X-Git-Url: http://git.subgeniuskitty.com/vvhitespace/.git/blobdiff_plain/84c650edec9db1280a29bc2f8121daf7b1ef9731..4fba07dca7fb9275b51e5095a774fe69eeab4660:/vv_interpreter.c

diff --git a/vv_interpreter.c b/vv_interpreter.c
index b816c30..b548a50 100644
--- a/vv_interpreter.c
+++ b/vv_interpreter.c
@@ -120,8 +120,16 @@ parse_label(uint8_t * code, size_t * pc)
         label = label << 1;
         if (c == '\t') label++;
     }
-    // TODO: Where should I handle attempts to access an unitialized label?
-    //       For now, leave it undefined in a nasal demon sense.
+    return label;
+}
+
+uint16_t
+check_label(size_t * labels, uint16_t label, size_t * pc)
+{
+    if (!labels[label]) {
+        fprintf(stderr, "Trying to process label 0x%X.\n", label);
+        ws_die(pc, "uninitialized label (forgot an include?)");
+    }
     return label;
 }
 
@@ -154,14 +162,26 @@ process_imp_stack(uint8_t * code, size_t * pc, int64_t ** sp)
 
                 /* Now, construct the number and push to TOS. */
                 /* I'm assuming the numbers are read MSb first. */
-                int64_t number = 0;
+                uint64_t number = 0; /* Unsigned to accomodate magnitude of most negative number. */
                 uint8_t temp;
                 while ((temp = next_code_byte(code,pc)) != '\n') {
                     if (temp == '\v') ws_die(pc, "non-binary digit in number");
                     number <<= 1;
                     if (temp == '\t') number++;
                 }
-                stack_push(sp, number*sign);
+                /* Without temporarily casting to something >64-bit, the most negative */
+                /* number will overflow when performing 'number*sign'. Instead, we     */
+                /* pick off the most negative number as a special case.                */
+                if (number == (1ULL << 63) && sign == -1) {
+                    /* C parses negative integer literals first as signed positive */
+                    /* integer literals, then applying a unary negation operator.  */
+                    /* Thus, the most negative value is unreachable directly.      */
+                    int64_t number_temp = -9223372036854775807LL; /* First store -((2^63)-1)  */
+                    number_temp--;                                /* Now turn it into -(2^63) */
+                    stack_push(sp, number_temp);
+                } else {
+                    stack_push(sp, number*sign);
+                }
             }
             break;
         case '\n':
@@ -233,7 +253,7 @@ process_imp_arithmetic(uint8_t * code, size_t * pc, int64_t ** sp)
                     case '\t':
                         /* Modulo */
                         temp = stack_pop(sp);
-                        stack_push(sp, stack_pop(sp)%temp);
+                        stack_push(sp, llabs(stack_pop(sp) % llabs(temp)));
                         break;
                     default: ws_die(pc, "malformed arithmetic IMP"); break;
                 }
@@ -266,13 +286,13 @@ process_imp_flowcontrol(uint8_t * code, size_t * pc, int64_t ** sp, size_t * lab
                         break;
                     case '\t':
                         /* Call a subroutine. */
-                        temp_pc = labels[parse_label(code, pc)];
+                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                         *((*rsp)++) = *pc;
                         *pc = temp_pc;
                         break;
                     case '\n':
                         /* Jump unconditionally to a label. */
-                        *pc = labels[parse_label(code, pc)];
+                        *pc = labels[check_label(labels, parse_label(code, pc), pc)];
                         break;
                     default:
                         ws_die(pc, "malformed flow control IMP");
@@ -285,12 +305,12 @@ process_imp_flowcontrol(uint8_t * code, size_t * pc, int64_t ** sp, size_t * lab
                 switch (next_code_byte(code,pc)) {
                     case ' ':
                         /* Jump to a label if TOS == 0 */
-                        temp_pc = labels[parse_label(code, pc)];
+                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                         if (stack_pop(sp) == 0) *pc = temp_pc;
                         break;
                     case '\t':
                         /* Jump to a label if TOS < 0. */
-                        temp_pc = labels[parse_label(code, pc)];
+                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                         if (stack_pop(sp) < 0) *pc = temp_pc;
                         break;
                     case '\n':