Allow our jumps to be positive or negative

3 files changed, 13 insertions, 13 deletions

diff --git a/src/bytecode/compiler.h b/src/bytecode/compiler.h
index c01f745..27c5ead 100755
--- a/src/bytecode/compiler.h
+++ b/src/bytecode/compiler.h
@@ -46,19 +46,19 @@ emit_constant(Chunk *chunk, Token tok, Object obj) {
 }
 
 size_t
-emit_jump(Chunk *chunk, Token tok, Ops op) {
+emit_jump(Chunk *chunk, Token tok, Ops op, ssize_t offset) {
     add_code(chunk, op, tok.line, tok.column);
-    add_code(chunk, 0xFF, tok.line, tok.column);
-    add_code(chunk, 0xFF, tok.line, tok.column);
+    add_code(chunk, ((u16)offset >> 8) & 0xFF, tok.line, tok.column);
+    add_code(chunk, ((u16)offset) & 0xFF, tok.line, tok.column);
     return array_size(chunk->code) - 2;
 }
 
 void
-patch_jump(Chunk *chunk, size_t offset) {
-  size_t jump = array_size(chunk->code) - offset - 2;
-  assert(jump <= UINT16_MAX && "error: jump is too long");
-  chunk->code[offset] = (jump >> 8) & 0xFF;
-  chunk->code[offset + 1] = (jump) & 0xFF;
+patch_jump(Chunk *chunk, ssize_t offset) {
+  ssize_t jump = array_size(chunk->code) - offset - 2;
+  assert((u16)jump <= UINT16_MAX && "error: jump is too long");
+  chunk->code[offset] = ((u16)jump >> 8) & 0xFF;
+  chunk->code[offset + 1] = ((u16)jump) & 0xFF;
 }
 
 void
@@ -271,7 +271,7 @@ compile_if_op(Chunk *chunk, Visitor *vs, Token start) {
 
     // Condition.
     parse_tree(chunk, vs);
-    size_t jmp_false = emit_jump(chunk, start, OP_JUMP_IF_FALSE);
+    size_t jmp_false = emit_jump(chunk, start, OP_JUMP_IF_FALSE, 0xFFFF);
 
     // True expression.
     parse_tree(chunk, vs);
@@ -284,7 +284,7 @@ compile_if_op(Chunk *chunk, Visitor *vs, Token start) {
     }
 
     // False expression.
-    size_t jmp_end = emit_jump(chunk, start, OP_JUMP);
+    size_t jmp_end = emit_jump(chunk, start, OP_JUMP, 0xFFFF);
     patch_jump(chunk, jmp_false);
     parse_tree(chunk, vs);
     patch_jump(chunk, jmp_end);
diff --git a/src/bytecode/debug.h b/src/bytecode/debug.h
index bc736f9..6703e68 100755
--- a/src/bytecode/debug.h
+++ b/src/bytecode/debug.h
@@ -80,7 +80,7 @@ disassemble_instruction(Chunk *chunk, size_t offset) {
         case OP_JUMP_IF_FALSE: {
             u16 a = chunk->code[offset + 1];
             u16 b = chunk->code[offset + 2];
-            u16 jmp = (a << 8) | b;
+            s16 jmp = (a << 8) | b;
             printf("%-16s %4d\n", ops_str[instruction], jmp);
             return offset + 3;
         } break;
diff --git a/src/bytecode/vm.h b/src/bytecode/vm.h
index ba33077..96e36de 100755
--- a/src/bytecode/vm.h
+++ b/src/bytecode/vm.h
@@ -199,13 +199,13 @@ vm_interpret(VM *vm, Chunk *chunk) {
             case OP_JUMP: {
                 u16 a = *vm->pc++;
                 u16 b = *vm->pc++;
-                u16 offset = (a << 8) | b;
+                s16 offset = (a << 8) | b;
                 vm->pc += offset;
             } break;
             case OP_JUMP_IF_FALSE: {
                 u16 a = *vm->pc++;
                 u16 b = *vm->pc++;
-                u16 offset = (a << 8) | b;
+                s16 offset = (a << 8) | b;
                 if (IS_FALSE(array_pop(vm->stack))) {
                     vm->pc += offset;
                 }