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From: Joseph Myers <jsm28@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-5767] c: Allow conversions of null pointer constants to nullptr_t Date: Fri, 10 Feb 2023 00:43:24 +0000 (GMT) [thread overview] Message-ID: <20230210004324.54C1C3858C60@sourceware.org> (raw) https://gcc.gnu.org/g:b9f8935e110c392c21460db838b4209c32f070c2 commit r13-5767-gb9f8935e110c392c21460db838b4209c32f070c2 Author: Joseph Myers <joseph@codesourcery.com> Date: Fri Feb 10 00:42:47 2023 +0000 c: Allow conversions of null pointer constants to nullptr_t WG14 has agreed to allow conversions (explicit and implicit) from null pointer constants to nullptr_t; update GCC's nullptr_t implementation to match. Bootstrapped with no regressions for x86_64-pc-linux-gnu. gcc/c/ * c-convert.cc (c_convert): Allow conversion of a null pointer constant to nullptr_t. * c-typeck.cc (null_pointer_constant_p): Remove static. (convert_for_assignment): Allow conversion of a null pointer constant to nullptr_t. (digest_init): Handle NULLPTR_TYPE among scalar conversions. * c-tree.h (null_pointer_constant_p): Declare. gcc/testsuite/ * gcc.dg/c2x-nullptr-1.c: Test conversion of null pointer constants to nullptr_t. * gcc.dg/c2x-nullptr-3.c: Do not expect errors for conversion of null pointer constants to nullptr_t. Do test errors for conversion of other values to nullptr_t and for unary '+' on nullptr_t. Diff: --- gcc/c/c-convert.cc | 21 ++++++++++++++++++--- gcc/c/c-tree.h | 1 + gcc/c/c-typeck.cc | 7 ++++--- gcc/testsuite/gcc.dg/c2x-nullptr-1.c | 16 ++++++++++++++-- gcc/testsuite/gcc.dg/c2x-nullptr-3.c | 19 +++++++++++-------- 5 files changed, 48 insertions(+), 16 deletions(-) diff --git a/gcc/c/c-convert.cc b/gcc/c/c-convert.cc index dccd245dfc3..0f35dc4fe9a 100644 --- a/gcc/c/c-convert.cc +++ b/gcc/c/c-convert.cc @@ -157,6 +157,19 @@ c_convert (tree type, tree expr, bool init_const) ret = convert_to_pointer (type, e); goto maybe_fold; + case NULLPTR_TYPE: + /* A null pointer constant or value of type nullptr_t may be + converted to nullptr_t. The latter case has already been + handled. build_c_cast will create an additional NOP_EXPR to + ensure the result of the conversion is not itself a null + pointer constant. */ + if (null_pointer_constant_p (expr)) + { + ret = build_int_cst (type, 0); + goto maybe_fold; + } + break; + case REAL_TYPE: ret = convert_to_real (type, e); goto maybe_fold; @@ -201,12 +214,14 @@ c_convert (tree type, tree expr, bool init_const) } /* 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. */ + the nullptr_t type is a scalar type. Only nullptr_t or a null pointer + constant 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); + inform (input_location, + "only %qT or a null pointer constant can be converted to %qT", + type, type); } else error ("conversion to non-scalar type requested"); diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h index 00ccf87e6e6..e5eefe6bbba 100644 --- a/gcc/c/c-tree.h +++ b/gcc/c/c-tree.h @@ -728,6 +728,7 @@ extern location_t c_last_sizeof_loc; extern struct c_switch *c_switch_stack; +extern bool null_pointer_constant_p (const_tree); extern bool char_type_p (tree); extern tree c_objc_common_truthvalue_conversion (location_t, tree); extern tree require_complete_type (location_t, tree); diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc index 157b77eda95..e37b0973cd6 100644 --- a/gcc/c/c-typeck.cc +++ b/gcc/c/c-typeck.cc @@ -89,7 +89,6 @@ static bool require_constant_value; static bool require_constant_elements; static bool require_constexpr_value; -static bool null_pointer_constant_p (const_tree); static tree qualify_type (tree, tree); static int tagged_types_tu_compatible_p (const_tree, const_tree, bool *, bool *); @@ -130,7 +129,7 @@ static int comptypes_internal (const_tree, const_tree, bool *, bool *); \f /* Return true if EXP is a null pointer constant, false otherwise. */ -static bool +bool null_pointer_constant_p (const_tree expr) { /* This should really operate on c_expr structures, but they aren't @@ -7837,6 +7836,8 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type, in_late_binary_op = save; return ret; } + else if (codel == NULLPTR_TYPE && null_pointer_constant) + return convert (type, rhs); switch (errtype) { @@ -8596,7 +8597,7 @@ digest_init (location_t init_loc, tree type, tree init, tree origtype, if (code == INTEGER_TYPE || code == REAL_TYPE || code == FIXED_POINT_TYPE || code == POINTER_TYPE || code == ENUMERAL_TYPE || code == BOOLEAN_TYPE - || code == COMPLEX_TYPE || code == VECTOR_TYPE) + || code == COMPLEX_TYPE || code == VECTOR_TYPE || code == NULLPTR_TYPE) { tree unconverted_init = inside_init; if (TREE_CODE (TREE_TYPE (init)) == ARRAY_TYPE diff --git a/gcc/testsuite/gcc.dg/c2x-nullptr-1.c b/gcc/testsuite/gcc.dg/c2x-nullptr-1.c index 04f9901bb12..4e440234d52 100644 --- a/gcc/testsuite/gcc.dg/c2x-nullptr-1.c +++ b/gcc/testsuite/gcc.dg/c2x-nullptr-1.c @@ -11,8 +11,9 @@ 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. */ +/* 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 or a null pointer constant + shall be converted to nullptr_t. */ void test1 (void) { @@ -63,6 +64,17 @@ test1 (void) (void) np2; (void) cmp (); (void)(nullptr_t) nullptr; + + const nullptr_t n = 0; + (void) (nullptr_t) 0; + + f1 (0); + f1 ((void *) 0); + f1 (0L); + nullptr_t n2; + n2 = (void *) 0; + n2 = 123 - 123; + (void) n2; } /* Test valid comparison. */ diff --git a/gcc/testsuite/gcc.dg/c2x-nullptr-3.c b/gcc/testsuite/gcc.dg/c2x-nullptr-3.c index 591ab7e6158..09d9856ef97 100644 --- a/gcc/testsuite/gcc.dg/c2x-nullptr-3.c +++ b/gcc/testsuite/gcc.dg/c2x-nullptr-3.c @@ -29,21 +29,24 @@ test2 (void) 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" } */ + /* Unary '+' is not valid for nullptr. */ + +nullptr; /* { dg-error "wrong type argument to unary plus" } */ + g (0.0); /* { dg-error "incompatible type" } */ + g (1); /* { dg-error "incompatible type" } */ + g ((int) (float) 0.0); /* { 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 + type, other than a null pointer constant, is a constraint violation. */ nullptr_t m; - m = 0; /* { dg-error "incompatible types" } */ + m = 1; /* { dg-error "incompatible types" } */ + m = 0.0; /* { dg-error "incompatible types" } */ (void) m; - nullptr_t o = 0; /* { dg-error "invalid initializer" } */ + nullptr_t o = 1; /* { dg-error "incompatible types" } */ + (nullptr_t) 0.0; /* { dg-error "conversion" } */ + (nullptr_t) (int) (float) 0.0; /* { dg-error "conversion" } */ switch (nullptr); /* { dg-error "switch quantity not an integer" } */ }
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