[gcc r16-8556] libstdc++: Remove span constructor from initializer_list.
Tomasz Kaminski
tkaminsk@gcc.gnu.org
Fri Apr 10 06:06:42 GMT 2026
https://gcc.gnu.org/g:bd29a35496cf377c98bebdc3b3a9d8bc2772009b
commit r16-8556-gbd29a35496cf377c98bebdc3b3a9d8bc2772009b
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date: Wed Apr 8 17:29:07 2026 +0200
libstdc++: Remove span constructor from initializer_list.
Following LWG4520 resolution from paper
P4144R1 Remove span’s initializer_list constructor for C++26.
libstdc++-v3/ChangeLog:
* include/bits/version.def (span_initializer_list): Remove.
* include/bits/version.h: Regenerate.
* include/std/span (span::span(initializer_list<value_type>)):
Remove.
* testsuite/23_containers/span/init_list_cons.cc: Removed.
* testsuite/23_containers/span/init_list_cons_neg.cc: Removed.
* testsuite/23_containers/inplace_vector/copy.cc: Replace span
with initializer_list in eq helper.
* testsuite/23_containers/inplace_vector/erasure.cc: Likewise.
* testsuite/23_containers/inplace_vector/move.cc: Likewise.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
Diff:
---
libstdc++-v3/include/bits/version.def | 8 ---
libstdc++-v3/include/bits/version.h | 10 ----
libstdc++-v3/include/std/span | 16 +-----
.../testsuite/23_containers/inplace_vector/copy.cc | 2 +-
.../23_containers/inplace_vector/erasure.cc | 11 +---
.../testsuite/23_containers/inplace_vector/move.cc | 2 +-
.../testsuite/23_containers/span/init_list_cons.cc | 65 ----------------------
.../23_containers/span/init_list_cons_neg.cc | 36 ------------
8 files changed, 6 insertions(+), 144 deletions(-)
diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index 9a3b3655974c..059c38c6c13d 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2171,14 +2171,6 @@ ftms = {
};
};
-ftms = {
- name = span_initializer_list;
- values = {
- v = 202311;
- cxxmin = 26;
- };
-};
-
ftms = {
name = text_encoding;
values = {
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index 8f541fc389ec..f806e8f3f9c0 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2426,16 +2426,6 @@
#endif /* !defined(__cpp_lib_saturation_arithmetic) */
#undef __glibcxx_want_saturation_arithmetic
-#if !defined(__cpp_lib_span_initializer_list)
-# if (__cplusplus > 202302L)
-# define __glibcxx_span_initializer_list 202311L
-# if defined(__glibcxx_want_all) || defined(__glibcxx_want_span_initializer_list)
-# define __cpp_lib_span_initializer_list 202311L
-# endif
-# endif
-#endif /* !defined(__cpp_lib_span_initializer_list) */
-#undef __glibcxx_want_span_initializer_list
-
#if !defined(__cpp_lib_text_encoding)
# if (__cplusplus > 202302L) && _GLIBCXX_HOSTED && (_GLIBCXX_USE_NL_LANGINFO_L)
# define __glibcxx_text_encoding 202306L
diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span
index a2f338449c8a..a5f5bf48f90e 100644
--- a/libstdc++-v3/include/std/span
+++ b/libstdc++-v3/include/std/span
@@ -47,9 +47,7 @@
#include <cstddef>
#include <bits/stl_iterator.h>
#include <bits/ranges_base.h>
-#ifdef __cpp_lib_span_initializer_list
-# include <initializer_list>
-#endif
+
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -232,18 +230,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _M_ptr(ranges::data(__range)), _M_extent(ranges::size(__range))
{ }
-#if __cpp_lib_span_initializer_list >= 202311L // >= C++26
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Winit-list-lifetime"
- constexpr
- explicit(extent != dynamic_extent)
- span(initializer_list<value_type> __il)
- requires (is_const_v<_Type>)
