libcpp: Handle extended characters in user-defined literal suffix [PR103902]

The PR complains that we do not handle UTF-8 in the suffix for a user-defined
literal, such as:

bool operator ""_π (unsigned long long);

In fact we don't handle any extended identifier characters there, whether
UTF-8, UCNs, or the $ sign. We do handle it fine if the optional space after
the "" tokens is included, since then the identifier is lexed in the
"normal" way as its own token. But when it is lexed as part of the string
token, this is handled in lex_string() with a one-off loop that is not aware
of extended characters.

This patch fixes it by adding a new function scan_cur_identifier() that can
be used to lex an identifier while in the middle of lexing another token.

BTW, the other place that has been mis-lexing identifiers is
lex_identifier_intern(), which is used to implement #pragma push_macro
and #pragma pop_macro. This does not support extended characters either.
I will add that in a subsequent patch, because it can't directly reuse the
new function, but rather needs to lex from a string instead of a cpp_buffer.

With scan_cur_identifier(), we do also correctly warn about bidi and
normalization issues in the extended identifiers comprising the suffix.

libcpp/ChangeLog:

	PR preprocessor/103902
	* lex.cc (identifier_diagnostics_on_lex): New function refactoring
	some common code.
	(lex_identifier_intern): Use the new function.
	(lex_identifier): Don't run identifier diagnostics here, rather let
	the call site do it when needed.
	(_cpp_lex_direct): Adjust the call sites of lex_identifier ()
	acccordingly.
	(struct scan_id_result): New struct.
	(scan_cur_identifier): New function.
	(create_literal2): New function.
	(lit_accum::create_literal2): New function.
	(is_macro): Folded into new function...
	(maybe_ignore_udl_macro_suffix): ...here.
	(is_macro_not_literal_suffix): Folded likewise.
	(lex_raw_string): Handle UTF-8 in UDL suffix via
	scan_cur_identifier ().
	(lex_string): Likewise.

gcc/testsuite/ChangeLog:

	PR preprocessor/103902
	* g++.dg/cpp0x/udlit-extended-id-1.C: New test.
	* g++.dg/cpp0x/udlit-extended-id-2.C: New test.
	* g++.dg/cpp0x/udlit-extended-id-3.C: New test.
	* g++.dg/cpp0x/udlit-extended-id-4.C: New test.

1 files changed, 215 insertions, 167 deletions

diff --git a/libcpp/lex.cc b/libcpp/lex.cc
index 45ea16a..8dea4d3 100644
--- a/libcpp/lex.cc
+++ b/libcpp/lex.cc
@@ -2057,8 +2057,11 @@ warn_about_normalization (cpp_reader *pfile,
     }
 }
 
-/* Returns TRUE if the sequence starting at buffer->cur is valid in
-   an identifier.  FIRST is TRUE if this starts an identifier.  */
+/* Returns TRUE if the byte sequence starting at buffer->cur is a valid
+   extended character in an identifier.  If FIRST is TRUE, then the character
+   must be valid at the beginning of an identifier as well.  If the return
+   value is TRUE, then pfile->buffer->cur has been moved to point to the next
+   byte after the extended character.  */
 
 static bool
 forms_identifier_p (cpp_reader *pfile, int first,
@@ -2154,6 +2157,47 @@ maybe_va_opt_error (cpp_reader *pfile)
     }
 }
 
