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As confirmed by LWG 2852, the calls to traits_type::compare do not need to be obsvervable, so we can make operator== compare string lengths first and return immediately for non-equal lengths. This avoids doing a slow string comparison for "abc...xyz" == "abc...xy". Previously we only did this optimization for std::char_traits<char>, but we can enable it unconditionally thanks to LWG 2852. For comparisons with a const char* we can call traits_type::length right away to do the same optimization. That strlen call can be folded away for constant arguments, making it very efficient. For the pre-C++20 operator== and operator!= overloads we can swap the order of the arguments to take advantage of the operator== improvements. libstdc++-v3/ChangeLog: PR libstdc++/62187 * include/bits/basic_string.h (operator==): Always compare lengths before checking string contents. [!__cpp_lib_three_way_comparison] (operator==, operator!=): Reorder arguments.
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.