Le 2011-11-12 à 17:13:00, Claude Heiland-Allen a écrit :
A nice idiom for malloc is to use the sizeof of the target of the
pointer to which you are assigning its result (no explicit cast needed
when assigning from a void * afaik, at least no warnings/errors here
with gcc (Debian 4.4.5-8) 4.4.5):
struct foo *f = malloc(sizeof(*f));
1. This does not work in C++ because implicit casts from void* are all
assumed to be mistakes ;
2. In any case, this requires that you did type f in the malloc. The
problem we have here is because the wrong type name was typed in a sizeof.
If a wrong type name can be typed there, so can a wrong variable name.
Therefore, either use «operator new», or if you're stuck with C, use a
macro that does the job for you :
#define NEW(T) ((T*)malloc(sizeof(T)))
so that if you do a wrong assignment, you will get an error for it :
struct foo *e = NEW(foo);
struct foo *f = NEW(typeof(*f));
struct bar *g = NEW(foo); // wrong
struct bar *h = NEW(typeof(*f)); // wrong
error: cannot convert ‘foo*’ to ‘bar*’ in initialization
error: cannot convert ‘foo*’ to ‘bar*’ in initialization
But anyway, those mallocs in [fux_kinect] are superfluous because you can
reserve that amount of RAM directly in fux_kinect by removing the «*».
That goes for nearly any struct that you need to create at the same time
as another struct, and destroy at the same time as that same struct, and
never need to change the size of. In order to do that, you need to be able
to init and finalise separately from malloc/free. That's why the function
is named pthread_cond_init and not pthread_cond_new, for example.
______________________________________________________________________
| Mathieu BOUCHARD ----- téléphone : +1.514.383.3801 ----- Montréal, QC
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