add resolve label in builder and reformat

Author: hellerve

docs/builder.md

@@ -30,6 +30,8 @@ around abi registers, stack setup, and label plumbing, and it looks less scary.
 - `cj_builder_call_unary(ctx, scratch, label, arg)`: loads the first argument
   register, emits the right call/bl, and—when a scratch stack is supplied—moves
   the return value into a fresh scratch slot.
+- `cj_resolve_label(ctx, module, label)`: convert a recorded label to a
+  callable pointer after finalization.
 
 ## control flow
 

examples/minilang.c

@@ -398,8 +398,8 @@ int main(void)
 
   for (int i = 0; i < function_count; ++i)
   {
-    size_t offset = cj->label_positions[functions[i].entry.id];
-    functions[i].fn = (int (*)(int))((uint8_t *)(void *)module + offset);
+    void *addr = cj_resolve_label(cj, module, functions[i].entry);
+    functions[i].fn = (int (*)(int))addr;
   }
 
   printf("minilang demo:\n");

src/builder.h

@@ -84,9 +84,8 @@ static inline cj_operand cj_builder_scratch_acquire(cj_builder_scratch *scratch)
 static inline void cj_builder_scratch_release(cj_builder_scratch *scratch);
 static inline unsigned cj_builder_arg_int_capacity(void);
 static inline void cj_builder_call_label(cj_ctx *ctx, cj_label target);
-static inline cj_operand
-cj_builder_call(cj_ctx *ctx, cj_builder_scratch *scratch, cj_label target,
-                const cj_operand *args, size_t arg_count);
+static inline cj_operand cj_builder_call(cj_ctx *ctx, cj_builder_scratch *scratch, cj_label target,
+                                         const cj_operand *args, size_t arg_count);
 static inline cj_operand cj_builder_call_unary(cj_ctx *ctx, cj_builder_scratch *scratch,
                                                cj_label target, cj_operand arg0);
 
@@ -640,9 +639,8 @@ static inline cj_operand cj_builder_call_unary(cj_ctx *ctx, cj_builder_scratch *
   return cj_builder_call(ctx, scratch, target, args, 1);
 }
 
-static inline cj_operand
-cj_builder_call(cj_ctx *ctx, cj_builder_scratch *scratch, cj_label target,
-                const cj_operand *args, size_t arg_count)
+static inline cj_operand cj_builder_call(cj_ctx *ctx, cj_builder_scratch *scratch, cj_label target,
+                                         const cj_operand *args, size_t arg_count)
 {
   if (!ctx)
     return cj_builder_return_reg();

src/ctx.c

@@ -285,3 +285,19 @@ void cj_emit_x86_rel(cj_ctx *ctx, const uint8_t *opcode, size_t opcode_len, uint
     ctx->num_fixups++;
   }
 }
+
+void *cj_resolve_label(const cj_ctx *ctx, cj_fn module, cj_label label)
+{
+  if (!ctx || !module)
+    return NULL;
+
+  if (label.id < 0 || label.id >= ctx->num_labels)
+    return NULL;
+
+  uint64_t pos = ctx->label_positions[label.id];
+  if (pos == UINT64_MAX)
+    return NULL;
+
+  uint8_t *base = (uint8_t *)(void *)module;
+  return (void *)(base + pos);
+}

src/ctx.h

@@ -67,3 +67,4 @@ void cj_emit_branch(cj_ctx *ctx, uint32_t base_instr, cj_label label, uint8_t of
                     uint8_t offset_shift);
 void cj_emit_x86_rel(cj_ctx *ctx, const uint8_t *opcode, size_t opcode_len, uint8_t disp_width,
                      cj_label label);
+void *cj_resolve_label(const cj_ctx *ctx, cj_fn module, cj_label label);

tests/test_harness_builder.c

@@ -100,8 +100,7 @@ static void test_call_helper(void)
   cj_fn module = create_cj_fn(cj);
   assert(module);
 
-  size_t entry_offset = cj->label_positions[entry.id];
-  fn1_t fn = (fn1_t)((uint8_t *)(void *)module + entry_offset);
+  fn1_t fn = (fn1_t)cj_resolve_label(cj, module, entry);
   assert(fn);
   assert(fn(10) == 13);
   assert(fn(-4) == -1);