Comment by Rochus

"Pure" doesn't apply to "language purity" (nobody besides a very few seem to really care about the latter, especially not in C, not even compiler authors), but that nothing else is required than a C89 compatible toolchain to use the library (i.e. it doesn't need any assembler or third-party tools/libraries). See also https://www.merriam-webster.com/dictionary/pure?utm_campaign.... And so far the library compiles with all of my C89 copilers, even the very old ones (and old Posix versions). For a few cases to check, there are notes in the source code.