Re: libc headers

[John Hasler <jhasler@debian.org>]

Daniel McBrearty writes:
> I am trying to compile some code that uses a function __select. The
> compiler complains that the function is not declared. This fucntion turns
> out to be part of libc.so.6 library I think.

That name is internal to the library.  From the libc info doc:

  In addition to the names documented in this manual, reserved names
  include all external identifiers (global functions and variables) that
  begin with an underscore (`_') and all identifiers regardless of use that
  begin with either two underscores or an underscore followed by a capital
  letter are reserved names.  This is so that the library and header files
  can define functions, variables, and macros for internal purposes without
  risk of conflict with names in user programs.

It is a serious error to rely on such functions.  They are intended _only_
for the internal use of the library.  They may disappear or change their
semantics without warning between minor versions.  Any program that relies
on them is buggy.
-- 
John Hasler