- : _M_ptr(__il.begin()), _M_extent(__il.size())
- { }
-#pragma GCC diagnostic pop
-#endif
-
constexpr
span(const span&) noexcept = default;
diff --git a/libstdc++-v3/testsuite/23_containers/inplace_vector/copy.cc b/libstdc++-v3/testsuite/23_containers/inplace_vector/copy.cc
index 917eebd80f7c..11260c63313c 100644
--- a/libstdc++-v3/testsuite/23_containers/inplace_vector/copy.cc
+++ b/libstdc++-v3/testsuite/23_containers/inplace_vector/copy.cc
@@ -138,7 +138,7 @@ static_assert(std::is_trivially_copy_assignable_v<std::inplace_vector<Z, 0>>);
template<typename T, size_t N>
constexpr bool
-eq(const std::inplace_vector<T, N>& s, std::span<const T> o)
+eq(const std::inplace_vector<T, N>& s, std::initializer_list<std::type_identity_t<T>> o)
{ return std::ranges::equal(s, o); }
constexpr void
diff --git a/libstdc++-v3/testsuite/23_containers/inplace_vector/erasure.cc b/libstdc++-v3/testsuite/23_containers/inplace_vector/erasure.cc
index 8fb56e906234..a019dc0a1f15 100644
--- a/libstdc++-v3/testsuite/23_containers/inplace_vector/erasure.cc
+++ b/libstdc++-v3/testsuite/23_containers/inplace_vector/erasure.cc
@@ -1,18 +1,13 @@
// { dg-do run { target c++26 } }
#include <inplace_vector>
+#include <ranges>
#include <testsuite_hooks.h>
-#include <span>
template<typename T, size_t N>
constexpr bool
-eq(const std::inplace_vector<T, N>& l, std::span<const T> r) {
- if (l.size() != r.size())
- return false;
- for (auto i = 0u; i < l.size(); ++i)
- if (l[i] != r[i])
- return false;
- return true;
+eq(const std::inplace_vector<T, N>& l, std::initializer_list<std::type_identity_t<T>> r) {
+ return std::ranges::equal(l, r);
};
constexpr void
diff --git a/libstdc++-v3/testsuite/23_containers/inplace_vector/move.cc b/libstdc++-v3/testsuite/23_containers/inplace_vector/move.cc
index e8703e027fe3..8b5c3e9f247f 100644
--- a/libstdc++-v3/testsuite/23_containers/inplace_vector/move.cc
+++ b/libstdc++-v3/testsuite/23_containers/inplace_vector/move.cc
@@ -177,7 +177,7 @@ static_assert(std::is_nothrow_swappable_v<std::inplace_vector<Z, 0>>);
template<typename T, size_t N>
constexpr bool
-eq(const std::inplace_vector<T, N>& s, std::span<const T> o)
+eq(const std::inplace_vector<T, N>& s, std::initializer_list<std::type_identity_t<T>> o)
{ return std::ranges::equal(s, o); }
constexpr void
diff --git a/libstdc++-v3/testsuite/23_containers/span/init_list_cons.cc b/libstdc++-v3/testsuite/23_containers/span/init_list_cons.cc
deleted file mode 100644
index 1dc30ab1a50b..000000000000
--- a/libstdc++-v3/testsuite/23_containers/span/init_list_cons.cc
+++ /dev/null
@@ -1,65 +0,0 @@
-// { dg-do compile { target c++26 } }
-
-#include <span>
-#include <type_traits>
-
-#if !defined(__cpp_lib_span_initializer_list)
-# error "__cpp_lib_span_initializer_list should be defined"
-#elif __cpp_lib_span_initializer_list < 202311L
-# error "Wrong value for __cpp_lib_span_initializer_list (should be >= 202311L)"
-#endif
-
-// Check the constraint on the initializer_list constructor
-static_assert( std::is_const_v<std::span<const int>::element_type>);
-static_assert(!std::is_const_v<std::span< int>::element_type>);
-
-static_assert( std::is_constructible_v<std::span<const int >, std::initializer_list< int>>);
-static_assert( std::is_constructible_v<std::span<const int >, std::initializer_list<const int>>);
-static_assert( std::is_constructible_v<std::span<const int, 42>, std::initializer_list< int>>);
-static_assert( std::is_constructible_v<std::span<const int, 42>, std::initializer_list<const int>>);
