libcpp: __VA_OPT__ tweak

> We want to remove the latter <placemarker> but not the former one, and
> the patch adds the vaopt_padding_tokens counter for it to control
> how many placemarkers are removed on vaopt_state::END.
> As can be seen in #c1 and #c2 of the PR, I've tried various approaches,
> but neither worked out for all the cases except the posted one.

I notice that the second placemarker you mention is avoid_paste, which seems
relevant.  This seems to also work, at least it doesn't seem to break any of
the va_opt tests.

2021-09-01  Jason Merrill  <jason@redhat.com>

	* macro.c (replace_args): When __VA_OPT__ is on the LHS of ##,
	remove trailing avoid_paste tokens.

diff --git a/libcpp/macro.c b/libcpp/macro.c
index b3ba352..f214548 100644 (file)
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -2026,7 +2026,6 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
   i = 0;
   vaopt_state vaopt_tracker (pfile, macro->variadic, &args[macro->paramc - 1]);
   const cpp_token **vaopt_start = NULL;
-  unsigned vaopt_padding_tokens = 0;
   for (src = macro->exp.tokens; src < limit; src++)
     {
       unsigned int arg_tokens_count;
@@ -2059,16 +2058,7 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
              const cpp_token **start = vaopt_start;
              vaopt_start = NULL;
 
-             /* Remove any tail padding from inside the __VA_OPT__.  */
              paste_flag = tokens_buff_last_token_ptr (buff);
-             while (vaopt_padding_tokens--
-                    && paste_flag
-                    && paste_flag != start
-                    && (*paste_flag)->type == CPP_PADDING)
-               {
-                 tokens_buff_remove_last_token (buff);
-                 paste_flag = tokens_buff_last_token_ptr (buff);
-               }
 
              if (vaopt_tracker.stringify ())
                {
@@ -2089,6 +2079,14 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
                }
              else if (src->flags & PASTE_LEFT)
                {
+                 /* Don't avoid paste after all.  */
+                 while (paste_flag && paste_flag != start
+                        && *paste_flag == &pfile->avoid_paste)
+                   {
+                     tokens_buff_remove_last_token (buff);
+                     paste_flag = tokens_buff_last_token_ptr (buff);
+                   }
+
                  /* With a non-empty __VA_OPT__ on the LHS of ##, the last
                     token should be flagged PASTE_LEFT.  */
                  if (paste_flag && (*paste_flag)->type != CPP_PADDING)
@@ -2107,7 +2105,6 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
          continue;
        }
 
-      vaopt_padding_tokens = 0;
       if (src->type != CPP_MACRO_ARG)
        {
          /* Allocate a virtual location for token SRC, and add that
@@ -2263,10 +2260,6 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
 
              index = expanded_token_index (pfile, macro, src, token_index);
              const cpp_token *tok = macro_arg_token_iter_get_token (&from);
-             if (tok->type == CPP_PADDING)
-               vaopt_padding_tokens++;
-             else
-               vaopt_padding_tokens = 0;
              tokens_buff_add_token (buff, virt_locs, tok,
                                     macro_arg_token_iter_get_location (&from),
                                     src->src_loc, map, index);
@@ -2313,7 +2306,6 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
          tokens_buff_add_token (buff, virt_locs,
                                 t, t->src_loc, t->src_loc,
                                 NULL, 0);
-         vaopt_padding_tokens++;
        }
 
       /* Add a new paste flag, or remove an unwanted one.  */