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c++: Fix NaN as C++20 template argument

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C++20 allows floating-point types for non-type template parameters;
floating-point values are considered to be equivalent template arguments if
they are "identical", which conveniently seems to map onto an existing GCC
predicate.

gcc/cp/ChangeLog:

	* tree.c (cp_tree_equal): Use real_identical.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/nontype-float1.C: New test.
This commit is contained in:
Jason Merrill 2021-03-16 16:06:27 -04:00
parent 0251051db6
commit a4101e5aaf
2 changed files with 13 additions and 1 deletions
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2
gcc/cp/tree.c
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@ -3740,7 +3740,7 @@ cp_tree_equal (tree t1, tree t2)
return tree_int_cst_equal (t1, t2);
case REAL_CST:
return real_equal (&TREE_REAL_CST (t1), &TREE_REAL_CST (t2));
return real_identical (&TREE_REAL_CST (t1), &TREE_REAL_CST (t2));
case STRING_CST:
return TREE_STRING_LENGTH (t1) == TREE_STRING_LENGTH (t2)

12
gcc/testsuite/g++.dg/cpp2a/nontype-float1.C Normal file
View file

@ -0,0 +1,12 @@
// { dg-do compile { target c++20 } }
#include <cmath>
template<auto> class MyClass { };
static_assert(__is_same(MyClass<NAN>, MyClass<NAN>));
constexpr auto mynan = NAN;
static_assert(__is_same(MyClass<mynan>, MyClass<mynan>));
static_assert(__is_same(MyClass<NAN>, MyClass<mynan>));