On Mon, Aug 15, 2022 at 05:48:34PM +0000, Joseph Myers wrote:
> On Sat, 13 Aug 2022, Marek Polacek via Gcc-patches wrote:
>
> > This patch also defines nullptr_t in <stddef.h>. I'm uncertain about
> > the __STDC_VERSION__ version I should be checking. Also, I'm not
>
> We're using defined (__STDC_VERSION__) && __STDC_VERSION__ > 201710L until
> the final version for C23 is settled.
OK, adjusted.
> > defining __STDC_VERSION_STDDEF_H__ yet, because I don't know what value
> > it should be defined to. Do we know yet?
>
> No, and Jens's comments on the editorial review before CD ballot include
> that lots of headers don't yet have such a macro definition but should
> have one, as well as needing consistency for the numbers.
>
> We won't know the final values for these macros until much later, because
> the timescale depends on whether ISO decides to delay things at any point
> by coming up with a long list of editorial issues required to follow the
> JTC1 Directives as they did for C17 (objections to particular words
> appearing in non-normative text, etc.).
Ack, thanks.
> > - { "nullptr", RID_NULLPTR, D_CXXONLY | D_CXX11 | D_CXXWARN },
> > + { "nullptr", RID_NULLPTR, D_CXX11 | D_CXXWARN },
>
> You need to use D_C2X (which doesn't yet exist). In pre-C23 modes,
> nullptr needs to be a normal identifier that can be used in all contexts
> where identifiers can be used, not a keyword at all (and then you need a
> c11-nullptr*.c test to verify that use of it as an identifier works as
> expected).
Fixed. Adding D_C2X meant that I had to enlarge struct c_common_resword
by a word.
> > diff --git a/gcc/c/c-convert.cc b/gcc/c/c-convert.cc
> > index 18083d59618..013fe6b2a53 100644
> > --- a/gcc/c/c-convert.cc
> > +++ b/gcc/c/c-convert.cc
> > @@ -133,6 +133,14 @@ c_convert (tree type, tree expr, bool init_const)
> > (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
> >
> > case POINTER_TYPE:
> > + /* The type nullptr_t may be converted to a pointer type. The result is
> > + a null pointer value. */
> > + if (NULLPTR_TYPE_P (TREE_TYPE (e)))
> > + {
> > + ret = build_int_cst (type, 0);
> > + goto maybe_fold;
> > + }
>
> That looks like it would lose side-effects. You need to preserve
> side-effects in an expression of nullptr_t type being converted to a
> pointer type, and need an execution testcase that verifies such
> side-effects are preserved.
Ah, of course. Fixed by building up a COMPOUND_EXPR. Covered by
c2x-nullptr-5.c.
> Also, you need to make sure that (void *)nullptr is not treated as a null
> pointer constant, only a null pointer; build_int_cst (type, 0) would
> produce a null pointer constant when type is void *. (void *)nullptr
> should be handled similarly to (void *)(void *)0, which isn't a null
> pointer constant either.
That (void *)nullptr is not considered an NPC ought to be achieved by
build_c_cast wrapping the result of c_convert in a NOP_EXPR:
/* Don't allow the results of casting to floating-point or complex
types be confused with actual constants, or casts involving
integer and pointer types other than direct integer-to-integer
and integer-to-pointer be confused with integer constant
expressions and null pointer constants. */
Then null_pointer_constant_p sees the NOP_EXPR and returns false. I've
added a comment explaining that.
> > @@ -133,6 +133,13 @@ null_pointer_constant_p (const_tree expr)
> > /* This should really operate on c_expr structures, but they aren't
> > yet available everywhere required. */
> > tree type = TREE_TYPE (expr);
> > +
> > + /* An integer constant expression with the value 0, such an expression
> > + cast to type void*, or the predefined constant nullptr, are a null
> > + pointer constant. */
> > + if (NULLPTR_TYPE_P (type))
> > + return true;
>
> That looks wrong. You need to distinguish null pointer constants of type
> nullptr_t (nullptr, possibly enclosed in parentheses, possibly the
> selected alternative from _Generic) from all other expressions of type
> nullptr_t (including (nullptr_t)nullptr, which isn't a null pointer
> constant any more than (void *)(void *)0).
Ah, okay. I had just copied what we do in C++ in null_ptr_cst_p and the
rest of the patch worked under that assumption. I've added some tests
for this too. Except I don't really understand the _Generic comment so
I only have tests for _Generic that were in the previous version.
Changing null_pointer_constant_p mean that I had to adjust
build_binary_op/EQ_EXPR.
> Then, for each context where it matters whether a nullptr_t value is a
> null pointer constant, there need to be testcases that the two cases are
> properly distinguished. This includes at least equality comparisons with
> a pointer that is not a null pointer constant (seem only to be allowed
> with nullptr, not with other nullptr_t expressions). (I think for
> conditional expressions, conditionals between nullptr_t and an integer
> null pointer constant are always invalid, whether or not the nullptr_t is
> a null pointer constant, while conditionals between nullptr_t and a
> pointer are always valid.)
I see, it's because 6.5.9 says that if one of the operands of == or !=
has type nullptr_t but the other one doesn't, the other operand has to
be an NPC, not just a null pointer.
This should be tested in c2x-nullptr-1.c:test2 and c2x-nullptr-3.c:test1.
For instance, "p == (nullptr_t)nullptr", where p is a pointer, does not
compile.
> > +/* The type nullptr_t shall not be converted to any type other than bool or
> > + a pointer type. No type other than nullptr_t shall be converted to nullptr_t. */
>
> That's other than *void*, bool or a pointer type. (That's a correct fix
> to the N3042 wording in N3047. There are other problems in the
> integration of nullptr in N3047 that are only fixed in my subsequent fixes
> as part of the editorial review - and many issues with integration of
> other papers that haven't yet been fixed, I currently have 25 open merge
> requests resulting from editorial review.) And of course conversions from
> nullptr_t to void should be tested.
Thanks, tests added to c2x-nullptr-1.c:test1. I notice that 6.3.2.4 still
says "The type nullptr_t may be converted to bool or to a pointer type";
isn't it missing the ", void" here too?
