问题
I'm curious about the variable __SIZE_TYPE__ which is predefined by gcc compiler.
Suppose that I coded like following sentence in C
typedef __SIZE_TYPE__ size_t;
Is there any possibility that an error occurs when I use another C compiler excluding gcc?
Do all C compilers have the variable __SIZE_TYPE__?
回答1:
Yes, it is possible that an error occurs as soon as you use any identifier with double underscore. See the C standard 7.1.3:
All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use.
As for __SIZE_TYPE__ that's apparently a gcc identifier. I don't think any other compiler uses it, but there are no guarantees. Another compiler is perfectly free to use the same identifier even for an entirely different purpose.
来源：https://stackoverflow.com/questions/36857141/gcc-compiler-size-type