libc VS libspng

Seems unlikely. My spot check of the the two vfprintf implementations shows no flow from one to the other, and shows that part of the Cosmopolitan code has an older lineage than nolibc.

The nolibc source has many reference to copyright held by "Willy Tarreau", under LGPL-2.1 OR MIT license, with a copyright date starting in 2017.

The string "Tarreau" does not exist in the Cosmopolitan library, so that's a strong negative there. Let's look closer.

The file organization is quite different. And so is the implementation. So that's another negative.

Compare the vfprintf in nolibc at https://elixir.bootlin.com/linux/v6.2-rc4/source/tools/inclu... (a 'minimal vfprintf()') with the one in cosmopolitan starting at https://github.com/jart/cosmopolitan/blob/master/libc/stdio/....

Right away we can see nolibc places many functions in the same file while Cosmopolitan uses a one-function-per-filename organization.

Cosmopolitan's fvprintf locks the file (which nolibc doesn't need to do) then calls vfprintf_unlocked which calls __fmt at https://github.com/jart/cosmopolitan/blob/master/libc/fmt/fm... , which is the actual implementation. It look very different from NOLIBC's.

Okay, so perhaps that's they way now but not at the beginning?

We can also go back to Cosmopolitan's original implementation and see how vfprintf goes through https://github.com/jart/cosmopolitan/blob/c91b3c50068224929c... to call "palandprintf", which https://github.com/jart/cosmopolitan/blob/c91b3c50068224929c... says is copyright "Marco Paland" from 2014-2019.

That's a few years older than the start of nolibc, available from https://github.com/mpaland/printf , and part of https://github.com/embeddedartistry/libc , a "libc targeted for embedded systems usage".

Thus, multiple factors seem to agree that nolibc code is not used in the Cosmopolitan library.

libspng is already in LibHunt. I'm surprised there is no comparison with libpng.