+/* Helper function to perform diagnostics that are needed (rarely)
+   when an identifier is lexed.  */
+static void
+identifier_diagnostics_on_lex (cpp_reader *pfile, cpp_hashnode *node)
+{
+  if (__builtin_expect (!(node->flags & NODE_DIAGNOSTIC)
+			|| pfile->state.skipping, 1))
+    return;
+
+  /* It is allowed to poison the same identifier twice.  */
+  if ((node->flags & NODE_POISONED) && !pfile->state.poisoned_ok)
+    cpp_error (pfile, CPP_DL_ERROR, "attempt to use poisoned \"%s\"",
+	       NODE_NAME (node));
+
+  /* Constraint 6.10.3.5: __VA_ARGS__ should only appear in the
+     replacement list of a variadic macro.  */
+  if (node == pfile->spec_nodes.n__VA_ARGS__
+      && !pfile->state.va_args_ok)
+    {
+      if (CPP_OPTION (pfile, cplusplus))
+	cpp_error (pfile, CPP_DL_PEDWARN,
+		   "__VA_ARGS__ can only appear in the expansion"
+		   " of a C++11 variadic macro");
+      else
+	cpp_error (pfile, CPP_DL_PEDWARN,
+		   "__VA_ARGS__ can only appear in the expansion"
+		   " of a C99 variadic macro");
+    }
+
+  /* __VA_OPT__ should only appear in the replacement list of a
+     variadic macro.  */
+  if (node == pfile->spec_nodes.n__VA_OPT__)
+    maybe_va_opt_error (pfile);
+
+  /* For -Wc++-compat, warn about use of C++ named operators.  */
+  if (node->flags & NODE_WARN_OPERATOR)
+    cpp_warning (pfile, CPP_W_CXX_OPERATOR_NAMES,
+		 "identifier \"%s\" is a special operator name in C++",
+		 NODE_NAME (node));
+}
+
 /* Helper function to get the cpp_hashnode of the identifier BASE.  */
 static cpp_hashnode *
 lex_identifier_intern (cpp_reader *pfile, const uchar *base)
@@ -2173,41 +2217,7 @@ lex_identifier_intern (cpp_reader *pfile, const uchar *base)
   hash = HT_HASHFINISH (hash, len);
   result = CPP_HASHNODE (ht_lookup_with_hash (pfile->hash_table,
 					      base, len, hash, HT_ALLOC));
-
-  /* Rarely, identifiers require diagnostics when lexed.  */
-  if (__builtin_expect ((result->flags & NODE_DIAGNOSTIC)
-			&& !pfile->state.skipping, 0))
-    {
-      /* It is allowed to poison the same identifier twice.  */
-      if ((result->flags & NODE_POISONED) && !pfile->state.poisoned_ok)
-	cpp_error (pfile, CPP_DL_ERROR, "attempt to use poisoned \"%s\"",
-		   NODE_NAME (result));
-
-      /* Constraint 6.10.3.5: __VA_ARGS__ should only appear in the
-	 replacement list of a variadic macro.  */
-      if (result == pfile->spec_nodes.n__VA_ARGS__
-	  && !pfile->state.va_args_ok)
-	{
-	  if (CPP_OPTION (pfile, cplusplus))
-	    cpp_error (pfile, CPP_DL_PEDWARN,
-		       "__VA_ARGS__ can only appear in the expansion"
-		       " of a C++11 variadic macro");
-	  else
-	    cpp_error (pfile, CPP_DL_PEDWARN,
-		       "__VA_ARGS__ can only appear in the expansion"
-		       " of a C99 variadic macro");
-	}
-
-      if (result == pfile->spec_nodes.n__VA_OPT__)
-	maybe_va_opt_error (pfile);
-
-      /* For -Wc++-compat, warn about use of C++ named operators.  */
-      if (result->flags & NODE_WARN_OPERATOR)
-	cpp_warning (pfile, CPP_W_CXX_OPERATOR_NAMES,
-		     "identifier \"%s\" is a special operator name in C++",
-		     NODE_NAME (result));
-    }
-
+  identifier_diagnostics_on_lex (pfile, result);
   return result;
 }
 
@@ -2221,7 +2231,9 @@ _cpp_lex_identifier (cpp_reader *pfile, const char *name)
   return result;
 }
 
-/* Lex an identifier starting at BUFFER->CUR - 1.  */
+/* Lex an identifier starting at BASE.  BUFFER->CUR is expected to point
+   one past the first character at BASE, which may be a (possibly multi-byte)
+   character if STARTS_UCN is true.  */
 static cpp_hashnode *
 lex_identifier (cpp_reader *pfile, const uchar *base, bool starts_ucn,
 		struct normalize_state *nst, cpp_hashnode **spelling)
@@ -2270,42 +2282,51 @@ lex_identifier (cpp_reader *pfile, const uchar *base, bool starts_ucn,
       *spelling = result;
     }
 
