On Thu, Jan 11, 2018 at 02:06:06PM +0000, Joseph Myers wrote:
> On Thu, 11 Jan 2018, David Brown wrote:
>
> > Maybe it is easier to say "gcc supports <=> in C++2a, and as an
> > extension also supports it in C and C++ of any standard" ? I don't
> > believe there is any way for it to conflict with existing valid code, so
> > it would do no harm as a gcc extension like that - and C users can then
> > use it too.
>
> As per previous IRC discussion, changing the lexing to support this
> pp-token can break valid code in previous standards, e.g. code
> concatenating <=> and >, then stringizing the result (the C++ proposal for
> adding this feature also notes some obscure cases where the character
> sequence <=> can actually occur as tokens, not just pp-tokens -
> "X<&Y::operator<=>" and "x+&operator<=>y" - so of course patches adding
> this feature should add testcases using such cases with older -std=
> options).
>
> Changes to cpp_avoid_paste (so that preprocessed output does not put a
> pp-token starting with > immediately after <=) do not need to be
> conditional on the standard version, however.
Here is a patch that attempts to implement this (in libcpp + gcc/testsuite
only so far).
It needs to be parsed and handled in the C++ FE obviously, which is missing.
2018-08-30 Jakub Jelinek <ja...@redhat.com>
P0515R3 - Consistent comparison
* include/cpplib.h (TTYPE_TABLE): Add CPP_SPACESHIP.
(struct cpp_options): Add spaceship field.
* init.c (struct lang_flags): Add spaceship field.
(lang_defaults): Add spaceship column.
(cpp_set_lang): Initialize CPP_OPTION (pfile, spaceship).
* lex.c (_cpp_lex_direct): Lex CPP_SPACESHIP.
(cpp_avoid_paste): Avoid pasting <= with >.
* c-c++-common/cpp/spaceship-1.c: New test.
* g++.dg/cpp/spaceship-1.C: New test.
--- libcpp/include/cpplib.h.jj 2018-08-26 22:43:12.510939169 +0200
+++ libcpp/include/cpplib.h 2018-08-30 18:55:55.483035882 +0200
@@ -91,6 +91,7 @@ struct _cpp_file;
OP(XOR_EQ, "^=") \
OP(RSHIFT_EQ, ">>=")
\
OP(LSHIFT_EQ, "<<=")
\
+ OP(SPACESHIP, "<=>")
\
/* Digraphs together, beginning with CPP_FIRST_DIGRAPH. */ \
OP(HASH, "#") /* digraphs */ \
OP(PASTE, "##") \
@@ -480,6 +481,9 @@ struct cpp_options
/* Nonzero for C++2a __VA_OPT__ feature. */
unsigned char va_opt;
+ /* Nonzero for C++2a <=> operator. */
+ unsigned char spaceship;
+
/* Holds the name of the target (execution) character set. */
const char *narrow_charset;
--- libcpp/init.c.jj 2018-08-26 22:43:13.760918150 +0200
+++ libcpp/init.c 2018-08-30 18:57:41.479297007 +0200
@@ -92,30 +92,31 @@ struct lang_flags
char trigraphs;
char utf8_char_literals;
char va_opt;
+ char spaceship;
};
static const struct lang_flags lang_defaults[] =
-{ /* c99 c++ xnum xid c11 std digr ulit rlit udlit bincst digsep
trig u8chlit vaopt */
- /* GNUC89 */ { 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0,
0, 0, 1 },
- /* GNUC99 */ { 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1 },
- /* GNUC11 */ { 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1 },
- /* GNUC17 */ { 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1 },
- /* STDC89 */ { 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
1, 0, 0 },
- /* STDC94 */ { 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0 },
- /* STDC99 */ { 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0 },
- /* STDC11 */ { 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
1, 0, 0 },
- /* STDC17 */ { 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
1, 0, 0 },
- /* GNUCXX */ { 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0,
0, 0, 1 },
- /* CXX98 */ { 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0 },
- /* GNUCXX11 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0,
0, 0, 1 },
- /* CXX11 */ { 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
1, 0, 0 },
- /* GNUCXX14 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 0, 1 },
- /* CXX14 */ { 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 0, 0 },
- /* GNUCXX17 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 1, 1 },
