redesign parse function to take a dice as parameter

Otherwise we couldn't fetch any error message or code if the dice
object is never visible to the user.

lib/dice.c

@@ -44,7 +44,7 @@ struct dice_
     char *error;
 };
 
-static dice_t dice_new(void)
+dice_t dice_new(void)
 {
     dice_t tmp = calloc(1, sizeof(struct dice_));
 
@@ -101,16 +101,14 @@ dice_t dice_simple(uint32_t amount, uint32_t sides)
     return tmp;
 }
 
-dice_t dice_parse(char const *s)
+bool dice_parse(dice_t d, char const *s)
 {
     void *scanner = NULL;
-    dice_t d = NULL;
     void *buffer = NULL;
     int ret = 0;
 
-    d = dice_new();
-    if (d == NULL) {
-        return NULL;
+    if (d == NULL || s == NULL) {
+        return false;
     }
 
     yylex_init_extra(d, &scanner);
@@ -123,11 +121,10 @@ dice_t dice_parse(char const *s)
     yylex_destroy(scanner);
 
     if (ret) {
-        dice_free(d);
-        return NULL;
+        return false;
     }
 
-    return d;
+    return true;
 }
 
 bool dice_set(dice_t d, dice_option_t opt, ...)

lib/dice.h

@@ -44,9 +44,10 @@ typedef enum {
 void dice_result_free(dice_result_t *r);
 void dice_result_freev(dice_result_t *r, size_t len);
 
+dice_t dice_new(void);
 void dice_free(dice_t t);
 dice_t dice_simple(uint32_t amount, uint32_t sides);
-dice_t dice_parse(char const *s);
+bool dice_parse(dice_t d, char const *s);
 
 bool dice_set(dice_t d, dice_option_t opt, ...);
 bool dice_get(dice_t d, dice_option_t opt, ...);

lib/diceexpr.c

@@ -279,13 +279,15 @@ void next_token(state *s) {
         if (isdigit(s->next[0]) || s->next[0] == '.' || s->next[0] == 'd') {
             /* first try reading a dice expression, if that fails, we go
                back to trying a number instead */
-            dice_t d = dice_parse(s->next);
-            if (d != NULL) {
+            dice_t d = dice_new();
+
+            if (dice_parse(d, s->next)) {
                 int consumed = dice_consumed(d);
                 s->type = TOK_DICE;
                 s->dice = d;
                 s->next += consumed;
-            } else if (d == NULL) {
+            } else {
+                dice_free(d);
                 /* Try reading a number. */
                 s->value = strtod(s->next, (char**)&s->next);
                 s->type = TOK_NUMBER;