VOID ? new_expr_cast(type, token, sub) : sub;
     }
diff --git a/src/wcc/gen_wasm.c b/src/wcc/gen_wasm.c
index 85b74705d..94eefa254 100644
--- a/src/wcc/gen_wasm.c
+++ b/src/wcc/gen_wasm.c
@@ -863,9 +863,16 @@ static void gen_comma(Expr *expr, bool needval) {
 }
 
 static void gen_cast(Expr *expr, bool needval) {
-  gen_expr(expr->unary.sub, needval);
+  Expr *src = expr->unary.sub;
+  Type *dst_type = expr->type;
+  if (is_bool(dst_type)) {
+    gen_expr(make_cond(src), needval);
+    return;
+  }
+
+  gen_expr(src, needval);
   if (needval)
-    gen_cast_to(expr->type, expr->unary.sub->type);
+    gen_cast_to(dst_type, src->type);
 }
 
 static void gen_ref(Expr *expr, bool needval) {
diff --git a/tests/test.sh b/tests/test.sh
index 8ad9fc77a..87f515ecd 100755
--- a/tests/test.sh
+++ b/tests/test.sh
@@ -265,6 +265,7 @@ test_error() {
   compile_error 'dup enum elem' 'enum Foo { BAR, BAR }; void main(){}'
   compile_error '+x =' 'void main(){ int x; +x = 45; }'
   compile_error '(int)x = ' 'void main(){ int x; (int)x = 32; }'
+  compile_error '(_Bool)x = ' 'void main(){ _Bool x; (_Bool)x = 32; }'
   compile_error 'compound literal =' 'struct Foo {int x;}; void main(){ struct Foo foo = {1}; (struct Foo){66} = foo; }'
   compile_error 'compound literal w/o brace' 'void main(){ ++(int)55; }'
   compile_error 'param and first scope' 'void main(int x){ int x; }'