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Diffstat (limited to 'Documentation/nocast-vs-bitwise.md')
| -rw-r--r-- | Documentation/nocast-vs-bitwise.md | 34 |
1 files changed, 18 insertions, 16 deletions
diff --git a/Documentation/nocast-vs-bitwise.md b/Documentation/nocast-vs-bitwise.md index b649abcd..9ba5a789 100644 --- a/Documentation/nocast-vs-bitwise.md +++ b/Documentation/nocast-vs-bitwise.md @@ -1,4 +1,5 @@ -# __nocast vs __bitwise +__nocast vs __bitwise +===================== `__nocast` warns about explicit or implicit casting to different types. HOWEVER, it doesn't consider two 32-bit integers to be different @@ -16,25 +17,26 @@ harder to lose the type by mistake. So the basic rule is: - - `__nocast` on its own tends to be more useful for *big* integers -that still need to act like integers, but you want to make it much -less likely that they get truncated by mistake. So a 64-bit integer -that you don't want to mistakenly/silently be returned as `int`, for -example. But they mix well with random integer types, so you can add -to them etc without using anything special. However, that mixing also -means that the `__nocast` really gets lost fairly easily. - - - `__bitwise` is for *unique types* that cannot be mixed with other -types, and that you'd never want to just use as a random integer (the -integer `0` is special, though, and gets silently accepted - it's -kind of like `NULL` for pointers). So `gfp_t` or the `safe endianness` -types would be `__bitwise`: you can only operate on them by doing -specific operations that know about *that* particular type. +- `__nocast` on its own tends to be more useful for *big* integers + that still need to act like integers, but you want to make it much + less likely that they get truncated by mistake. So a 64-bit integer + that you don't want to mistakenly/silently be returned as `int`, for + example. But they mix well with random integer types, so you can add + to them etc without using anything special. However, that mixing also + means that the `__nocast` really gets lost fairly easily. + +- `__bitwise` is for *unique types* that cannot be mixed with other + types, and that you'd never want to just use as a random integer (the + integer `0` is special, though, and gets silently accepted - it's + kind of like `NULL` for pointers). So `gfp_t` or the `safe endianness` + types would be `__bitwise`: you can only operate on them by doing + specific operations that know about *that* particular type. Generally, you want `__bitwise` if you are looking for type safety. `__nocast` really is pretty weak. -## Reference: +Reference: +---------- * Linus' e-mail about `__nocast` vs `__bitwise`: |