It's also ironic coming from someone who's opening salvo was to describe a post about musl being "non-standard" as constituting a "serious allegation".
Nobody said anything about an absolute definition.
When describing the C standard library, the only reasonable interpretation of "nonstandard" is that it does not adhere to standard C. There are no counter-examples anyone has been able to provide from any corpus.
No, that is your interpretation, and one that, so far as I can tell from all of the responses in this thread, you are alone in believing.
> There are no counter-examples anyone has been able to provide from any corpus.
* https://elinux.org/images/1/15/Anatomy_of_Cross-Compilation_... 2016, see page 14 "de facto standard of Linux C libraries"
* https://www.linuxjournal.com/article/3417 (June 1999) -- "Linux has now standardized on the GNU C library (glibc) as the common implementation for future Linux systems."
* https://www.reddit.com/r/C_Programming/comments/9g6531/where... "For the standard library, uCLibC and muSL are the two lightweight (and thus likely easier to understand) libraries. GLibC ("libc") is more or less the de-facto standard C library for all non-windows (and even some windows) development."
* https://man.archlinux.org/man/glibc.7 -- "For a while, Linux libc was the standard C library in many Linux distributions."
"Standard" is one of those words that can mean different things. Insisting on one absolute definition and calling anyone who uses another definition "disingenuous" is not hugely constructive.