-static_assert(!std::is_constructible_v<std::span< int >, std::initializer_list< int>>);
-static_assert(!std::is_constructible_v<std::span< int >, std::initializer_list<const int>>);
-static_assert(!std::is_constructible_v<std::span< int, 42>, std::initializer_list< int>>);
-static_assert(!std::is_constructible_v<std::span< int, 42>, std::initializer_list<const int>>);
-
-// Check the explicit-ness on the initializer_list constructor
-static_assert( std::is_convertible_v<std::initializer_list< int>, std::span<const int >>);
-static_assert( std::is_convertible_v<std::initializer_list<const int>, std::span<const int >>);
-static_assert(!std::is_convertible_v<std::initializer_list< int>, std::span<const int, 42>>);
-static_assert(!std::is_convertible_v<std::initializer_list<const int>, std::span<const int, 42>>);
-static_assert(!std::is_convertible_v<std::initializer_list< int>, std::span< int >>);
-static_assert(!std::is_convertible_v<std::initializer_list<const int>, std::span< int >>);
-static_assert(!std::is_convertible_v<std::initializer_list< int>, std::span< int, 42>>);
-static_assert(!std::is_convertible_v<std::initializer_list<const int>, std::span< int, 42>>);
-
-constexpr size_t fun1(std::span<const int> s)
-{
- return s.size();
-}
-
-static_assert(fun1({}) == 0);
-static_assert(fun1({1, 2, 3}) == 3);
-static_assert(fun1(std::initializer_list<int>{1, 2, 3}) == 3);
-
-// Stress-test array->pointer decays
-struct decayer {
- constexpr decayer() = default;
- constexpr decayer(decayer *) {}
-};
-
-constexpr size_t fun2(std::span<const decayer> s)
-{
- return s.size();
-}
-
-void test01()
-{
- int intArray[42];
- static_assert(fun1(intArray) == 42);
-
- decayer decArray[42];
- static_assert(fun2(decArray) == 42);
- static_assert(fun2({decArray}) == 1); // decayer[] -> decayer* -> decayer(decayer*) -> init_list<decayer> of 1 element
- static_assert(fun2({decArray, decArray + 42}) == 2); // does not select span(iterator, iterator)
- static_assert(fun2({decArray, decArray, decArray}) == 3);
-}
diff --git a/libstdc++-v3/testsuite/23_containers/span/init_list_cons_neg.cc b/libstdc++-v3/testsuite/23_containers/span/init_list_cons_neg.cc
deleted file mode 100644
index 6b78156ad5df..000000000000
--- a/libstdc++-v3/testsuite/23_containers/span/init_list_cons_neg.cc
+++ /dev/null
@@ -1,36 +0,0 @@
-// { dg-do run { target { c++20 && c++23_down } } }
-// { dg-do compile { target c++26 } }
-
-#include <span>
-#include <utility>
-
-#include <testsuite_hooks.h>
-
-struct Any {
- constexpr Any() { }
- template<typename T> constexpr Any(T) { }
-};
-
-// Examples from P2447R4
-void one(std::pair<int, int>) {}
-void one(std::span<const int>) {}
-void two(std::span<const int, 2>) {}
-constexpr std::size_t three(std::span<void * const> v) { return v.size(); }
-constexpr std::size_t four(std::span<const Any> v) { return v.size(); }
-
-void *array3[10];
-Any array4[10];
-
-int main()
-{
- one({1, 2}); // { dg-error "call of overloaded" "should be ambiguous with the one(std::pair) overload" { target c++26 } }
- two({{1, 2}}); // { dg-error "would use explicit constructor" "should prefer the initializer_list constructor, which is explicit" { target c++26 } }
-
-#if __cpp_lib_span_initializer_list
- static_assert(three({array3, 0}) == 2);
- static_assert(four({array4, array4 + 10}) == 2);
-#else
- static_assert(three({array3, 0}) == 0);
- static_assert(four({array4, array4 + 10}) == 10);
-#endif
-}
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