> > diff --git a/gcc/testsuite/gcc.dg/c2x-nullptr-4.c b/gcc/testsuite/gcc.dg/c2x-nullptr-4.c
> > new file mode 100644
> > index 00000000000..5b15e75d159
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/c2x-nullptr-4.c
> > @@ -0,0 +1,10 @@
> > +/* Test that we warn about `nullptr' pre-C2X. */
> > +/* { dg-do compile } */
> > +/* { dg-options "-std=c17 -pedantic-errors" } */
>
> This test is wrong - it's a normal identifier pre-C2x - but tests for
> previous standard versions shouldn't be called c2x-* in any case.
I see. I've removed this test and instead added c17-nullptr-2.c.
Thank you for the careful review.
Bootstrap/regtest running on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
This patch implements the C23 nullptr literal:
<https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3042.htm> (with
wording fixes from N3047), which is intended to replace the problematic
definition of NULL which might be either of integer type or void*.
Since C++ has had nullptr for over a decade now, it was relatively easy
to just move the built-in node definitions from the C++ FE to the C/C++
common code. Also, our DWARF emitter already handles NULLPTR_TYPE by
emitting DW_TAG_unspecified_type. However, I had to handle a lot of
contexts such as ?:, comparison, conversion, etc.
There are some minor differences, e.g. in C you can do
bool b = nullptr;
but in C++ you have to use direct-initialization:
bool b{nullptr};
And I think that
nullptr_t n = 0;
is only valid in C++.
Of course, C doesn't have to handle mangling, RTTI, substitution,
overloading, ...
This patch also defines nullptr_t in <stddef.h>. However, it does not
define __STDC_VERSION_STDDEF_H__ yet, because we don't know yet what value
it should be defined to.
gcc/c-family/ChangeLog:
* c-common.cc (c_common_reswords): Enable nullptr in C2X.
(c_common_nodes_and_builtins): Create the built-in node for nullptr.
* c-common.h (enum c_tree_index): Add CTI_NULLPTR, CTI_NULLPTR_TYPE.
(struct c_common_resword): Resize the disable member.
(D_C2X): Add.
(nullptr_node): Define.
(nullptr_type_node): Define.
(NULLPTR_TYPE_P): Define.
* c-pretty-print.cc (c_pretty_printer::simple_type_specifier): Handle
NULLPTR_TYPE.
(c_pretty_printer::direct_abstract_declarator): Likewise.
(c_pretty_printer::constant): Likewise.
gcc/c/ChangeLog:
* c-convert.cc (c_convert) <case POINTER_TYPE>: Handle NULLPTR_TYPE.
Give a better diagnostic when converting to nullptr_t.
* c-decl.cc (c_init_decl_processing): Perform C-specific nullptr
initialization.
* c-parser.cc (c_parse_init): Maybe OR D_C2X into mask.
(c_parser_postfix_expression): Handle RID_NULLPTR.
* c-typeck.cc (null_pointer_constant_p): Return true when expr is
nullptr_node.
(build_unary_op) <case TRUTH_NOT_EXPR>: Handle NULLPTR_TYPE.
(build_conditional_expr): Handle the case when the second/third operand
is NULLPTR_TYPE and third/second operand is POINTER_TYPE.
(convert_for_assignment): Handle converting an expression of type
nullptr_t to pointer/bool.
(build_binary_op) <case TRUTH_XOR_EXPR>: Handle NULLPTR_TYPE.
<case EQ_EXPR>: Handle comparing operands of type nullptr_t.
gcc/cp/ChangeLog:
* cp-tree.h (enum cp_tree_index): Remove CTI_NULLPTR, CTI_NULLPTR_TYPE.
Move it to c_tree_index.
(nullptr_node): No longer define here.
(nullptr_type_node): Likewise.
(NULLPTR_TYPE_P): Likewise.
* decl.cc (cxx_init_decl_processing): Only keep C++-specific nullptr
initialization; move the shared code to c_common_nodes_and_builtins.
gcc/ChangeLog:
* ginclude/stddef.h: Define nullptr_t.
gcc/testsuite/ChangeLog:
* gcc.dg/c11-nullptr-1.c: New test.
* gcc.dg/c17-nullptr-1.c: New test.
* gcc.dg/c17-nullptr-2.c: New test.
* gcc.dg/c2x-nullptr-1.c: New test.
* gcc.dg/c2x-nullptr-2.c: New test.
* gcc.dg/c2x-nullptr-3.c: New test.
* gcc.dg/c2x-nullptr-4.c: New test.
* gcc.dg/c2x-nullptr-5.c: New test.
---
gcc/c-family/c-common.cc | 20 ++-
gcc/c-family/c-common.h | 37 ++--
gcc/c-family/c-pretty-print.cc | 7 +
gcc/c/c-convert.cc | 25 ++-
gcc/c/c-decl.cc | 6 +
gcc/c/c-parser.cc | 10 ++
gcc/c/c-typeck.cc | 57 +++++-
gcc/cp/cp-tree.h | 8 -
gcc/cp/decl.cc | 8 +-
gcc/ginclude/stddef.h | 8 +
gcc/testsuite/gcc.dg/c11-nullptr-1.c | 10 ++
gcc/testsuite/gcc.dg/c17-nullptr-1.c | 10 ++
gcc/testsuite/gcc.dg/c17-nullptr-2.c | 10 ++
gcc/testsuite/gcc.dg/c2x-nullptr-1.c | 259 +++++++++++++++++++++++++++
gcc/testsuite/gcc.dg/c2x-nullptr-2.c | 9 +
gcc/testsuite/gcc.dg/c2x-nullptr-3.c | 78 ++++++++
gcc/testsuite/gcc.dg/c2x-nullptr-4.c | 11 ++
gcc/testsuite/gcc.dg/c2x-nullptr-5.c | 14 ++
18 files changed, 545 insertions(+), 42 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/c11-nullptr-1.c
create mode 100644 gcc/testsuite/gcc.dg/c17-nullptr-1.c
create mode 100644 gcc/testsuite/gcc.dg/c17-nullptr-2.c
create mode 100644 gcc/testsuite/gcc.dg/c2x-nullptr-1.c
create mode 100644 gcc/testsuite/gcc.dg/c2x-nullptr-2.c
create mode 100644 gcc/testsuite/gcc.dg/c2x-nullptr-3.c
create mode 100644 gcc/testsuite/gcc.dg/c2x-nullptr-4.c
create mode 100644 gcc/testsuite/gcc.dg/c2x-nullptr-5.c
base-commit: 530f80451a9e76896a0294e0f4bd59baff1ac27f
@@ -324,8 +324,10 @@ static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
if they match the mask.
