| Message ID | 20240401175034.44681-1-polacek@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: make __is_array return false for T[0] [PR114479] | expand |
On 4/1/24 13:50, Marek Polacek wrote: > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > -- >8 -- > When we switched to using the __is_array built-in trait to implement > std::is_array in r14-6623-g7fd9c349e45534, we started saying that > T[0] is an array. There are various opinions as to whether that is > the best answer, but it seems prudent to keep the GCC 13 result. > > PR c++/114479 > > gcc/cp/ChangeLog: > > * semantics.cc (trait_expr_value) <case CPTK_IS_ARRAY>: Return false > for zero-sized arrays. > > gcc/testsuite/ChangeLog: > > * g++.dg/ext/is_array.C: Extend. > --- > gcc/cp/semantics.cc | 4 +++- > gcc/testsuite/g++.dg/ext/is_array.C | 12 ++++++++++++ > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc > index 9838331d2a9..f561c119dfd 100644 > --- a/gcc/cp/semantics.cc > +++ b/gcc/cp/semantics.cc > @@ -12439,7 +12439,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2) > return CP_AGGREGATE_TYPE_P (type1); > > case CPTK_IS_ARRAY: > - return type_code1 == ARRAY_TYPE; > + return (type_code1 == ARRAY_TYPE > + /* We don't want to report T[0] as being an array type. */ Please elaborate that this is for compatibility with an implementation of is_array by template argument deduction, because compute_array_index_type_loc rejects a zero-size array in SFINAE context. OK with that adjustment. > + && !(TYPE_SIZE (type1) && integer_zerop (TYPE_SIZE (type1)))); > > case CPTK_IS_ASSIGNABLE: > return is_xible (MODIFY_EXPR, type1, type2); > diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C > index f1a6e08b87a..84993266629 100644 > --- a/gcc/testsuite/g++.dg/ext/is_array.C > +++ b/gcc/testsuite/g++.dg/ext/is_array.C > @@ -1,4 +1,5 @@ > // { dg-do compile { target c++11 } } > +// { dg-options "" } > > #define SA(X) static_assert((X),#X) > > @@ -10,18 +11,29 @@ > > class ClassType { }; > > +constexpr int sz0 = 0; > +constexpr int sz2 = 2; > + > SA_TEST_CATEGORY(__is_array, int[2], true); > SA_TEST_CATEGORY(__is_array, int[], true); > +SA_TEST_CATEGORY(__is_array, int[0], false); > SA_TEST_CATEGORY(__is_array, int[2][3], true); > SA_TEST_CATEGORY(__is_array, int[][3], true); > +SA_TEST_CATEGORY(__is_array, int[0][3], false); > +SA_TEST_CATEGORY(__is_array, int[3][0], false); > SA_TEST_CATEGORY(__is_array, float*[2], true); > SA_TEST_CATEGORY(__is_array, float*[], true); > SA_TEST_CATEGORY(__is_array, float*[2][3], true); > SA_TEST_CATEGORY(__is_array, float*[][3], true); > SA_TEST_CATEGORY(__is_array, ClassType[2], true); > SA_TEST_CATEGORY(__is_array, ClassType[], true); > +SA_TEST_CATEGORY(__is_array, ClassType[0], false); > SA_TEST_CATEGORY(__is_array, ClassType[2][3], true); > SA_TEST_CATEGORY(__is_array, ClassType[][3], true); > +SA_TEST_CATEGORY(__is_array, ClassType[0][3], false); > +SA_TEST_CATEGORY(__is_array, ClassType[2][0], false); > +SA_TEST_CATEGORY(__is_array, int[sz2], true); > +SA_TEST_CATEGORY(__is_array, int[sz0], false); > > // Sanity check. > SA_TEST_CATEGORY(__is_array, ClassType, false); > > base-commit: bba118db3f63cb1e3953a014aa3ac2ad89908950
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc index 9838331d2a9..f561c119dfd 100644 --- a/gcc/cp/semantics.cc +++ b/gcc/cp/semantics.cc @@ -12439,7 +12439,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2) return CP_AGGREGATE_TYPE_P (type1); case CPTK_IS_ARRAY: - return type_code1 == ARRAY_TYPE; + return (type_code1 == ARRAY_TYPE + /* We don't want to report T[0] as being an array type. */ + && !(TYPE_SIZE (type1) && integer_zerop (TYPE_SIZE (type1)))); case CPTK_IS_ASSIGNABLE: return is_xible (MODIFY_EXPR, type1, type2); diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C index f1a6e08b87a..84993266629 100644 --- a/gcc/testsuite/g++.dg/ext/is_array.C +++ b/gcc/testsuite/g++.dg/ext/is_array.C @@ -1,4 +1,5 @@ // { dg-do compile { target c++11 } } +// { dg-options "" } #define SA(X) static_assert((X),#X) @@ -10,18 +11,29 @@ class ClassType { }; +constexpr int sz0 = 0; +constexpr int sz2 = 2; + SA_TEST_CATEGORY(__is_array, int[2], true); SA_TEST_CATEGORY(__is_array, int[], true); +SA_TEST_CATEGORY(__is_array, int[0], false); SA_TEST_CATEGORY(__is_array, int[2][3], true); SA_TEST_CATEGORY(__is_array, int[][3], true); +SA_TEST_CATEGORY(__is_array, int[0][3], false); +SA_TEST_CATEGORY(__is_array, int[3][0], false); SA_TEST_CATEGORY(__is_array, float*[2], true); SA_TEST_CATEGORY(__is_array, float*[], true); SA_TEST_CATEGORY(__is_array, float*[2][3], true); SA_TEST_CATEGORY(__is_array, float*[][3], true); SA_TEST_CATEGORY(__is_array, ClassType[2], true); SA_TEST_CATEGORY(__is_array, ClassType[], true); +SA_TEST_CATEGORY(__is_array, ClassType[0], false); SA_TEST_CATEGORY(__is_array, ClassType[2][3], true); SA_TEST_CATEGORY(__is_array, ClassType[][3], true); +SA_TEST_CATEGORY(__is_array, ClassType[0][3], false); +SA_TEST_CATEGORY(__is_array, ClassType[2][0], false); +SA_TEST_CATEGORY(__is_array, int[sz2], true); +SA_TEST_CATEGORY(__is_array, int[sz0], false); // Sanity check. SA_TEST_CATEGORY(__is_array, ClassType, false);