Saturday, March 3, 2012

glibc, an archetypical standard library (vs system calls)

Background -- I was looking for a concrete example of a standard library.

Best example of a standard library is glibc, produced by GNU team. If you strip the G, it's "libc" -- THE C standard library.

"Standard" means this library is a "carpet" hiding all the platform-specific differences and presents a uniform interface to high-level application programmers -- so-called App-Programmer-Interface or "API".

There are many industry standards for this same purpose, such as POSIX, ANSI-C (which standardizes the C programming language + standard lib). Glibc supports all of these standards.

To clarify a common confusion, it's worthwhile to understand this simple example -- glibc functions (like printf) are implemented in platform-specific underlying syscalls.

Exactly What are the platform differences? Short answer -- system calls. Remember System calls call into the "hotel service desk". These syscalls are tied to the processor and the operating system so they are by definition platform-specific. See other posts on syscall vs standard library.

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