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iOS __typeof typeof

2016-04-01 09:44 357 查看
As others have mentioned,
typeof()
is an extension of C that has various support in respective compilers.
If you happen to be writing Objective-C for iOS or Mac apps, chances are good that you will be compiling your app with the Clang compiler.

Clang does support the use of
typeof()
, but technically it's for when your C Language Dialect is set to be a gnu* type. However
__typeof__()
is supported in both c* and gnu* language dialects - as detailed in the Clang documentation.

Now if you're writing your code with Xcode, the default setting for the C language dialect appears to be GNU99 and the option of allowing 'asm' 'inline' 'typeof' is set to Yes, so using
typeof()
won't bring you any problems.



If you want to be (arguably) safer when using the Clang compiler, use
__typeof__()
. This way you won't be affected if the C Language Dialect being used for compilation changes or if someone decides to turn off the allowance of 'typeof'.
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