PR c++/52538 Extend C++11 UDLs to be compatible with inttypes.h macros

[Ollie Wild, 2012-04-23 03:59:14]

Add new option, -Wreserved-user-defined-literal.

This option, which is enabled by default, causes the preprocessor to warn
when a string or character literal is followed by a ud-suffix which does
not begin with an underscore.  According to [lex.ext]p10, this is
ill-formed.

Also modifies the preprocessor to treat such ill-formed suffixes as separate
preprocessing tokens.  This is consistent with the Clang front end (see
http://llvm.org/viewvc/llvm-project?view=rev&revision=152287), and enables
backwards compatibility with code that uses formatting macros from
<inttypes.h>, as in the following code block:

  int main() {
    int64_t i64 = 123;
    printf("My int64: %"PRId64"\n", i64);
  }

Tested via bootstrap + test.

Okay for trunk?

Thanks,
Ollie


2012-04-22   Ollie Wild  <aaw@google.com>

	* gcc/c-family/c-common.c:
	* gcc/c-family/c-opts.c (c_common_handle_option):
	* gcc/c-family/c.opt:
	* gcc/doc/invoke.texi (struct A):
	* gcc/testsuite/g++.dg/cpp0x/Wreserved-user-defined-literal.C (test):
	(main):
	* libcpp/include/cpplib.h (struct cpp_options):
	* libcpp/init.c (cpp_create_reader):
	* libcpp/lex.c (lex_raw_string):
	(lex_string):

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 4eacd19..f79020c 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -8820,6 +8820,7 @@ static const struct reason_option_codes_t option_codes[] =
{
   {CPP_W_NORMALIZE,			OPT_Wnormalized_},
   {CPP_W_INVALID_PCH,			OPT_Winvalid_pch},
   {CPP_W_WARNING_DIRECTIVE,		OPT_Wcpp},
+  {CPP_W_RESERVED_USER_LITERALS,	OPT_Wreserved_user_defined_literal},
   {CPP_W_NONE,				0}
 };
 
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index 17e1958..a812762 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -510,6 +510,10 @@ c_common_handle_option (size_t scode, const char *arg, int
value,
 	  break;
 	}
 
+    case OPT_Wreserved_user_defined_literal:
+      cpp_opts->warn_reserved_user_literals = value;
+      break;
+
     case OPT_Wreturn_type:
       warn_return_type = value;
       break;
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index d8c944d..c8a0c84 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -593,6 +593,10 @@ Wreorder
 C++ ObjC++ Var(warn_reorder) Warning
 Warn when the compiler reorders code
 
+Wreserved-user-defined-literal
+C++ ObjC++ Warning
+Warn when a string or character literal is followed by a ud-suffix which does
not begin with an underscore.
+
 Wreturn-type
 C ObjC C++ ObjC++ Var(warn_return_type) Warning
 Warn whenever a function's return type defaults to \"int\" (C), or about
inconsistent return types (C++)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8ca2f4e..ddf0fc6 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -199,7 +199,7 @@ in the following sections.
 -fvisibility-ms-compat @gol
 -Wabi  -Wconversion-null  -Wctor-dtor-privacy @gol
 -Wdelete-non-virtual-dtor -Wnarrowing -Wnoexcept @gol
--Wnon-virtual-dtor  -Wreorder @gol
+-Wnon-virtual-dtor  -Wreorder -Wreserved-user-defined-literal @gol
 -Weffc++  -Wstrict-null-sentinel @gol
 -Wno-non-template-friend  -Wold-style-cast @gol
 -Woverloaded-virtual  -Wno-pmf-conversions @gol
@@ -2478,6 +2478,30 @@ struct A @{
 The compiler rearranges the member initializers for @samp{i}
 and @samp{j} to match the declaration order of the members, emitting
 a warning to that effect.  This warning is enabled by @option{-Wall}.
+
+@item -Wreserved-user-defined-literal @r{(C++ and Objective-C++ only)}
+@opindex Wreserved-user-defined-literal
+@opindex Wno-reserved-user-defined-literal
+Warn when a string or character literal is followed by a ud-suffix which does
+not begin with an underscore.  As a conforming extension, GCC treats such
+suffixes as separate preprocessing tokens in order to maintain backwards
+compatibility with code that uses formatting macros from @code{<inttypes.h>}.
+For example:
+
+@smallexample
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+#include <stdio.h>
+
+int main() @{
+  int64_t i64 = 123;
+  printf("My int64: %"PRId64"\n", i64);
+@}
+@end smallexample
+
+In this case, @code{PRId64} is treated as a separate preprocessing token.
+
+This warning is enabled by default.
 @end table
 