-  /* Rarely, identifiers require diagnostics when lexed.  */
-  if (__builtin_expect ((result->flags & NODE_DIAGNOSTIC)
-			&& !pfile->state.skipping, 0))
-    {
-      /* It is allowed to poison the same identifier twice.  */
-      if ((result->flags & NODE_POISONED) && !pfile->state.poisoned_ok)
-	cpp_error (pfile, CPP_DL_ERROR, "attempt to use poisoned \"%s\"",
-		   NODE_NAME (result));
-
-      /* Constraint 6.10.3.5: __VA_ARGS__ should only appear in the
-	 replacement list of a variadic macro.  */
-      if (result == pfile->spec_nodes.n__VA_ARGS__
-	  && !pfile->state.va_args_ok)
-	{
-	  if (CPP_OPTION (pfile, cplusplus))
-	    cpp_error (pfile, CPP_DL_PEDWARN,
-		       "__VA_ARGS__ can only appear in the expansion"
-		       " of a C++11 variadic macro");
-	  else
-	    cpp_error (pfile, CPP_DL_PEDWARN,
-		       "__VA_ARGS__ can only appear in the expansion"
-		       " of a C99 variadic macro");
-	}
+  return result;
+}
 
-      /* __VA_OPT__ should only appear in the replacement list of a
-	 variadic macro.  */
-      if (result == pfile->spec_nodes.n__VA_OPT__)
-	maybe_va_opt_error (pfile);
-
-      /* For -Wc++-compat, warn about use of C++ named operators.  */
-      if (result->flags & NODE_WARN_OPERATOR)
-	cpp_warning (pfile, CPP_W_CXX_OPERATOR_NAMES,
-		     "identifier \"%s\" is a special operator name in C++",
-		     NODE_NAME (result));
-    }
+/* Struct to hold the return value of the scan_cur_identifier () helper
+   function below.  */
 
+struct scan_id_result
+{
+  cpp_hashnode *node;
+  normalize_state nst;
+
+  scan_id_result ()
+    : node (nullptr)
+  {
+    nst = INITIAL_NORMALIZE_STATE;
+  }
+
+  explicit operator bool () const { return node; }
+};
+
+/* Helper function to scan an entire identifier beginning at
+   pfile->buffer->cur, and possibly containing extended characters (UCNs
+   and/or UTF-8).  Returns the cpp_hashnode for the identifier on success, or
+   else nullptr, as well as a normalize_state so that normalization warnings
+   may be issued once the token lexing is complete.  */
+
+static scan_id_result
+scan_cur_identifier (cpp_reader *pfile)
+{
+  const auto buffer = pfile->buffer;
+  const auto begin = buffer->cur;
+  scan_id_result result;
+  if (ISIDST (*buffer->cur))
+    {
+      ++buffer->cur;
+      cpp_hashnode *ignore;
+      result.node = lex_identifier (pfile, begin, false, &result.nst, &ignore);
+    }
+  else if (forms_identifier_p (pfile, true, &result.nst))
+    {
+      /* buffer->cur has been moved already by the call
+	 to forms_identifier_p.  */
+      cpp_hashnode *ignore;
+      result.node = lex_identifier (pfile, begin, true, &result.nst, &ignore);
+    }
   return result;
 }
 
@@ -2365,6 +2386,24 @@ create_literal (cpp_reader *pfile, cpp_token *token, const uchar *base,
   token->val.str.text = cpp_alloc_token_string (pfile, base, len);
 }
 
