🚀 go-pugleaf

mlg@scr.siemens.com (Michael Greenberg) writes:

>I'm trying to figure out under what circumstances a program can supply
>a definition for a library function.  Is it the case that a program
>cannot supply a definition for any library function except for those
>listed in 17.3.3.4 (new & delete with various signatures)?

That is correct. You cannot extend the "std" namespace, and the names
of the library functions are reserved except as noted.

The reason for the rule is to ensure 3rd-party libraries, and indeed the
implementation-supplied runtime library, can depend on the operation
of the standard functions. If you were allowed to replace them, there
could be no guarantees. (It also allows implementors maximum
freedom in implementing the library, since replacing functions
need not be considered.)

Example: A program used in religious education has a function that
analyzes answers to moral questions via an index and determines the
degree of "sin" involved. If the function were called "sin", that
could create havoc in other parts of the program that attempted to do
trigonometric calculations.

The rule does not mean an implementation must prevent you from
trying to replace library functions. Indeed, it is often
possible to do so for selected functions. You just cannot depend
on being able to do it, particularly in portable code. Such a
program might not compile, might compile but not link, might
link but not run correctly.

>(As an aside, what's the 'C' standard have to say about this?)

No functions in the C library may be replaced. All the names are
reserved.
--
Steve Clamage, stephen.clamage@eng.sun.com
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