 The following @option{-W@dots{}} options are not affected by @option{-Wall}.
diff --git a/gcc/testsuite/g++.dg/cpp0x/Wreserved-user-defined-literal.C
b/gcc/testsuite/g++.dg/cpp0x/Wreserved-user-defined-literal.C
new file mode 100644
index 0000000..66de5c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/Wreserved-user-defined-literal.C
@@ -0,0 +1,29 @@
+// { dg-do run }
+// { dg-options "-std=c++0x" }
+
+// Make sure -Wreserved-user-defined-literal is enabled by default and
+// triggers as expected.
+
+#define BAR "bar"
+#define PLUS_ONE + 1
+
+#include <cstdint>
+#include <cassert>
+
+
+void
+test()
+{
+  char c = '3'PLUS_ONE;	  // { dg-warning "invalid suffix on literal" }
+  char s[] = "foo"BAR;	  // { dg-warning "invalid suffix on literal" }
+
+  assert(c == '4');
+  assert(s[3] != '\0');
+  assert(s[3] == 'b');
+}
+
+int
+main()
+{
+  test();
+}
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index bf59d01..84cacb0 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -427,6 +427,10 @@ struct cpp_options
   /* Nonzero for C++ 2011 Standard user-defnied literals.  */
   unsigned char user_literals;
 
+  /* Nonzero means warn when a string or character literal is followed by a
+     ud-suffix which does not beging with an underscore.  */
+  unsigned char warn_reserved_user_literals;
+
   /* Holds the name of the target (execution) character set.  */
   const char *narrow_charset;
 
@@ -906,7 +910,8 @@ enum {
   CPP_W_CXX_OPERATOR_NAMES,
   CPP_W_NORMALIZE,
   CPP_W_INVALID_PCH,
-  CPP_W_WARNING_DIRECTIVE
+  CPP_W_WARNING_DIRECTIVE,
+  CPP_W_RESERVED_USER_LITERALS
 };
 
 /* Output a diagnostic of some kind.  */
diff --git a/libcpp/init.c b/libcpp/init.c
index 5fa82ca..2688699 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -175,6 +175,7 @@ cpp_create_reader (enum c_lang lang, hash_table *table,
   CPP_OPTION (pfile, warn_variadic_macros) = 1;
   CPP_OPTION (pfile, warn_builtin_macro_redefined) = 1;
   CPP_OPTION (pfile, warn_normalize) = normalized_C;
+  CPP_OPTION (pfile, warn_reserved_user_literals) = 1;
 
   /* Default CPP arithmetic to something sensible for the host for the
      benefit of dumb users like fix-header.  */
diff --git a/libcpp/lex.c b/libcpp/lex.c
index 9d23002..3589a81 100644
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -1553,14 +1553,30 @@ lex_raw_string (cpp_reader *pfile, cpp_token *token,
const uchar *base,
 
