Add C11 error checking to vsnprintf()

[saxbophone]

C11 specifies that vsnprintf() is to check for the following conditions:

• output buffer or format string are null pointers
• buffer size is zero

C11 also specifies "constraint handler functions" that may be set, but that's far more involved, and having at least some error-handling for bad arguments like these is probably quite useful.

Source: https://en.cppreference.com/w/c/io/vfprintf#:~:text=5%2D8),constraint%20handler%20function%3A

I know the C library provided here doesn't specify C99 or C11 (although the former is implied due to the presence of functions like vsnprintf() and friends), but this seems like a useful and important error case to check.

Let me know what you think

[spicyjpeg]

Looks fine. I've been waiting to release v0.23 due to several bugs that made their way into the GPU command queue implementation, but I can just merge this in once I manage to fix those. Thank you.

[saxbophone]

Looks fine. I've been waiting to release v0.23 due to several bugs that made their way into the GPU command queue implementation, but I can just merge this in once I manage to fix those. Thank you.

You're welcome!

I noticed in the libc readme, that invitations for further contributions for missing functions in libc are welcome. When I have the time (I don't currently! 😢), I might make a list of all the C stdlib functions and tick off the ones that the SDK's libc currently includes.

[saxbophone]

Thank you!