libcpp: Fix up #__VA_OPT__ handling [PR103415]

stringify_arg uses pfile->u_buff to create the string literal.
Unfortunately, paste_tokens -> _cpp_lex_direct -> lex_number -> _cpp_unaligned_alloc
can in some cases use pfile->u_buff too, which results in losing everything
prepared for the string literal until the token pasting.

The following patch fixes that by not calling paste_token during the
construction of the string literal, but doing that before.  All the tokens
we are processing have been pushed into a token buffer using
tokens_buff_add_token so it is fine if we paste some of them in that buffer
(successful pasting creates a new token in that buffer), move following
tokens if any to make it contiguous, pop (throw away) the extra tokens at
the end and then do stringify_arg.

Also, paste_tokens now copies over PREV_WHITE and PREV_FALLTHROUGH flags
from the original lhs token to the replacement token.  Copying that way
the PREV_WHITE flag is needed for the #__VA_OPT__ handling and copying
over PREV_FALLTHROUGH fixes the new Wimplicit-fallthrough-38.c test.

2021-12-01  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/103415
libcpp/
	* macro.c (stringify_arg): Remove va_opt argument and va_opt handling.
	(paste_tokens): On successful paste or in PREV_WHITE and
	PREV_FALLTHROUGH flags from the *plhs token to the new token.
	(replace_args): Adjust stringify_arg callers.  For #__VA_OPT__,
	perform token pasting in a separate loop before stringify_arg call.
gcc/testsuite/
	* c-c++-common/cpp/va-opt-8.c: New test.
	* c-c++-common/Wimplicit-fallthrough-38.c: New test.

diff --git a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-38.c b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-38.c
new file mode 100644 (file)
index 0000000..80f7d45
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-38.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=3" } */
+
+#define FOO \
+int                            \
+foo (int a)                    \
+{                              \
+  switch (a)                   \
+    {                          \
+    case 1:                    \
+      ++a;                     \
+      /* FALLTHRU */           \
+    case 2:                    \
+      ++a;                     \
+      /* FALLTHRU */           \
+    ca##se 3:                  \
+      ++a;                     \
+    default:                   \
+      break;                   \
+    }                          \
+  return a;                    \
+}
+
+FOO

diff --git a/gcc/testsuite/c-c++-common/cpp/va-opt-8.c b/gcc/testsuite/c-c++-common/cpp/va-opt-8.c
new file mode 100644 (file)
index 0000000..583ebf0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/va-opt-8.c
@@ -0,0 +1,18 @@
+/* PR preprocessor/103415 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu99" { target c } } */
+/* { dg-options "-std=c++20" { target c++ } } */
+
+#define n(x, ...) = #__VA_OPT__(x##3)
+#define o(x, ...) #__VA_OPT__(x##__VA_ARGS__##9)
+const char *c n(1 2, 4);
+const char *d = o(5  6, 7      8);
+
+int
+main ()
+{
+  if (__builtin_strcmp (c, "1 23")
+      || __builtin_strcmp (d, "5 67 89"))
+    __builtin_abort ();
+  return 0;
+}

diff --git a/libcpp/macro.c b/libcpp/macro.c
index 95e5b8be8d51c8fd09ecf66921aef164dcd01348..6269c1570d36a055ebf31ec0df3ddd0192040d17 100644 (file)
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -295,7 +295,7 @@ static cpp_context *next_context (cpp_reader *);
 static const cpp_token *padding_token (cpp_reader *, const cpp_token *);
 static const cpp_token *new_string_token (cpp_reader *, uchar *, unsigned int);
 static const cpp_token *stringify_arg (cpp_reader *, const cpp_token **,
-                                      unsigned int, bool);
+                                      unsigned int);
 static void paste_all_tokens (cpp_reader *, const cpp_token *);
 static bool paste_tokens (cpp_reader *, location_t,
                          const cpp_token **, const cpp_token *);
@@ -834,8 +834,7 @@ cpp_quote_string (uchar *dest, const uchar *src, unsigned int len)
 /* Convert a token sequence FIRST to FIRST+COUNT-1 to a single string token
    according to the rules of the ISO C #-operator.  */
 static const cpp_token *
-stringify_arg (cpp_reader *pfile, const cpp_token **first, unsigned int count,
-              bool va_opt)
+stringify_arg (cpp_reader *pfile, const cpp_token **first, unsigned int count)
 {
   unsigned char *dest;
   unsigned int i, escape_it, backslash_count = 0;
@@ -852,24 +851,6 @@ stringify_arg (cpp_reader *pfile, const cpp_token **first, unsigned int count,
     {
       const cpp_token *token = first[i];
 
-      if (va_opt && (token->flags & PASTE_LEFT))
-       {
-         location_t virt_loc = pfile->invocation_location;
-         const cpp_token *rhs;
-         do
-           {
-             if (i == count)
-               abort ();
-             rhs = first[++i];
-             if (!paste_tokens (pfile, virt_loc, &token, rhs))
-               {
-                 --i;
-                 break;
-               }
-           }
-         while (rhs->flags & PASTE_LEFT);
-       }
-
       if (token->type == CPP_PADDING)
        {
          if (source == NULL
@@ -1003,6 +984,7 @@ paste_tokens (cpp_reader *pfile, location_t location,
       return false;
     }
 
+  lhs->flags |= (*plhs)->flags & (PREV_WHITE | PREV_FALLTHROUGH);
   *plhs = lhs;
   _cpp_pop_buffer (pfile);
   return true;
@@ -1945,8 +1927,7 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
        if (src->flags & STRINGIFY_ARG)
          {
            if (!arg->stringified)
-             arg->stringified = stringify_arg (pfile, arg->first, arg->count,
-                                               false);
+             arg->stringified = stringify_arg (pfile, arg->first, arg->count);
          }
        else if ((src->flags & PASTE_LEFT)
                 || (src != macro->exp.tokens && (src[-1].flags & PASTE_LEFT)))
@@ -2066,11 +2047,46 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
                {
                  unsigned int count
                    = start ? paste_flag - start : tokens_buff_count (buff);
-                 const cpp_token *t
-                   = stringify_arg (pfile,
-                                    start ? start + 1
-                                    : (const cpp_token **) (buff->base),
-                                    count, true);
+                 const cpp_token **first
+                   = start ? start + 1
+                           : (const cpp_token **) (buff->base);
+                 unsigned int i, j;
+
+                 /* Paste any tokens that need to be pasted before calling
+                    stringify_arg, because stringify_arg uses pfile->u_buff
+                    which paste_tokens can use as well.  */
+                 for (i = 0, j = 0; i < count; i++, j++)
+                   {
+                     const cpp_token *token = first[i];
+
+                     if (token->flags & PASTE_LEFT)
+                       {
+                         location_t virt_loc = pfile->invocation_location;
+                         const cpp_token *rhs;
+                         do
+                           {
+                             if (i == count)
+                               abort ();
+                             rhs = first[++i];
+                             if (!paste_tokens (pfile, virt_loc, &token, rhs))
+                               {
+                                 --i;
+                                 break;
+                               }
+                           }
+                         while (rhs->flags & PASTE_LEFT);
+                       }
+
+                     first[j] = token;
+                   }
+                 if (j != i)
+                   {
+                     while (i-- != j)
+                       tokens_buff_remove_last_token (buff);
+                     count = j;
+                   }
+
+                 const cpp_token *t = stringify_arg (pfile, first, count);
                  while (count--)
                    tokens_buff_remove_last_token (buff);
                  if (src->flags & PASTE_LEFT)