Return a copy of the internally buffered sequence of characters maintained by this stream object in a basic_string that uses the specified allocator.
Declared in <bslstl_ostringstream.h>
template<class SALLOC>
basic_string<CHAR_TYPE, CHAR_TRAITS, SALLOC>
str(SALLOC const& allocator) const
requires bsl::IsStdAllocator<SALLOC>::value;