Note that using memset() is better reserved to initialise variable-size
structures or buffers. Even if memset() is extremely optimised,
it is still not as fast as not doing anything.
read_events(...) {
struct io_event ent;
memset(&ent, 0, sizeof(ent));
while (...) {
aio_read_evt(ctx, &ent);
}
...
}
Should be written (when "ent" has to be cleared):
read_events(...) {
struct io_event ent = {};
while (...) {
aio_read_evt(ctx, &ent);
}
...
}
Just compare the code generated by (using GCC):
struct io_event ent;
memset(&ent, 0, sizeof(ent));
ent.data = 0;
if (ent.obj != 0) printf ("bad");
And:
struct io_event ent = {};
ent.data = 0;
if (ent.obj != 0) printf ("bad");
and that is even without speaking of complete variable elimination
when the structure is not used, unknown pointer alignement when
memset function is not inlined, or aliasing optimisation.
Etienne.
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This archive was generated by hypermail 2b29 : Tue Jul 15 2003 - 22:00:34 EST