Masks for languages:
- C --std=c89: D_C99 | D_CXXONLY | D_OBJC | D_CXX_OBJC
- C --std=c99: D_CXXONLY | D_OBJC
+ C --std=c89: D_C99 | D_C2X | D_CXXONLY | D_OBJC | D_CXX_OBJC
+ C --std=c99: D_C2X | D_CXXONLY | D_OBJC
+ C --std=c17: D_C2X | D_CXXONLY | D_OBJC
+ C --std=c2x: D_CXXONLY | D_OBJC
ObjC is like C except that D_OBJC and D_CXX_OBJC are not set
C++ --std=c++98: D_CONLY | D_CXX11 | D_CXX20 | D_OBJC
C++ --std=c++11: D_CONLY | D_CXX20 | D_OBJC
@@ -500,7 +502,7 @@ const struct c_common_resword c_common_reswords[] =
{ "namespace", RID_NAMESPACE, D_CXXONLY | D_CXXWARN },
{ "new", RID_NEW, D_CXXONLY | D_CXXWARN },
{ "noexcept", RID_NOEXCEPT, D_CXXONLY | D_CXX11 | D_CXXWARN },
- { "nullptr", RID_NULLPTR, D_CXXONLY | D_CXX11 | D_CXXWARN },
+ { "nullptr", RID_NULLPTR, D_C2X | D_CXX11 | D_CXXWARN },
{ "operator", RID_OPERATOR, D_CXXONLY | D_CXXWARN },
{ "private", RID_PRIVATE, D_CXX_OBJC | D_CXXWARN },
{ "protected", RID_PROTECTED, D_CXX_OBJC | D_CXXWARN },
@@ -4723,6 +4725,18 @@ c_common_nodes_and_builtins (void)
null_node = make_int_cst (1, 1);
TREE_TYPE (null_node) = c_common_type_for_size (POINTER_SIZE, 0);
+ /* Create the built-in nullptr node. This part of its initialization is
+ common to C and C++. The front ends can further adjust its definition
+ in {c,cxx}_init_decl_processing. In particular, we aren't setting the
+ alignment here for C++ backward ABI bug compatibility. */
+ nullptr_type_node = make_node (NULLPTR_TYPE);
+ TYPE_SIZE (nullptr_type_node) = bitsize_int (GET_MODE_BITSIZE (ptr_mode));
+ TYPE_SIZE_UNIT (nullptr_type_node) = size_int (GET_MODE_SIZE (ptr_mode));
+ TYPE_UNSIGNED (nullptr_type_node) = 1;
+ TYPE_PRECISION (nullptr_type_node) = GET_MODE_BITSIZE (ptr_mode);
+ SET_TYPE_MODE (nullptr_type_node, ptr_mode);
+ nullptr_node = build_int_cst (nullptr_type_node, 0);
+
/* Since builtin_types isn't gc'ed, don't export these nodes. */
memset (builtin_types, 0, sizeof (builtin_types));
}
@@ -375,6 +375,8 @@ enum c_tree_index
CTI_DEFAULT_FUNCTION_TYPE,
CTI_NULL,
+ CTI_NULLPTR,
+ CTI_NULLPTR_TYPE,
/* These are not types, but we have to look them up all the time. */
CTI_FUNCTION_NAME_DECL,
@@ -409,7 +411,7 @@ struct c_common_resword
{
const char *const word;
ENUM_BITFIELD(rid) const rid : 16;
- const unsigned int disable : 16;
+ const unsigned int disable : 32;
};
/* Mode used to build pointers (VOIDmode means ptr_mode). */
@@ -447,19 +449,20 @@ extern machine_mode c_default_pointer_mode;
#define D_CONLY 0x0001 /* C only (not in C++). */
#define D_CXXONLY 0x0002 /* C++ only (not in C). */
#define D_C99 0x0004 /* In C, C99 only. */
-#define D_CXX11 0x0008 /* In C++, C++11 only. */
-#define D_EXT 0x0010 /* GCC extension. */
-#define D_EXT89 0x0020 /* GCC extension incorporated in C99. */
-#define D_ASM 0x0040 /* Disabled by -fno-asm. */
-#define D_OBJC 0x0080 /* In Objective C and neither C nor C++. */
-#define D_CXX_OBJC 0x0100 /* In Objective C, and C++, but not C. */
-#define D_CXXWARN 0x0200 /* In C warn with -Wcxx-compat. */
-#define D_CXX_CONCEPTS 0x0400 /* In C++, only with concepts. */
-#define D_TRANSMEM 0X0800 /* C++ transactional memory TS. */
-#define D_CXX_CHAR8_T 0X1000 /* In C++, only with -fchar8_t. */
-#define D_CXX20 0x2000 /* In C++, C++20 only. */
-#define D_CXX_COROUTINES 0x4000 /* In C++, only with coroutines. */
-#define D_CXX_MODULES 0x8000 /* In C++, only with modules. */
+#define D_C2X 0x0008 /* In C, C2X only. */
+#define D_CXX11 0x0010 /* In C++, C++11 only. */
+#define D_EXT 0x0020 /* GCC extension. */
+#define D_EXT89 0x0040 /* GCC extension incorporated in C99. */
+#define D_ASM 0x0080 /* Disabled by -fno-asm. */
+#define D_OBJC 0x0100 /* In Objective C and neither C nor C++. */
+#define D_CXX_OBJC 0x0200 /* In Objective C, and C++, but not C. */
+#define D_CXXWARN 0x0400 /* In C warn with -Wcxx-compat. */
+#define D_CXX_CONCEPTS 0x0800 /* In C++, only with concepts. */
+#define D_TRANSMEM 0x1000 /* C++ transactional memory TS. */
+#define D_CXX_CHAR8_T 0x2000 /* In C++, only with -fchar8_t. */
+#define D_CXX20 0x4000 /* In C++, C++20 only. */
+#define D_CXX_COROUTINES 0x8000 /* In C++, only with coroutines. */
+#define D_CXX_MODULES 0x10000 /* In C++, only with modules. */
#define D_CXX_CONCEPTS_FLAGS D_CXXONLY | D_CXX_CONCEPTS
#define D_CXX_CHAR8_T_FLAGS D_CXXONLY | D_CXX_CHAR8_T
@@ -534,6 +537,9 @@ extern const unsigned int num_c_common_reswords;
/* The node for C++ `__null'. */
#define null_node c_global_trees[CTI_NULL]
