Is __int32 defined?

Question

gcc c89

I am came across this code.

typedef __int32 int32_t;
typedef unsigned __int32 uint32_t;
typedef __int64 int64_t;
typedef unsigned __int32 uint64_t;

I am just wondering that is the __int32 I didn't think that was a type? Why the underscore?

Does this mean I could do things like this?

typedef __int32 myInt32;

Many thanks for any advice,

Answer 1

The type is not standard, but is supported on your compiler.

Symbols that begin with an underscore or contain two underscores are reserved by the standard for your compiler's implementation.

See Why do people use __(double underscore) so much in C++ (The question is about C++ but the reason is the same)