[ECOS] Namespace pollution

Bart Veer bartv@ecoscentric.com
Tue Mar 4 15:31:00 GMT 2003

>>>>> "Gary" == Gary D Thomas <gary.thomas@mind.be> writes:

    Gary> Jonathan,
    Gary> I've run into a problem [near and dear to your heart] - a
    Gary> place where the eCos namespace (via include files) intrudes
    Gary> on an application. The problem is in <pthread.h>. This
    Gary> particular application happens to have a typedef for the
    Gary> symbol "destructor", which causes this prototype to fail:

    Gary> // Create a key to identify a location in the thread specific data area.
    Gary> // Each thread has its own distinct thread-specific data area but all are
    Gary> // addressed by the same keys. The destructor function is called whenever a
    Gary> // thread exits and the value associated with the key is non-NULL.
    Gary> externC int pthread_key_create (pthread_key_t *key,
    Gary>                                 void (*destructor) (void *));

    Gary> So, the question(s) are:
    Gary>  * Who's at fault here?  (the application or the kernel)
    Gary>  * How best to solve it?

    Gary> As a work-around, I've modified that particular include file 
    Gary> to avoid this problem (renaming destructor as _destructor).  

    Gary> n.b. This is a portable application from outside the eCos world,
    Gary> so I don't want to have to change it, if possible.  If, on the
    Gary> other hand, this is truly an application issue, I'll gladly take
    Gary> it up with the [application] maintainers.

I believe the "correct" solution is to just remove the argument names
from the header files, i.e. change <pthread.h> to :

     externC int pthread_key_create (pthread_key_t*, void (*)(void*));

Such argument names are not needed in function prototypes, only in the
implementation. They only serve as a form of documentation - and on
occasion that can be very useful.

Another way of tackling the problem involve careful use of underscores
as you have done, e.g.:

     externC int pthread_key_create (pthread_key_t* _key,
                                     void (*_destructor)(void*));

That reduces but does not eliminate the problem. Yet another approach
is to put the argument name in comments:

     externC int pthread_key_create (pthread_key_t* /* key */,
                                     void (* /* destructor */)(void*));

but that is not actually very readable, so much of the documentation
value is lost.

My preferred approach is to leave out the argument name most of the
time, but where has it special documentation value put it in comments.
However I don't guarantee that I have been consistent about this in
all my code.


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