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I'm coming from a windows background so I'm a bit new here, but I'm trying to conditionally use mmap() but only if the platform supports it.

I know now it's a POSIX standard, and I'd like to check for it in my code. However, I'm confused as to the best way to do it.

https://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html

Looking here it says this: CHANGE HISTORY First released in Issue 4, Version 2.

I don't know how to translate to an #if check.

I want to check the POSIX version to make sure its defined and at minimum the version in which mmap is supported.

Google doesn't seem to be much help here.

#if ?????
// code to use mmap()
#endif

That's what I want. Just the ???? part

Thanks in advance.

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    Does this answer your question? How can I determine if the operating system is POSIX in C? i.e. _POSIX_VERSION should be #defined in <unistd.h>. There is also _POSIX_C_SOURCE, to be defined by you in order to ensure symbols for a given version are visible (or, as the case may be, not). Commented Jan 5, 2021 at 17:04
  • aha the second answer unistd.h _POSIX_VERSION thanks. I still don't know which version to check for, but at least I have more information than I started with. I appreciate it. Commented Jan 5, 2021 at 17:06
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