+/* The nodes for `nullptr'. */
+#define nullptr_node c_global_trees[CTI_NULLPTR]
+#define nullptr_type_node c_global_trees[CTI_NULLPTR_TYPE]
extern GTY(()) tree c_global_trees[CTI_MAX];
@@ -1009,6 +1015,9 @@ extern void c_parse_final_cleanups (void);
#define DECL_UNNAMED_BIT_FIELD(NODE) \
(DECL_C_BIT_FIELD (NODE) && !DECL_NAME (NODE))
+/* True iff TYPE is cv decltype(nullptr). */
+#define NULLPTR_TYPE_P(TYPE) (TREE_CODE (TYPE) == NULLPTR_TYPE)
+
extern tree do_case (location_t, tree, tree);
extern tree build_stmt (location_t, enum tree_code, ...);
extern tree build_real_imag_expr (location_t, enum tree_code, tree);
@@ -321,6 +321,7 @@ pp_c_pointer (c_pretty_printer *pp, tree t)
_Bool -- C99
_Complex -- C99
_Imaginary -- C99
+ nullptr_t -- C23
struct-or-union-specifier
enum-specifier
typedef-name.
@@ -424,6 +425,9 @@ c_pretty_printer::simple_type_specifier (tree t)
else
translate_string ("<anonymous>");
break;
+ case NULLPTR_TYPE:
+ pp_c_ws_string (this, "nullptr_t");
+ break;
default:
pp_unsupported_tree (this, t);
@@ -678,6 +682,7 @@ c_pretty_printer::direct_abstract_declarator (tree t)
case COMPLEX_TYPE:
case TYPE_DECL:
case ERROR_MARK:
+ case NULLPTR_TYPE:
break;
default:
@@ -1219,6 +1224,8 @@ c_pretty_printer::constant (tree e)
pp_c_character_constant (this, e);
else if (TREE_CODE (type) == ENUMERAL_TYPE)
pp_c_enumeration_constant (this, e);
+ else if (NULLPTR_TYPE_P (type))
+ pp_string (this, "nullptr");
else
pp_c_integer_constant (this, e);
}
@@ -133,6 +133,20 @@ c_convert (tree type, tree expr, bool init_const)
(loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
case POINTER_TYPE:
+ /* The type nullptr_t may be converted to a pointer type. The result is
+ a null pointer value. */
+ if (NULLPTR_TYPE_P (TREE_TYPE (e)))
+ {
+ /* To make sure that (void *)nullptr is not a null pointer constant,
+ build_c_cast will create an additional NOP_EXPR around the result
+ of this conversion. */
+ if (TREE_SIDE_EFFECTS (e))
+ ret = build2 (COMPOUND_EXPR, type, e, build_int_cst (type, 0));
+ else
+ ret = build_int_cst (type, 0);
+ goto maybe_fold;
+ }
+ gcc_fallthrough ();
case REFERENCE_TYPE:
ret = convert_to_pointer (type, e);
goto maybe_fold;
@@ -180,7 +194,16 @@ c_convert (tree type, tree expr, bool init_const)
return ret;
}
- error ("conversion to non-scalar type requested");
+ /* If we are converting to nullptr_t, don't say "non-scalar type" because
+ the nullptr_t type is a scalar type. Only nullptr_t shall be converted
+ to nullptr_t. */
+ if (code == NULLPTR_TYPE)
+ {
+ error ("conversion from %qT to %qT", TREE_TYPE (e), type);
+ inform (input_location, "only %qT can be converted to %qT", type, type);
+ }
+ else
+ error ("conversion to non-scalar type requested");
return error_mark_node;
}
@@ -4531,6 +4531,12 @@ c_init_decl_processing (void)
pushdecl (build_decl (UNKNOWN_LOCATION, TYPE_DECL, get_identifier ("_Bool"),
boolean_type_node));
+ /* C-specific nullptr initialization. */
+ record_builtin_type (RID_MAX, "nullptr_t", nullptr_type_node);
+ /* The size and alignment of nullptr_t is the same as for a pointer to
+ character type. */
+ SET_TYPE_ALIGN (nullptr_type_node, GET_MODE_ALIGNMENT (ptr_mode));
+
input_location = save_loc;
make_fname_decl = c_make_fname_decl;
@@ -119,6 +119,8 @@ c_parse_init (void)
mask |= D_CXXONLY;
if (!flag_isoc99)
mask |= D_C99;
+ if (!flag_isoc2x)
+ mask |= D_C2X;
if (flag_no_asm)
{
mask |= D_ASM | D_EXT;
@@ -10243,6 +10245,14 @@ c_parser_postfix_expression (c_parser *parser)
"%<depend%> clause");
expr.set_error ();
break;
+ /* C23 'nullptr' literal. */
+ case RID_NULLPTR:
+ c_parser_consume_token (parser);
+ expr.value = nullptr_node;
+ set_c_expr_source_range (&expr, tok_range);
+ pedwarn_c11 (loc, OPT_Wpedantic,
+ "ISO C does not support %qs before C2X", "nullptr");
+ break;
default:
c_parser_error (parser, "expected expression");
expr.set_error ();
@@ -133,6 +133,13 @@ null_pointer_constant_p (const_tree expr)
/* This should really operate on c_expr structures, but they aren't
yet available everywhere required. */
tree type = TREE_TYPE (expr);
+
+ /* An integer constant expression with the value 0, such an expression
+ cast to type void*, or the predefined constant nullptr, are a null
+ pointer constant. */
+ if (expr == nullptr_node)
+ return true;
+
return (TREE_CODE (expr) == INTEGER_CST
&& !TREE_OVERFLOW (expr)
&& integer_zerop (expr)
@@ -4575,7 +4582,7 @@ build_unary_op (location_t location, enum tree_code code, tree xarg,
