[SOLVED] container_of:why not "const typeof(*ptr) *__mptr=(ptr);"
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After I figured out every word in the definition,I got another question:
why not replace const typeof( ((type *)0)->member ) *__mptr = (ptr); with "const typeof(*ptr) *__mptr=(ptr);" ?
The second can also check the incompatible initialization and seems more easily to be understood.
This is not an official answer, but that's how I see it. The de-reference for a 'member' will always point to the right field. The way you propose would probably work if you're sure 'member' is always the first field (with no padding at the beginning of the structure), and it may or may not be true depending on the compiler and platform's ABI.
.
and then i found it can not check the initialization like this
Code:
int a;
container_of(a,type,member);
.
but the macro what i mentioned in this thread works.and it made me believe the macro can work everywhere.
thank you for your reminding!i found it could not check the wrong type in this kind of initialization:
Code:
struct dog * pdog;
container_of(&pdog,struct dog,list);
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