[committed] libstdc++: Simplify __format::_Sink::_M_reset

[Jonathan Wakely via Gcc-patches]

Tested x86_64-linux. Pushed to trunk.

-- >8 --

Using an offset as the second argument instead of an iterator makes it
easier for callers, as they don't need to create an lvalue span in order
to get an iterator from it for the _M_reset call.

libstdc++-v3/ChangeLog:

        * include/std/format (__format::_Sink::_M_reset): Change second
        argument from iterator to offset.
---
 libstdc++-v3/include/std/format | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index fe2caa58688..128a5b79282 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -2537,11 +2537,10 @@ namespace __format
 
       // Replace the current output range.
       void
-      _M_reset(span<_CharT> __s,
-              typename span<_CharT>::iterator __next) noexcept
+      _M_reset(span<_CharT> __s, size_t __pos = 0) noexcept
       {
        _M_span = __s;
-       _M_next = __next;
+       _M_next = __s.begin() + __pos;
       }
 
       // Called by the iterator for *it++ = c
@@ -2599,7 +2598,7 @@ namespace __format
   // A sink that fills a sequence (e.g. std::string, std::vector, std::deque).
   // Writes to a buffer then appends that to the sequence when it fills up.
   template<typename _Seq>
-    class _Seq_sink : public _Buf_sink<typename _Seq::value_type>
+    class _Seq_sink final : public _Buf_sink<typename _Seq::value_type>
     {
       using _CharT = typename _Seq::value_type;
 
@@ -2610,6 +2609,8 @@ namespace __format
       _M_overflow() override
       {
        auto __s = this->_M_used();
+       if (__s.empty())
+         return;
        if constexpr (__is_specialization_of<_Seq, basic_string>)
          _M_seq.append(__s.data(), __s.size());
        else
@@ -2618,6 +2619,9 @@ namespace __format
       }
 
     public:
+      // TODO: for SSO string, use SSO buffer as initial span, then switch
+      // to _M_buf if it overflows? Or even do that for all unused capacity?
+
       [[__gnu__::__always_inline__]]
       _Seq_sink() noexcept(is_nothrow_default_constructible_v<_Seq>)
       { }
@@ -2722,21 +2726,20 @@ namespace __format
          return; // No need to switch to internal buffer yet.
 
        auto __s = this->_M_used();
-       _M_count += __s.size();
 
        if (_M_max >= 0)
          {
+           _M_count += __s.size();
            // Span was already sized for the maximum character count,
            // if it overflows then any further output must go to the
            // internal buffer, to be discarded.
-           span<_CharT> __buf{_M_buf};
-           this->_M_reset(__buf, __buf.begin());
+           this->_M_reset(this->_M_buf);
          }
        else
          {
            // No maximum character count. Just extend the span to allow
            // writing more characters to it.
-           this->_M_reset({__s.data(), __s.size() + 1024}, __s.end());
+           this->_M_reset({__s.data(), __s.size() + 1024}, __s.size());
          }
       }
 
@@ -3473,6 +3476,7 @@ namespace __format
 
   template<typename _Context>
     template<typename... _Args>
+      inline
       basic_format_args<_Context>::
       basic_format_args(const _Store<_Args...>& __store) noexcept
       {
@@ -4063,7 +4067,7 @@ namespace __format
 {
 #if 1
   template<typename _CharT>
-    class _Counting_sink : public _Iter_sink<_CharT, _CharT*>
+    class _Counting_sink final : public _Iter_sink<_CharT, _CharT*>
     {
     public:
       _Counting_sink() : _Iter_sink<_CharT, _CharT*>(nullptr, 0) { }
-- 
2.41.0