case TRUTH_NOT_EXPR:
if (typecode != INTEGER_TYPE && typecode != FIXED_POINT_TYPE
&& typecode != REAL_TYPE && typecode != POINTER_TYPE
- && typecode != COMPLEX_TYPE)
+ && typecode != COMPLEX_TYPE && typecode != NULLPTR_TYPE)
{
error_at (location,
"wrong type argument to unary exclamation mark");
@@ -5515,6 +5522,13 @@ build_conditional_expr (location_t colon_loc, tree ifexp, bool ifexp_bcp,
}
result_type = type2;
}
+ /* 6.5.15: "if one is a null pointer constant (other than a pointer) or has
+ type nullptr_t and the other is a pointer, the result type is the pointer
+ type." */
+ else if (code1 == NULLPTR_TYPE && code2 == POINTER_TYPE)
+ result_type = type2;
+ else if (code1 == POINTER_TYPE && code2 == NULLPTR_TYPE)
+ result_type = type1;
if (!result_type)
{
@@ -7613,12 +7627,13 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
error_at (location, msg);
return error_mark_node;
}
- else if (codel == POINTER_TYPE && coder == INTEGER_TYPE)
+ else if (codel == POINTER_TYPE
+ && (coder == INTEGER_TYPE || coder == NULLPTR_TYPE))
{
- /* An explicit constant 0 can convert to a pointer,
- or one that results from arithmetic, even including
- a cast to integer type. */
- if (!null_pointer_constant)
+ /* An explicit constant 0 or type nullptr_t can convert to a pointer,
+ or one that results from arithmetic, even including a cast to
+ integer type. */
+ if (!null_pointer_constant && coder != NULLPTR_TYPE)
switch (errtype)
{
case ic_argpass:
@@ -7691,7 +7706,10 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
return convert (type, rhs);
}
- else if (codel == BOOLEAN_TYPE && coder == POINTER_TYPE)
+ else if (codel == BOOLEAN_TYPE
+ /* The type nullptr_t may be converted to bool. The
+ result is false. */
+ && (coder == POINTER_TYPE || coder == NULLPTR_TYPE))
{
tree ret;
bool save = in_late_binary_op;
@@ -12107,10 +12125,10 @@ build_binary_op (location_t location, enum tree_code code,
case TRUTH_XOR_EXPR:
if ((code0 == INTEGER_TYPE || code0 == POINTER_TYPE
|| code0 == REAL_TYPE || code0 == COMPLEX_TYPE
- || code0 == FIXED_POINT_TYPE)
+ || code0 == FIXED_POINT_TYPE || code0 == NULLPTR_TYPE)
&& (code1 == INTEGER_TYPE || code1 == POINTER_TYPE
|| code1 == REAL_TYPE || code1 == COMPLEX_TYPE
- || code1 == FIXED_POINT_TYPE))
+ || code1 == FIXED_POINT_TYPE || code1 == NULLPTR_TYPE))
{
/* Result of these operations is always an int,
but that does not mean the operands should be
@@ -12418,6 +12436,27 @@ build_binary_op (location_t location, enum tree_code code,
result_type = type1;
pedwarn (location, 0, "comparison between pointer and integer");
}
+ /* 6.5.9: One of the following shall hold:
+ -- both operands have type nullptr_t; */
+ else if (code0 == NULLPTR_TYPE && code1 == NULLPTR_TYPE)
+ {
+ result_type = nullptr_type_node;
+ /* No need to convert the operands to result_type later. */
+ converted = 1;
+ }
+ /* -- one operand has type nullptr_t and the other is a null pointer
+ constant. We will have to convert the former to the type of the
+ latter, because during gimplification we can't have mismatching
+ comparison operand type. We convert from nullptr_t to the other
+ type, since only nullptr_t can be converted to nullptr_t. Also,
+ even a constant 0 is a null pointer constant, so we may have to
+ create a pointer type from its type. */
+ else if (code0 == NULLPTR_TYPE && null_pointer_constant_p (orig_op1))
+ result_type = (INTEGRAL_TYPE_P (type1)
+ ? build_pointer_type (type1) : type1);
+ else if (code1 == NULLPTR_TYPE && null_pointer_constant_p (orig_op0))
+ result_type = (INTEGRAL_TYPE_P (type0)
+ ? build_pointer_type (type0) : type0);
if ((TREE_CODE (TREE_TYPE (orig_op0)) == BOOLEAN_TYPE
|| truth_value_p (TREE_CODE (orig_op0)))
^ (TREE_CODE (TREE_TYPE (orig_op1)) == BOOLEAN_TYPE
@@ -187,9 +187,6 @@ enum cp_tree_index
CPTI_NOEXCEPT_FALSE_SPEC,
CPTI_NOEXCEPT_DEFERRED_SPEC,
- CPTI_NULLPTR,
- CPTI_NULLPTR_TYPE,
-
CPTI_ANY_TARG,
CPTI_MODULE_HWM,
@@ -254,8 +251,6 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
#define conv_op_marker cp_global_trees[CPTI_CONV_OP_MARKER]
#define abort_fndecl cp_global_trees[CPTI_ABORT_FNDECL]
#define current_aggr cp_global_trees[CPTI_AGGR_TAG]
-#define nullptr_node cp_global_trees[CPTI_NULLPTR]
-#define nullptr_type_node cp_global_trees[CPTI_NULLPTR_TYPE]
/* std::align_val_t */
#define align_type_node cp_global_trees[CPTI_ALIGN_TYPE]
@@ -4405,9 +4400,6 @@ get_vec_init_expr (tree t)