   if (CPP_OPTION (pfile, user_literals))
     {
+      /* According to C++11 [lex.ext]p10, a ud-suffix not starting with an
+	 underscore is ill-formed.  Since this breaks programs using macros
+	 from inttypes.h, we generate a warning and treat the ud-suffix as a
+	 separate preprocessing token.  This approach is under discussion by
+	 the standards committee, and has been adopted as a conforming
+	 extension by other front ends such as clang. */
+      if (ISALPHA(*cur))
+	{
+	  // Raise a warning, but do not consume subsequent tokens.
+	  if (CPP_OPTION (pfile, warn_reserved_user_literals))
+	    cpp_warning_with_line (pfile, CPP_W_RESERVED_USER_LITERALS,
+				   token->src_loc, 0,
+				   "invalid suffix on literal; C++11 requires "
+				   "a space between literal and identifier");
+	}
       /* Grab user defined literal suffix.  */
-      if (ISIDST (*cur))
+      else if (*cur == '_')
 	{
 	  type = cpp_userdef_string_add_type (type);
 	  ++cur;
+
+	  while (ISIDNUM (*cur))
+	    ++cur;
 	}
-      while (ISIDNUM (*cur))
-	++cur;
     }
 
   pfile->buffer->cur = cur;
@@ -1668,15 +1684,31 @@ lex_string (cpp_reader *pfile, cpp_token *token, const
uchar *base)
 
   if (CPP_OPTION (pfile, user_literals))
     {
+      /* According to C++11 [lex.ext]p10, a ud-suffix not starting with an
+	 underscore is ill-formed.  Since this breaks programs using macros
+	 from inttypes.h, we generate a warning and treat the ud-suffix as a
+	 separate preprocessing token.  This approach is under discussion by
+	 the standards committee, and has been adopted as a conforming
+	 extension by other front ends such as clang. */
+      if (ISALPHA(*cur))
+	{
+	  // Raise a warning, but do not consume subsequent tokens.
+	  if (CPP_OPTION (pfile, warn_reserved_user_literals))
+	    cpp_warning_with_line (pfile, CPP_W_RESERVED_USER_LITERALS,
+				   token->src_loc, 0,
+				   "invalid suffix on literal; C++11 requires "
+				   "a space between literal and identifier");
+	}
       /* Grab user defined literal suffix.  */
-      if (ISIDST (*cur))
+      else if (*cur == '_')
 	{
 	  type = cpp_userdef_char_add_type (type);
 	  type = cpp_userdef_string_add_type (type);
           ++cur;
+
+	  while (ISIDNUM (*cur))
+	    ++cur;
 	}
-      while (ISIDNUM (*cur))
-	++cur;
     }
 
   pfile->buffer->cur = cur;

--
This patch is available for review at http://codereview.appspot.com/6109043

[tromey_redhat.com, 2012-04-26 13:35:33]

>>>>> "Ollie" == Ollie Wild <aaw@google.com> writes:

Ollie> 2012-04-22   Ollie Wild  <aaw@google.com>
Ollie> 	* gcc/c-family/c-common.c:
Ollie> 	* gcc/c-family/c-opts.c (c_common_handle_option):
Ollie> 	* gcc/c-family/c.opt:
Ollie> 	* gcc/doc/invoke.texi (struct A):
Ollie> 	* gcc/testsuite/g++.dg/cpp0x/Wreserved-user-defined-literal.C (test):
Ollie> 	(main):
Ollie> 	* libcpp/include/cpplib.h (struct cpp_options):
Ollie> 	* libcpp/init.c (cpp_create_reader):
Ollie> 	* libcpp/lex.c (lex_raw_string):
Ollie> 	(lex_string):

One little nit.

Ollie> +      if (ISALPHA(*cur))

Space before open paren.

Ollie> +      if (ISALPHA(*cur))

And here.

This is ok with this change.

thanks,
Tom

[Ollie Wild, 2012-04-27 14:30:50]

On Thu, Apr 26, 2012 at 8:35 AM, Tom Tromey <tromey@redhat.com> wrote:
>
> This is ok with this change.

Thanks.  Updated and submitted to trunk.

Ollie