- /* CXX17 */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 1, 0 },
- /* GNUCXX2A */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 1, 1 },
- /* CXX2A */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 1, 1 },
- /* ASM */ { 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0 }
+{ /* c99 c++ xnum xid c11 std digr ulit rlit udlit bincst digsep
trig u8chlit vaopt spaceship */
+ /* GNUC89 */ { 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0,
0, 0, 1, 0 },
+ /* GNUC99 */ { 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1, 0 },
+ /* GNUC11 */ { 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1, 0 },
+ /* GNUC17 */ { 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0,
0, 0, 1, 0 },
+ /* STDC89 */ { 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* STDC94 */ { 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* STDC99 */ { 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* STDC11 */ { 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* STDC17 */ { 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* GNUCXX */ { 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0,
0, 0, 1, 0 },
+ /* CXX98 */ { 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0,
1, 0, 0, 0 },
+ /* GNUCXX11 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0,
0, 0, 1, 0 },
+ /* CXX11 */ { 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0,
1, 0, 0, 0 },
+ /* GNUCXX14 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 0, 1, 0 },
+ /* CXX14 */ { 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 0, 0, 0 },
+ /* GNUCXX17 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 1, 1, 0 },
+ /* CXX17 */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 1, 0, 0 },
+ /* GNUCXX2A */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
0, 1, 1, 1 },
+ /* CXX2A */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 1, 1, 1 },
+ /* ASM */ { 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0 }
};
/* Sets internal flags correctly for a given language. */
@@ -141,6 +142,7 @@ cpp_set_lang (cpp_reader *pfile, enum c_
CPP_OPTION (pfile, trigraphs) = l->trigraphs;
CPP_OPTION (pfile, utf8_char_literals) = l->utf8_char_literals;
CPP_OPTION (pfile, va_opt) = l->va_opt;
+ CPP_OPTION (pfile, spaceship) = l->spaceship;
}
/* Initialize library global state. */
--- libcpp/lex.c.jj 2018-08-26 22:43:14.784900935 +0200
+++ libcpp/lex.c 2018-08-30 19:02:43.261340974 +0200
@@ -2963,7 +2963,11 @@ _cpp_lex_direct (cpp_reader *pfile)
result->type = CPP_LESS;
if (*buffer->cur == '=')
- buffer->cur++, result->type = CPP_LESS_EQ;
+ {
+ buffer->cur++, result->type = CPP_LESS_EQ;
+ if (*buffer->cur == '>' && CPP_OPTION (pfile, spaceship))
+ buffer->cur++, result->type = CPP_SPACESHIP;
+ }
else if (*buffer->cur == '<')
{
buffer->cur++;
@@ -3466,6 +3470,7 @@ cpp_avoid_paste (cpp_reader *pfile, cons
|| (CPP_OPTION (pfile, objc)
&& token1->val.str.text[0] == '@'
&& (b == CPP_NAME || b == CPP_STRING)));
+ case CPP_LESS_EQ: return c == '>';
case CPP_STRING:
case CPP_WSTRING:
case CPP_UTF8STRING:
--- gcc/testsuite/c-c++-common/cpp/spaceship-1.c.jj 2018-08-30
19:41:13.762257530 +0200
+++ gcc/testsuite/c-c++-common/cpp/spaceship-1.c 2018-08-30
19:49:09.338386388 +0200
@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-std=c11" { target c } } */
+
+#define A(x, y) x##y
+A(<=, >) /* { dg-error "does not give a valid preprocessing token" "" {
target { ! c++2a } } } */
+A(<=>, >) /* { dg-error "does not give a valid preprocessing token" "" {
target c++2a } } */
--- gcc/testsuite/g++.dg/cpp/spaceship-1.C.jj 2018-08-30 19:58:56.152695104
+0200
+++ gcc/testsuite/g++.dg/cpp/spaceship-1.C 2018-08-30 19:59:20.802288063
+0200
@@ -0,0 +1,8 @@
+// { dg-do compile { target c++17_down } }
+// { dg-options "-Wno-pointer-arith" }
+
+struct X {};
+bool operator<= (X, X);
+template<bool (X, X)> struct Y {};
+Y<&operator<=> y;
+bool foo (bool (*fn) (X, X), int n) { return n+&operator<=> fn; }
Jakub