+/* Like create_literal(), but construct it from two separate strings
+   which are concatenated.  LEN2 may be 0 if no second string is
+   required.  */
+static void
+create_literal2 (cpp_reader *pfile, cpp_token *token, const uchar *base1,
+		 unsigned int len1, const uchar *base2, unsigned int len2,
+		 enum cpp_ttype type)
+{
+  token->type = type;
+  token->val.str.len = len1 + len2;
+  uchar *const dest = _cpp_unaligned_alloc (pfile, len1 + len2 + 1);
+  memcpy (dest, base1, len1);
+  if (len2)
+    memcpy (dest+len1, base2, len2);
+  dest[len1 + len2] = 0;
+  token->val.str.text = dest;
+}
+
 const uchar *
 cpp_alloc_token_string (cpp_reader *pfile,
 			const unsigned char *ptr, unsigned len)
@@ -2403,6 +2442,11 @@ struct lit_accum {
       rpos = NULL;
     return c;
   }
+
+  void create_literal2 (cpp_reader *pfile, cpp_token *token,
+			const uchar *base1, unsigned int len1,
+			const uchar *base2, unsigned int len2,
+			enum cpp_ttype type);
 };
 
 /* Subroutine of lex_raw_string: Append LEN chars from BASE to the buffer
@@ -2445,45 +2489,59 @@ lit_accum::read_begin (cpp_reader *pfile)
   rpos = BUFF_FRONT (last);
 }
 
-/* Returns true if a macro has been defined.
-   This might not work if compile with -save-temps,
-   or preprocess separately from compilation.  */
+/* Helper function to check if a string format macro, say from inttypes.h, is
+   placed touching a string literal, in which case it could be parsed as a C++11
+   user-defined string literal thus breaking the program.  Return TRUE if the
+   UDL should be ignored for now and preserved for potential macro
+   expansion.  */
 
 static bool
-is_macro(cpp_reader *pfile, const uchar *base)
-{
-  const uchar *cur = base;
-  if (! ISIDST (*cur))
-    return false;
-  unsigned int hash = HT_HASHSTEP (0, *cur);
-  ++cur;
-  while (ISIDNUM (*cur))
-    {
-      hash = HT_HASHSTEP (hash, *cur);
-      ++cur;
-    }
-  hash = HT_HASHFINISH (hash, cur - base);
-
-  cpp_hashnode *result = CPP_HASHNODE (ht_lookup_with_hash (pfile->hash_table,
-					base, cur - base, hash, HT_NO_INSERT));
-
-  return result && cpp_macro_p (result);
-}
-
-/* Returns true if a literal suffix does not have the expected form
-   and is defined as a macro.  */
-
-static bool
-is_macro_not_literal_suffix(cpp_reader *pfile, const uchar *base)
+maybe_ignore_udl_macro_suffix (cpp_reader *pfile, location_t src_loc,
+			       const uchar *suffix_begin, cpp_hashnode *node)
 {
   /* User-defined literals outside of namespace std must start with a single
      underscore, so assume anything of that form really is a UDL suffix.
      We don't need to worry about UDLs defined inside namespace std because
      their names are reserved, so cannot be used as macro names in valid
      programs.  */
-  if (base[0] == '_' && base[1] != '_')
+  if ((suffix_begin[0] == '_' && suffix_begin[1] != '_')
+      || !cpp_macro_p (node))
     return false;
-  return is_macro (pfile, base);
+
+  /* Maybe raise a warning here; caller should arrange not to consume
+     the tokens.  */
+  if (CPP_OPTION (pfile, warn_literal_suffix) && !pfile->state.skipping)
+    cpp_warning_with_line (pfile, CPP_W_LITERAL_SUFFIX, src_loc, 0,
+			   "invalid suffix on literal; C++11 requires a space "
+			   "between literal and string macro");
+  return true;
+}
+
+/* Like create_literal2(), but also prepend all the accumulated data from
+   the lit_accum struct.  */
+void
+lit_accum::create_literal2 (cpp_reader *pfile, cpp_token *token,
+			    const uchar *base1, unsigned int len1,
+			    const uchar *base2, unsigned int len2,
+			    enum cpp_ttype type)
+{
+  const unsigned int tot_len = accum + len1 + len2;
+  uchar *dest = _cpp_unaligned_alloc (pfile, tot_len + 1);
+  token->type = type;
+  token->val.str.len = tot_len;
+  token->val.str.text = dest;
+  for (_cpp_buff *buf = first; buf; buf = buf->next)
+    {
+      size_t len = BUFF_FRONT (buf) - buf->base;
+      memcpy (dest, buf->base, len);
+      dest += len;
+    }
+  memcpy (dest, base1, len1);
+  dest += len1;
+  if (len2)
+    memcpy (dest, base2, len2);
+  dest += len2;
+  *dest = '\0';
 }
 