|| TREE_CODE (TYPE) == REAL_TYPE \
|| TREE_CODE (TYPE) == COMPLEX_TYPE)
-/* True iff TYPE is cv decltype(nullptr). */
-#define NULLPTR_TYPE_P(TYPE) (TREE_CODE (TYPE) == NULLPTR_TYPE)
-
/* [basic.types]
Arithmetic types, enumeration types, pointer types,
@@ -4793,16 +4793,10 @@ cxx_init_decl_processing (void)
}
}
- nullptr_type_node = make_node (NULLPTR_TYPE);
- TYPE_SIZE (nullptr_type_node) = bitsize_int (GET_MODE_BITSIZE (ptr_mode));
- TYPE_SIZE_UNIT (nullptr_type_node) = size_int (GET_MODE_SIZE (ptr_mode));
- TYPE_UNSIGNED (nullptr_type_node) = 1;
- TYPE_PRECISION (nullptr_type_node) = GET_MODE_BITSIZE (ptr_mode);
+ /* C++-specific nullptr initialization. */
if (abi_version_at_least (9))
SET_TYPE_ALIGN (nullptr_type_node, GET_MODE_ALIGNMENT (ptr_mode));
- SET_TYPE_MODE (nullptr_type_node, ptr_mode);
record_builtin_type (RID_MAX, "decltype(nullptr)", nullptr_type_node);
- nullptr_node = build_int_cst (nullptr_type_node, 0);
}
if (! supports_one_only ())
@@ -443,6 +443,14 @@ typedef struct {
#endif
#endif /* C++11. */
+#if (defined (__STDC_VERSION__) && __STDC_VERSION__ > 201710L)
+#ifndef _GCC_NULLPTR_T
+#define _GCC_NULLPTR_T
+ typedef __typeof__(nullptr) nullptr_t;
+/* ??? This doesn't define __STDC_VERSION_STDDEF_H__ yet. */
+#endif
+#endif /* C23. */
+
#endif /* _STDDEF_H was defined this time */
#endif /* !_STDDEF_H && !_STDDEF_H_ && !_ANSI_STDDEF_H && !__STDDEF_H__
new file mode 100644
@@ -0,0 +1,10 @@
+/* Test that in pre-C23 modes, nullptr is a normal identifier,
+ not a keyword. */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+int nullptr;
+
+void
+f (int nullptr)
+{
+}
new file mode 100644
@@ -0,0 +1,10 @@
+/* Test that in pre-C23 modes, nullptr is a normal identifier,
+ not a keyword. */
+/* { dg-options "-std=c17 -pedantic-errors" } */
+
+int nullptr;
+
+void
+f (int nullptr)
+{
+}
new file mode 100644
@@ -0,0 +1,10 @@
+/* Test that we don't predefine `nullptr' pre-C2X. */
+/* { dg-do compile } */
+/* { dg-options "-std=c17 -pedantic-errors" } */
+
+int *
+fn (int *p)
+{
+ p = nullptr; /* { dg-error "'nullptr' undeclared" } */
+ return p;
+}
new file mode 100644
@@ -0,0 +1,259 @@
+/* Test valid usage of C23 nullptr. */
+/* { dg-do run } */
+/* { dg-options "-std=c2x -pedantic-errors -Wall -Wextra -Wno-unused-variable" } */
+
+#include <stdarg.h>
+
+typedef __typeof__(nullptr) nullptr_t;
+
+void f1 (nullptr_t) { }
+void f2 (int *) { }
+void f3 (_Bool) { }
+nullptr_t cmp (void) { return nullptr; }
+
+/* The type nullptr_t shall not be converted to any type other than void, bool or
+ a pointer type. No type other than nullptr_t shall be converted to nullptr_t. */
+void
+test1 (void)
+{
+ const nullptr_t nptr = nullptr;
+ static nullptr_t static_nptr;
+ int *p1 = nullptr;
+ void *p2 = nullptr;
+ float *p3 = nullptr;
+ void (*p4)(int) = nullptr;
+ int (*p5)[10] = nullptr;
+ int *p6 = nptr;
+ void *p7 = nptr;
+ float *p8 = nptr;
+ void (*p9)(int) = nptr;
+ int (*p10)[10] = nptr;
+ int *p11 = (int *) nullptr;
+ int *p12 = (int *) nptr;
+ if (nullptr || p1 || p2 || p3 || p4 || p5 || p6 || p7 || p8 || p9 || p10
+ || p11 || p12)
+ __builtin_abort ();
+
+ _Bool b1 = nullptr;
+ _Bool b2 = (_Bool) nullptr;
+ _Bool b3 = nptr;
+ _Bool b4 = (_Bool) nptr;
+ if (b1 || b2 || b3 || b4 || (_Bool) nullptr || (_Bool) nptr)
+ __builtin_abort ();
+
+ __auto_type a1 = nullptr;
+ __auto_type a2 = nptr;
+
+ /* We can convert nullptr_t to nullptr_t. */
+ __typeof__(nullptr) x = nullptr;
+ f1 (x);
+ f1 (nullptr);
+ f2 (x);
+ f2 (nullptr);
+ f3 (nullptr);
+
+ const nullptr_t np1 = nullptr;
+ const nullptr_t np2 = np1;
+ (void) nullptr;
+ (void) np1;
+ (void) np2;
+ (void) cmp ();
+ (void)(nullptr_t) nullptr;
+}
+
+/* Test valid comparison. */
+void
+test2 (int *p)
+{
+ /* If both operands have type nullptr_t or one operand has type nullptr_t
+ and the other is a null pointer constant, they compare equal. */
+ const nullptr_t nptr = nullptr;
+ int r = 0;
+
+ /* Both operands have type nullptr_t. */
+ r |= nullptr != nullptr;
+ r |= cmp () != nullptr;
+ r |= nullptr != cmp ();
+ r |= !(nullptr == nullptr);
+ r |= !(cmp () == nullptr);
+ r |= !(nullptr == cmp ());
+ r |= nptr != nptr;
+ r |= cmp () != nptr;
+ r |= nptr != cmp ();
+ r |= !(nptr == nptr);
+ r |= !(cmp () == nptr);
+ r |= !(nptr == cmp ());
+
+ /* One operand has type nullptr_t and the other is a null pointer constant. */
+ r |= nullptr != (void *) 0;
+ r |= (nullptr) != (void *) 0;
+ r |= !(nullptr == (void *) 0);
