As DR

Author: H-G-Hristov

libcxx/include/istream

@@ -294,13 +294,11 @@ public:
   basic_istream& getline(char_type* __s, streamsize __n, char_type __dlm);
 
   basic_istream& ignore(streamsize __n = 1, int_type __dlm = traits_type::eof());
-#    if _LIBCPP_STD_VER >= 26
-  _LIBCPP_HIDE_FROM_ABI basic_istream& ignore(streamsize __n, char_type __delim)
-    requires is_same_v<char_type, char>
-  {
-    return this->ignore(__n, _Traits::to_int_type(__delim));
+  template <class _Tp = char_type>
+  inline _LIBCPP_HIDE_FROM_ABI_AFTER_V1 typename std::enable_if<is_same<_Tp, char>::value, basic_istream&>::type
+  ignore(streamsize __n, char_type __delim) {
+    return ignore(__n, traits_type::to_int_type(__delim));
   }
-#    endif
   int_type peek();
   basic_istream& read(char_type* __s, streamsize __n);
   streamsize readsome(char_type* __s, streamsize __n);

libcxx/test/std/input.output/iostream.format/input.streams/istream.unformatted/ignore.char_type.pass.cpp

@@ -6,8 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// REQUIRES: std-at-least-c++26
-
 // Requires 396145d in the built library.
 // XFAIL: using-built-library-before-llvm-9
 
@@ -33,5 +31,10 @@ int main(int, char**) {
   in >> str;
   assert(str == "Clown");
 
+  // Parameter value "-1L" doesn't cause ambiguity with the char_type overload.
+  in.ignore(100, -1L); // ignore up to EOF, which is the default behavior
+  assert(in.eof()); // stream should be at EOF now
+  // assert(in.gcount() == 5);
+
   return 0;
 }