 /* Lexes a raw string.  The stored string contains the spelling,
@@ -2758,26 +2816,25 @@ lex_raw_string (cpp_reader *pfile, cpp_token *token, const uchar *base)
 
   if (CPP_OPTION (pfile, user_literals))
     {
-      /* If a string format macro, say from inttypes.h, is placed touching
-	 a string literal it could be parsed as a C++11 user-defined string
-	 literal thus breaking the program.  */
-      if (is_macro_not_literal_suffix (pfile, pos))
-	{
-	  /* Raise a warning, but do not consume subsequent tokens.  */
-	  if (CPP_OPTION (pfile, warn_literal_suffix) && !pfile->state.skipping)
-	    cpp_warning_with_line (pfile, CPP_W_LITERAL_SUFFIX,
-				   token->src_loc, 0,
-				   "invalid suffix on literal; C++11 requires "
-				   "a space between literal and string macro");
-	}
-      /* Grab user defined literal suffix.  */
-      else if (ISIDST (*pos))
-	{
-	  type = cpp_userdef_string_add_type (type);
-	  ++pos;
+      const uchar *const suffix_begin = pos;
+      pfile->buffer->cur = pos;
 
-	  while (ISIDNUM (*pos))
-	    ++pos;
+      if (const auto sr = scan_cur_identifier (pfile))
+	{
+	  if (maybe_ignore_udl_macro_suffix (pfile, token->src_loc,
+					     suffix_begin, sr.node))
+	      pfile->buffer->cur = suffix_begin;
+	  else
+	    {
+	      type = cpp_userdef_string_add_type (type);
+	      accum.create_literal2 (pfile, token, base, suffix_begin - base,
+				     NODE_NAME (sr.node), NODE_LEN (sr.node),
+				     type);
+	      if (accum.first)
+		_cpp_release_buff (pfile, accum.first);
+	      warn_about_normalization (pfile, token, &sr.nst, true);
+	      return;
+	    }
 	}
     }
 
@@ -2787,21 +2844,8 @@ lex_raw_string (cpp_reader *pfile, cpp_token *token, const uchar *base)
     create_literal (pfile, token, base, pos - base, type);
   else
     {
-      size_t extra_len = pos - base;
-      uchar *dest = _cpp_unaligned_alloc (pfile, accum.accum + extra_len + 1);
-
-      token->type = type;
-      token->val.str.len = accum.accum + extra_len;
-      token->val.str.text = dest;
-      for (_cpp_buff *buf = accum.first; buf; buf = buf->next)
-	{
-	  size_t len = BUFF_FRONT (buf) - buf->base;
-	  memcpy (dest, buf->base, len);
-	  dest += len;
-	}
+      accum.create_literal2 (pfile, token, base, pos - base, nullptr, 0, type);
       _cpp_release_buff (pfile, accum.first);
-      memcpy (dest, base, extra_len);
-      dest[extra_len] = '\0';
     }
 }
 
@@ -2908,39 +2952,40 @@ lex_string (cpp_reader *pfile, cpp_token *token, const uchar *base)
     cpp_error (pfile, CPP_DL_PEDWARN, "missing terminating %c character",
 	       (int) terminator);
 
