fix(io): correct write_all_nullptr_case and prevent FD leak in POSIX pipe setup (#1201)

- freestanding/io_buffer/output.h: fix write_all_nullptr_case to dispatch to
  scatter_write_all(_bytes)_decay on the output stream (optstm), and keep
  buffer_curr consistent.
- hosted/platforms/posix.h: avoid FD leaks in the POSIX pipe constructor by
  wrapping FDs with posix_file_factory and setting FD_CLOEXEC; transfer
  ownership explicitly and keep a single assignment point.

No API changes. Success paths unchanged. Rebase-only history preserved.

Author: mq-loser

include/fast_io_freestanding_impl/io_buffer/output.h

@@ -122,14 +122,30 @@ inline constexpr char_type const *write_some_overflow_impl(optstmtype optstm,
 }
 
 template <::std::integral char_type, typename optstmtype>
-inline constexpr void write_all_nullptr_case(basic_io_buffer_pointers<char_type> &__restrict pointers,
+inline constexpr void write_all_nullptr_case(optstmtype optstm, basic_io_buffer_pointers<char_type> &__restrict pointers,
 											 char_type const *first, char_type const *last)
 {
-	basic_io_scatter_t<char_type> const scatters[2]{
-		{(pointers.buffer_begin ? pointers.buffer_begin : first),
-		 static_cast<::std::size_t>(pointers.buffer_curr - pointers.buffer_begin)},
-		{first, static_cast<::std::size_t>(last - first)}};
-	::fast_io::operations::decay::scatter_write_all_decay(pointers, scatters, 2);
+	if constexpr (::fast_io::operations::decay::defines::has_any_of_write_bytes_operations<optstmtype>)
+	{
+		io_scatter_t const scatters[2]{
+			{reinterpret_cast<::std::byte const *>(pointers.buffer_begin ? pointers.buffer_begin : first),
+			 static_cast<::std::size_t>(pointers.buffer_begin
+											? (reinterpret_cast<::std::byte const *>(pointers.buffer_curr) -
+											   reinterpret_cast<::std::byte const *>(pointers.buffer_begin))
+											: 0u)},
+			{reinterpret_cast<::std::byte const *>(first),
+			 static_cast<::std::size_t>(reinterpret_cast<::std::byte const *>(last) -
+										 reinterpret_cast<::std::byte const *>(first))}};
+		::fast_io::operations::decay::scatter_write_all_bytes_decay(optstm, scatters, 2);
+	}
+	else
+	{
+		basic_io_scatter_t<char_type> const scatters[2]{
+			{(pointers.buffer_begin ? pointers.buffer_begin : first),
+			 static_cast<::std::size_t>(pointers.buffer_begin ? (pointers.buffer_curr - pointers.buffer_begin) : 0u)},
+			{first, static_cast<::std::size_t>(last - first)}};
+		::fast_io::operations::decay::scatter_write_all_decay(optstm, scatters, 2);
+	}
 	pointers.buffer_curr = pointers.buffer_begin;
 }
 

include/fast_io_hosted/platforms/posix.h

@@ -1415,14 +1415,25 @@ class basic_posix_family_pipe
 		int a2[2]{-1, -1};
 #if (defined(_WIN32) && !defined(__WINE__) && !defined(__BIONIC__)) && !defined(__CYGWIN__)
 		if (noexcept_call(::_pipe, a2, 131072u, _O_BINARY) == -1)
+			throw_posix_error();
 #elif defined(__linux__)
 		if (noexcept_call(::pipe2, a2, O_CLOEXEC) == -1)
+			throw_posix_error();
 #elif (defined(__MSDOS__) || defined(__DJGPP__)) || defined(__NEWLIB__)
 		if (noexcept_call(::pipe, a2) == -1)
+			throw_posix_error();
 #else
-		if (noexcept_call(::pipe, a2) == -1 || ::fast_io::details::sys_fcntl(a2[0], F_SETFD, FD_CLOEXEC) == -1 || ::fast_io::details::sys_fcntl(a2[1], F_SETFD, FD_CLOEXEC) == -1)
+		{
+			if (noexcept_call(::pipe, a2) == -1)
+				throw_posix_error();
+			::fast_io::posix_file_factory fd0(a2[0]);
+			::fast_io::posix_file_factory fd1(a2[1]);
+			::fast_io::details::sys_fcntl(fd0.fd, F_SETFD, FD_CLOEXEC);
+			::fast_io::details::sys_fcntl(fd1.fd, F_SETFD, FD_CLOEXEC);
+			fd0.fd = -1;
+			fd1.fd = -1;
+		}
 #endif
-			throw_posix_error();
 		pipes->fd = *a2;
 		pipes[1].fd = a2[1];
 #endif