Many C programs’ build harnesses are unnecessarily cautious in checking whether various system headers are available, and/or retain checks for headers that passed into obsolescence more than a decade ago. This repository records inventories of all the common, non-system-specific, C system header files available on widely used operating systems.
This project is currently under major revision. You can see results from an older iteration at http://hacks.owlfolio.org/header-survey/, and we have reasonable confidence in some high-level conclusions:
- Except perhaps in deeply-embedded environments, all of C89’s library is universally available.
- Code not intended to run on Windows can also assume most of C99 and much of POSIX. The less-ubiquitous headers from these categories are also the less-useful headers.
- Code that is intended to run on Windows should only use C89
headers and
<stdint.h>. If MSVC 2008 support is required, not even<stdint.h>can be used. (Windows compilers do provide a small handful of POSIX headers, but they do not contain the expected set of declarations!)
Assistance with the aforementioned major revisions would be welcome. Please contact zackw@panix.com if you are interested in helping.