+  pfile->buffer->cur = cur;
+  const uchar *const suffix_begin = cur;
+
   if (CPP_OPTION (pfile, user_literals))
     {
-      /* If a string format macro, say from inttypes.h, is placed touching
-	 a string literal it could be parsed as a C++11 user-defined string
-	 literal thus breaking the program.  */
-      if (is_macro_not_literal_suffix (pfile, cur))
-	{
-	  /* Raise a warning, but do not consume subsequent tokens.  */
-	  if (CPP_OPTION (pfile, warn_literal_suffix) && !pfile->state.skipping)
-	    cpp_warning_with_line (pfile, CPP_W_LITERAL_SUFFIX,
-				   token->src_loc, 0,
-				   "invalid suffix on literal; C++11 requires "
-				   "a space between literal and string macro");
-	}
-      /* Grab user defined literal suffix.  */
-      else if (ISIDST (*cur))
+      if (const auto sr = scan_cur_identifier (pfile))
 	{
-	  type = cpp_userdef_char_add_type (type);
-	  type = cpp_userdef_string_add_type (type);
-          ++cur;
-
-	  while (ISIDNUM (*cur))
-	    ++cur;
+	  if (maybe_ignore_udl_macro_suffix (pfile, token->src_loc,
+					     suffix_begin, sr.node))
+	    pfile->buffer->cur = suffix_begin;
+	  else
+	    {
+	      /* Grab user defined literal suffix.  */
+	      type = cpp_userdef_char_add_type (type);
+	      type = cpp_userdef_string_add_type (type);
+	      create_literal2 (pfile, token, base, suffix_begin - base,
+			       NODE_NAME (sr.node), NODE_LEN (sr.node), type);
+	      warn_about_normalization (pfile, token, &sr.nst, true);
+	      return;
+	    }
 	}
     }
   else if (CPP_OPTION (pfile, cpp_warn_cxx11_compat)
-	   && is_macro (pfile, cur)
 	   && !pfile->state.skipping)
-    cpp_warning_with_line (pfile, CPP_W_CXX11_COMPAT,
-			   token->src_loc, 0, "C++11 requires a space "
-			   "between string literal and macro");
+    {
+      const auto sr = scan_cur_identifier (pfile);
+      /* Maybe raise a warning, but do not consume the tokens.  */
+      pfile->buffer->cur = suffix_begin;
+      if (sr && cpp_macro_p (sr.node))
+	cpp_warning_with_line (pfile, CPP_W_CXX11_COMPAT,
+			       token->src_loc, 0, "C++11 requires a space "
+			       "between string literal and macro");
+    }
 
-  pfile->buffer->cur = cur;
   create_literal (pfile, token, base, cur - base, type);
 }
 
@@ -3915,9 +3960,10 @@ _cpp_lex_direct (cpp_reader *pfile)
       result->type = CPP_NAME;
       {
 	struct normalize_state nst = INITIAL_NORMALIZE_STATE;
-	result->val.node.node = lex_identifier (pfile, buffer->cur - 1, false,
-						&nst,
-						&result->val.node.spelling);
+	const auto node = lex_identifier (pfile, buffer->cur - 1, false, &nst,
+					  &result->val.node.spelling);
+	result->val.node.node = node;
+	identifier_diagnostics_on_lex (pfile, node);
 	warn_about_normalization (pfile, result, &nst, true);
       }
 
@@ -4220,8 +4266,10 @@ _cpp_lex_direct (cpp_reader *pfile)
 	if (forms_identifier_p (pfile, true, &nst))
 	  {
 	    result->type = CPP_NAME;
-	    result->val.node.node = lex_identifier (pfile, base, true, &nst,
-						    &result->val.node.spelling);
+	    const auto node = lex_identifier (pfile, base, true, &nst,
+					      &result->val.node.spelling);
+	    result->val.node.node = node;
+	    identifier_diagnostics_on_lex (pfile, node);
 	    warn_about_normalization (pfile, result, &nst, true);
 	    break;
 	  }
@@ -4353,7 +4401,7 @@ cpp_digraph2name (enum cpp_ttype type)
 }
 
 /* Write the spelling of an identifier IDENT, using UCNs, to BUFFER.
-   The buffer must already contain the enough space to hold the
+   The buffer must already contain enough space to hold the
    token's spelling.  Returns a pointer to the character after the
    last character written.  */
 unsigned char *
@@ -4375,7 +4423,7 @@ _cpp_spell_ident_ucns (unsigned char *buffer, cpp_hashnode *ident)
 }
 
 /* Write the spelling of a token TOKEN to BUFFER.  The buffer must
-   already contain the enough space to hold the token's spelling.
+   already contain enough space to hold the token's spelling.
    Returns a pointer to the character after the last character written.
    FORSTRING is true if this is to be the spelling after translation
    phase 1 (with the original spelling of extended identifiers), false