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libcpp: Fix up padding handling in funlike_invocation_p [PR104147]

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As mentioned in the PR, in some cases we preprocess incorrectly when we
encounter an identifier which is defined as function-like macro, followed
by at least 2 CPP_PADDING tokens and then some other identifier.
On the following testcase, the problem is in the 3rd funlike_invocation_p,
the tokens are CPP_NAME Y, CPP_PADDING (the pfile->avoid_paste shared token),
CPP_PADDING (one created with padding_token, val.source is non-NULL and
val.source->flags & PREV_WHITE is non-zero) and then another CPP_NAME.
funlike_invocation_p remembers there was a padding token, but remembers the
first one because of its condition, then the next token is the CPP_NAME,
which is not CPP_OPEN_PAREN, so the CPP_NAME token is backed up, but as we
can't easily backup more tokens, it pushes into a new context the padding
token (the pfile->avoid_paste one).  The net effect is that when Y is not
defined as fun-like macro, we read Y, avoid_paste, padding_token, Y,
while if Y is fun-like macro, we read Y, avoid_paste, avoid_paste, Y
(the second avoid_paste is because that is how we handle end of a context).
Now, for stringify_arg that is unfortunately a significant difference,
which handles CPP_PADDING tokens with:
      if (token->type == CPP_PADDING)
        {
          if (source == NULL
              || (!(source->flags & PREV_WHITE)
                  && token->val.source == NULL))
            source = token->val.source;
          continue;
        }
and later on
      /* Leading white space?  */
      if (dest - 1 != BUFF_FRONT (pfile->u_buff))
        {
          if (source == NULL)
            source = token;
          if (source->flags & PREV_WHITE)
            *dest++ = ' ';
        }
      source = NULL;
(and c-ppoutput.cc has similar code).
So, when Y is not fun-like macro, ' ' is added because padding_token's
val.source->flags & PREV_WHITE is non-zero, while when it is fun-like
macro, we don't add ' ' in between, because source is NULL and so
used from the next token (CPP_NAME Y), which doesn't have PREV_WHITE set.

Now, the funlike_invocation_p condition
       if (padding == NULL
           || (!(padding->flags & PREV_WHITE) && token->val.source == NULL))
        padding = token;
looks very similar to that in stringify_arg/c-ppoutput.cc, so I assume
the intent was to prefer do the same thing and pick the right padding.
But there are significant differences.  Both stringify_arg and c-ppoutput.cc
don't remember the CPP_PADDING token, but its val.source instead, while
in funlike_invocation_p we want to remember the padding token that has the
significant information for stringify_arg/c-ppoutput.cc.
So, IMHO we want to overwrite padding if:
1) padding == NULL (remember that there was any padding at all)
2) padding->val.source == NULL (this matches the source == NULL
   case in stringify_arg)
3) !(padding->val.source->flags & PREV_WHITE) && token->val.source == NULL
   (this matches the !(source->flags & PREV_WHITE) && token->val.source == NULL
   case in stringify_arg)

2022-02-01  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/104147
	* macro.cc (funlike_invocation_p): For padding prefer a token
	with val.source non-NULL especially if it has PREV_WHITE set
	on val.source->flags.  Add gcc_assert that CPP_PADDING tokens
	don't have PREV_WHITE set in flags.

	* c-c++-common/cpp/pr104147.c: New test.
This commit is contained in:
Jakub Jelinek 2022-02-01 20:48:03 +01:00
parent efc46b550f
commit 95ac563540
2 changed files with 31 additions and 1 deletions
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27
gcc/testsuite/c-c++-common/cpp/pr104147.c Normal file
View file

@ -0,0 +1,27 @@
/* PR preprocessor/104147 */
/* { dg-do run } */
#define X(x,y) x y
#define STR_(x) #x
#define STR(x) STR_(x)
const char *str =
STR(X(Y,Y))
#define Y()
STR(X(Y,Y))
#undef Y
STR(X(Y,Y))
#define Y()
STR(X(Y,Y))
STR(X(Y,
Y))
STR(X(Y
,Y))
;
int
main ()
{
if (__builtin_strcmp (str, "Y YY YY YY YY YY Y") != 0)
__builtin_abort ();
return 0;
}

5
libcpp/macro.cc
View file

@ -1373,8 +1373,11 @@ funlike_invocation_p (cpp_reader *pfile, cpp_hashnode *node,
token = cpp_get_token (pfile);
if (token->type != CPP_PADDING)
break;
gcc_assert ((token->flags & PREV_WHITE) == 0);
if (padding == NULL
|| (!(padding->flags & PREV_WHITE) && token->val.source == NULL))
|| padding->val.source == NULL
|| (!(padding->val.source->flags & PREV_WHITE)
&& token->val.source == NULL))
padding = token;
}