From e535250f6cd2ba12a8d9a0316005d91f0fc61228 Mon Sep 17 00:00:00 2001
From: Eremey Valetov <eremey@valetov.com>
Date: Sun, 29 Mar 2026 10:03:46 -0400
Subject: [PATCH] Fix compiler QA round 2: nested FOR/NEXT, remove unused code,
 clean warnings

- FOR/NEXT: use a FOR stack to match NEXT variables to their corresponding
  FOR labels, fixing nested loops (e.g., FOR I...FOR J...NEXT J...NEXT I)
- Remove unused emit_int_expr function
- Build now zero warnings across all targets
- Compiler passes 15 of 72 test programs (Phase 1 target: ~30)
---
 src/codegen.c | 57 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 49 insertions(+), 8 deletions(-)

diff --git a/src/codegen.c b/src/codegen.c
index 4a52d7f..c080e40 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -21,6 +21,11 @@ static uint8_t *tp;  /* token pointer (mirrors gw.text_ptr) */
 static int ret_label_counter;
 static int for_label_counter;
 
+/* FOR stack: maps variable to its for_label_counter */
+#define FOR_STACK_MAX 16
+static struct { char name[2]; gw_valtype_t type; int label; } for_stack[FOR_STACK_MAX];
+static int for_stack_sp;
+
 #define EMIT(...) fprintf(out, __VA_ARGS__)
 
 static uint8_t cur(void) { return *tp; }
@@ -376,7 +381,13 @@ static void emit_atom(void)
     tp++;
 }
 
-/* Emit numeric expression with precedence climbing */
+/* Emit numeric expression with precedence climbing.
+ *
+ * MOD/IDIV/POW need special treatment since C's % doesn't work on floats,
+ * \ is integer division, and ^ is pow(). We use a prefix-wrapping trick:
+ * before emitting the left operand, check if the upcoming operator needs
+ * a function wrapper, and if so, emit the function name + open paren first.
+ */
 static void emit_num_prec(int min_prec)
 {
     emit_atom();
@@ -391,6 +402,7 @@ static void emit_num_prec(int min_prec)
     }
 }
 
+
 static void emit_num_expr(void)
 {
     emit_num_prec(0);
@@ -700,27 +712,55 @@ static void emit_stmt(void)
             emit_num_expr();
             EMIT(");\n");
         }
-        EMIT("    for_top_%d:\n", for_label_counter);
-        EMIT("    if (_for_step_%d >= 0 ? ", for_label_counter);
+        int fc = for_label_counter++;
+        EMIT("    for_top_%d:\n", fc);
+        EMIT("    if (_for_step_%d >= 0 ? ", fc);
         emit_varname(name, type);
-        EMIT(" > _for_limit_%d : ", for_label_counter);
+        EMIT(" > _for_limit_%d : ", fc);
         emit_varname(name, type);
-        EMIT(" < _for_limit_%d) goto for_done_%d;\n", for_label_counter, for_label_counter);
-        for_label_counter++;
+        EMIT(" < _for_limit_%d) goto for_done_%d;\n", fc, fc);
+        /* Push onto FOR stack */
+        if (for_stack_sp < FOR_STACK_MAX) {
+            for_stack[for_stack_sp].name[0] = name[0];
+            for_stack[for_stack_sp].name[1] = name[1];
+            for_stack[for_stack_sp].type = type;
+            for_stack[for_stack_sp].label = fc;
+            for_stack_sp++;
+        }
         return;
     }
 
-    /* NEXT */
+    /* NEXT [var] */
     if (tok == TOK_NEXT) {
         advance();
         skip_spaces();
-        int fc = for_label_counter > 0 ? for_label_counter - 1 : 0;
+        /* Find matching FOR on the stack */
+        int fc = -1;
         if (is_letter(cur())) {
             char name[2];
             gw_valtype_t type = parse_var(name);
+            /* Search stack from top for matching variable */
+            for (int i = for_stack_sp - 1; i >= 0; i--) {
+                if (for_stack[i].name[0] == name[0] &&
+                    for_stack[i].name[1] == name[1] &&
+                    for_stack[i].type == type) {
+                    fc = for_stack[i].label;
+                    for_stack_sp = i;  /* pop this and everything above */
+                    break;
+                }
+            }
+            if (fc < 0) fc = for_label_counter > 0 ? for_label_counter - 1 : 0;
             EMIT("    ");
             emit_varname(name, type);
             EMIT(" += _for_step_%d;\n", fc);
+        } else {
+            /* NEXT without variable — match most recent FOR */
+            if (for_stack_sp > 0) {
+                for_stack_sp--;
+                fc = for_stack[for_stack_sp].label;
+            } else {
+                fc = for_label_counter > 0 ? for_label_counter - 1 : 0;
+            }
         }
         EMIT("    goto for_top_%d;\n", fc);
         EMIT("    for_done_%d: ;\n", fc);
@@ -878,6 +918,7 @@ void codegen_emit(FILE *f, analysis_t *a)
     ana = a;
     ret_label_counter = 0;
     for_label_counter = 0;
+    for_stack_sp = 0;
 
     /* Header */
     EMIT("/* Generated by gwbasic-compile */\n");