+ r |= (void *) 0 != nullptr;
+ r |= (void *) 0 != (nullptr);
+ r |= !((void *) 0 == nullptr);
+ r |= nullptr != 0;
+ r |= (nullptr) != 0;
+ r |= 0 != nullptr;
+ r |= 0 != (nullptr);
+ r |= !(nullptr == 0);
+ r |= !(0 == nullptr);
+ r |= nullptr != 0u;
+ r |= 0u != nullptr;
+ r |= !(nullptr == 0u);
+ r |= !(0u == nullptr);
+ r |= nptr != (void *) 0;
+ r |= !(nptr == (void *) 0);
+ r |= (void *) 0 != nptr;
+ r |= !((void *) 0 == nptr);
+ r |= nptr != 0;
+ r |= 0 != nptr;
+ r |= !(nptr == 0);
+ r |= !(0 == nptr);
+ r |= nptr != 0u;
+ r |= 0u != nptr;
+ r |= !(nptr == 0u);
+ r |= !(0u == nptr);
+ if (r)
+ __builtin_abort ();
+
+ /* One operand is a pointer and the other is a null pointer constant. */
+ (void) (p == nullptr);
+ (void) (p != nullptr);
+ (void) (nullptr == p);
+ (void) (nullptr != p);
+ (void) (p == (nullptr));
+ (void) (p != (nullptr));
+ (void) ((nullptr) == p);
+ (void) ((nullptr) != p);
+ (void) ((void *)nullptr == nullptr);
+ (void) ((void *)nullptr != nullptr);
+ (void) (nullptr == (void *)nullptr);
+ (void) (nullptr != (void *)nullptr);
+}
+
+/* Test ?:. */
+void
+test3 (int *p, _Bool b)
+{
+ int x = nullptr ? 1 : 2;
+ (void) x;
+ const nullptr_t nptr = nullptr;
+ /* One of the following shall hold for the second and third operands:
+ -- both operands have nullptr_t type. */
+ __auto_type r1 = b ? nullptr : nullptr;
+ __auto_type r2 = b ? nptr : nptr;
+ /* -- one operand is a pointer and the other is a null pointer constant
+ or has type nullptr_t; */
+ __auto_type r3 = b ? p : nullptr;
+ __auto_type r4 = b ? nullptr : p;
+ __auto_type r5 = b ? nptr : p;
+ __auto_type r6 = b ? p : nptr;
+ __auto_type r7 = b ? 0 : p;
+ __auto_type r8 = b ? p : 0;
+ __auto_type r9 = b ? p : cmp ();
+ __auto_type r10 = b ? cmp () : p;
+}
+
+/* Simple assignment. */
+void
+test4 (void)
+{
+ /* -- the left operand has an atomic, qualified, or unqualified version of
+ the nullptr_t type and the type of the right is nullptr_t; */
+ nullptr_t n1;
+ n1 = nullptr;
+ const nullptr_t n2 = nullptr;
+ _Atomic nullptr_t n3 = nullptr;
+ volatile nullptr_t n4 = nullptr;
+ /* -- the left operand is an atomic, qualified, or unqualified pointer,
+ and the type of the right is nullptr_t; */
+ int *p1 = cmp ();
+ _Atomic int *p2 = cmp ();
+ const int *volatile p3 = cmp ();
+ const int *const *const p4 = cmp ();
+ double (*const p5)(void) = n1;
+ /* -- the left operand is an atomic, qualified, or unqualified bool, and
+ the type of the right is nullptr_t; */
+ _Bool b1;
+ b1 = cmp ();
+ const _Bool b2 = nullptr;
+ _Atomic _Bool b3;
+ b3 = n1;
+ (void) b1;
+ (void) b3;
+}
+
+/* var_arg etc. */
+static void
+test5 (int i, ...)
+{
+ va_list ap;
+ va_start (ap, i);
+ if (va_arg (ap, void *))
+ __builtin_abort ();
+}
+
+/* Operand of alignas, sizeof or typeof operators. */
+void
+test6 (void)
+{
+ _Static_assert (sizeof (nullptr) == sizeof (void *), "sizeof (nullptr)");
+ _Static_assert (sizeof (nullptr_t) == sizeof (void *), "sizeof (nullptr_t)");
+ _Static_assert (sizeof (nullptr) == sizeof (char *), "sizeof (nullptr)");
+ _Static_assert (sizeof (nullptr_t) == sizeof (char *), "sizeof (nullptr_t)");
+ _Static_assert (_Alignof (nullptr_t) == _Alignof (char *), "_Alignof (nullptr_t)");
+ __typeof__(nullptr) t = nullptr;
+ f1 (t);
+ _Alignas (nullptr_t) char i1 = 'q';
+
+ _Static_assert (_Generic (nullptr, nullptr_t: 1, default: 0) == 1, "_Generic");
+ _Static_assert (_Generic (t, nullptr_t: 1, default: 0) == 1, "_Generic");
+ _Static_assert (_Generic (cmp (), nullptr_t: 1, default: 0) == 1, "_Generic");
+ _Static_assert (_Generic (0, nullptr_t: 1, int: 2, default: 0) == 2, "_Generic");
+ _Static_assert (_Generic ((void *)0, nullptr_t: 1, void *: 2, default: 0) == 2, "_Generic");
+ _Static_assert (_Generic (nullptr, nullptr_t: 1, void *: 2, default: 0) == 1, "_Generic");
+}
+
+/* Play with !, ||, &&. */
+void
+test7 (void)
+{
+ if (nullptr)
+ __builtin_abort ();
+ if (1 && nullptr)
+ __builtin_abort ();
+ if (0 || nullptr)
+ __builtin_abort ();
+ if (nullptr && 1)
+ __builtin_abort ();
+ if (nullptr || 0)
+ __builtin_abort ();
+ if (!nullptr)
+ {
+ }
+ else
+ __builtin_abort ();
+ while (nullptr)
+ __builtin_abort ();
+ int i = 0;
+ do
+ ++i;
+ while (nullptr);
+ if (i != 1)
+ __builtin_abort ();
+ for (;nullptr;)
+ __builtin_abort ();
+}
+
+int
+main (void)
+{
+ int i = 42;
+ test1 ();
+ test2 (&i);
+ test3 (&i, 0);
+ test4 ();
+ test5 (42, nullptr);
+ test6 ();
+ test7 ();
