preproc: fix list iteration in the case of expand_indirect()

Linked lists where an element may be deleted or substituted during
processing can be subtle to deal with.  Fix the iteration conditions
in this particular case.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/preproc.c b/preproc.c
index 447f235..e83abbe 100644 (file)
--- a/preproc.c
+++ b/preproc.c
@@ -3901,7 +3901,8 @@ static Token *expand_id(Token * tline)
 }
 
 /*
- * Expand indirect tokens, %[...].
+ * Expand indirect tokens, %[...].  Just like expand_smacro(),
+ * the input is considered destroyed.
  */
 static Token *expand_indirect(Token * tline, int level)
 {
@@ -3914,42 +3915,44 @@ static Token *expand_indirect(Token * tline, int level)
        error(ERR_NONFATAL, "interminable indirect expansion");
     } else {
        thead = NULL;
-       for (tp = &tline; (t = *tp); thead = t, tp = &t->next) {
-           if (t->type != TOK_INDIRECT)
-               continue;
-           it = tokenize(t->text);
-           it = expand_indirect(it, level+1);
-           it = expand_smacro(it);
-           while (it) {
-               skip = false;
-               switch (thead ? thead->type : TOK_NONE) {
-               case TOK_WHITESPACE:
-                   skip = (it->type == TOK_WHITESPACE);
-                   break;
-
-               case TOK_ID:
-               case TOK_NUMBER:
-                   if (it->type == thead->type || it->type == TOK_NUMBER) {
-                       char *tmp = nasm_strcat(thead->text, it->text);
-                       thead->text = tmp;
-                       skip = true;
+       tp = &tline;
+       while ((t = *tp)) {
+           if (t->type != TOK_INDIRECT) {
+               thead = t;
+               tp = &t->next;
+           } else {
+               it = tokenize(t->text);
+               it = expand_indirect(it, level+1);
+               it = expand_smacro(it);
+               while (it) {
+                   skip = false;
+                   switch (thead ? thead->type : TOK_NONE) {
+                   case TOK_WHITESPACE:
+                       skip = (it->type == TOK_WHITESPACE);
+                       break;
+                   case TOK_ID:
+                   case TOK_NUMBER:
+                       if (it->type == thead->type || it->type == TOK_NUMBER) {
+                           char *tmp = nasm_strcat(thead->text, it->text);
+                           nasm_free(thead->text);
+                           thead->text = tmp;
+                           skip = true;
+                       }
+                       break;
+                   default:
+                       break;
+                   }
+                   if (skip) {
+                       it = delete_Token(it);
+                   } else {
+                       *tp = thead = it;
+                       tp = &it->next;
+                       it = it->next;
                    }
-                   break;
-                   
-               default:
-                   break;
-               }
-
-               if (skip) {
-                   it = delete_Token(it);
-               } else {
-                   *tp = thead = it;
-                   tp = &it->next;
-                   it = it->next;
                }
+               *tp = thead = t->next;
+               t = delete_Token(t);
            }
-           *tp = t->next;
-           delete_Token(t);
        }
     }
     return tline;