[committed] libstdc++: Fix -Wdeprecated warning about implicit capture of 'this'

[Jonathan Wakely]

Tested x86_64-linux. Pushed to trunk.

-- >8 --

In C++20 it's deprecated for a [=] lambda capture to capture the 'this'
pointer. Using resize_and_overwrite with a lambda seems like overkill to
write three chars to the string anyway. Just resize the string and
overwrite the end of it directly.

libstdc++-v3/ChangeLog:

        * include/experimental/internet (network_v4::to_string()):
        Remove lambda and use of resize_and_overwrite.
---
 libstdc++-v3/include/experimental/internet | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/libstdc++-v3/include/experimental/internet 
b/libstdc++-v3/include/experimental/internet
index f04163dc453..82043c87aca 100644
--- a/libstdc++-v3/include/experimental/internet
+++ b/libstdc++-v3/include/experimental/internet
@@ -1314,20 +1314,12 @@ namespace ip
       {
        auto __str = address().to_string(__a);
        const unsigned __addrlen = __str.length();
-       const unsigned __preflen = prefix_length() >= 10 ? 2 : 1;
-       auto __write = [=](char* __p, size_t __n) {
-         __p[__addrlen] = '/';
-         std::__detail::__to_chars_10_impl(__p + __addrlen + 1, __preflen,
-                                           (unsigned char)prefix_length());
-         return __n;
-       };
-       const unsigned __len = __addrlen + 1 + __preflen;
-#if __cpp_lib_string_resize_and_overwrite
-       __str.resize_and_overwrite(__len, __write);
-#else
-       __str.resize(__len);
-       __write(&__str.front(), __len);
-#endif
+       const unsigned __preflenlen = _M_prefix_len >= 10 ? 2 : 1;
+       __str.resize(__addrlen + 1 + __preflenlen);
+       __str[__addrlen] = '/';
+       std::__detail::__to_chars_10_impl(&__str.front() + __addrlen + 1,
+                                         __preflenlen,
+                                         (unsigned char)_M_prefix_len);
        return __str;
       }
 
-- 
2.43.0