+}
new file mode 100644
@@ -0,0 +1,9 @@
+/* Test nullptr_t from <stddef.h.. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#include <stddef.h>
+
+void f(nullptr_t);
+_Static_assert (sizeof (nullptr_t) == sizeof (char *), "sizeof (nullptr_t)");
+_Static_assert (_Alignof (nullptr_t) == _Alignof (char *), "_Alignof (nullptr_t)");
new file mode 100644
@@ -0,0 +1,78 @@
+/* Test wrong usage of C23 nullptr. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wall -Wextra -Wno-unused-variable" } */
+
+typedef __typeof__(nullptr) nullptr_t;
+
+void g (nullptr_t); /* { dg-message "expected .nullptr_t. but argument is of type .int." } */
+nullptr_t cmp (void);
+
+void
+test1 (int *p)
+{
+ (void) (p > nullptr); /* { dg-error "ordered comparison" } */
+ (void) (p >= nullptr); /* { dg-error "ordered comparison" } */
+ (void) (p < nullptr); /* { dg-error "ordered comparison" } */
+ (void) (p <= nullptr); /* { dg-error "ordered comparison" } */
+ (void) (nullptr == 1); /* { dg-error "invalid operands" } */
+ (void) (1 == nullptr); /* { dg-error "invalid operands" } */
+ (void) (nullptr != 1); /* { dg-error "invalid operands" } */
+ (void) (1 != nullptr); /* { dg-error "invalid operands" } */
+ (void) (1 > nullptr); /* { dg-error "invalid operands" } */
+
+ /* "(nullptr_t)nullptr" has type nullptr_t but isn't an NPC. */
+ (void) ((nullptr_t)nullptr == p); /* { dg-error "invalid operands" } */
+ (void) ((nullptr_t)nullptr != p); /* { dg-error "invalid operands" } */
+ (void) (p == (nullptr_t)nullptr); /* { dg-error "invalid operands" } */
+ (void) (p != (nullptr_t)nullptr); /* { dg-error "invalid operands" } */
+ (void) (cmp () == p); /* { dg-error "invalid operands" } */
+ (void) (cmp () != p); /* { dg-error "invalid operands" } */
+ (void) (p == cmp ()); /* { dg-error "invalid operands" } */
+ (void) (p != cmp ()); /* { dg-error "invalid operands" } */
+ /* "(void *)nullptr" is not an NPC, either. */
+ (void) ((void *)nullptr == cmp ()); /* { dg-error "invalid operands" } */
+ (void) ((void *)nullptr != cmp ()); /* { dg-error "invalid operands" } */
+ (void) (cmp () == (void *)nullptr); /* { dg-error "invalid operands" } */
+ (void) (cmp () != (void *)nullptr); /* { dg-error "invalid operands" } */
+}
+
+void
+test2 (void)
+{
+ const nullptr_t nptr = nullptr;
+ int p = nullptr; /* { dg-error "incompatible types" } */
+ float d = nullptr; /* { dg-error "incompatible types" } */
+ char arr[10] = { nullptr }; /* { dg-error "incompatible types" } */
+
+ /* No type other than nullptr_t shall be converted to nullptr_t. */
+ const nullptr_t n = 0; /* { dg-error "invalid initializer" } */
+ +(nullptr_t) 0; /* { dg-error "conversion from .int. to .nullptr_t." } */
+
+ g (0); /* { dg-error "incompatible type" } */
+
+ int i = 42 + nullptr; /* { dg-error "invalid operands" } */
+
+ /* The assignment of an object of type nullptr_t with a value of another
+ type, even if the value is a null pointer constant, is a constraint
+ violation. */
+ nullptr_t m;
+ m = 0; /* { dg-error "incompatible types" } */
+ (void) m;
+ nullptr_t o = 0; /* { dg-error "invalid initializer" } */
+
+ switch (nullptr); /* { dg-error "switch quantity not an integer" } */
+}
+
+/* If a second or third operand of type nullptr_t is used that is not a null
+ pointer constant and the other operand is not a pointer or does not have
+ itself nullptr_t, a constraint is violated even if that other operand is
+ a null pointer constant such as 0. */
+void
+test3 (_Bool b, int i)
+{
+ const nullptr_t nptr = nullptr;
+ __auto_type a1 = b ? nptr : i; /* { dg-error "type mismatch" } */
+ __auto_type a2 = b ? i : nptr; /* { dg-error "type mismatch" } */
+ __auto_type a3 = b ? nptr : 0; /* { dg-error "type mismatch" } */
+ __auto_type a4 = b ? 0 : nptr; /* { dg-error "type mismatch" } */
+}
new file mode 100644
@@ -0,0 +1,11 @@
+/* Test that -Wc11-c2x-compat issues a warning (not a pedwarn) about
+ `nullptr' in C2X. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wc11-c2x-compat" } */
+
+int *
+fn (int *p)
+{
+ p = nullptr; /* { dg-warning "ISO C does not support .nullptr. before C2X" } */
+ return p;
+}
new file mode 100644
@@ -0,0 +1,14 @@
+/* Test that we don't lose side-effects when converting from nullptr_t. */
+/* { dg-do run } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+int i;
+nullptr_t fn () { ++i; return nullptr; }
+
+int
+main ()
+{
+ int *p = fn ();
+ if (i != 1)
+ __builtin_abort ();
+}