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What's the difference between these two declarations?
C Interview Questions and Answers
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What's the difference between these two declarations?
Q: What's the difference between these two declarations?
struct x1 { ... };
typedef struct { ... } x2;
A: The first form declares a structure tag; the second declares a typedef. The main difference is that the second declaration is of a slightly more abstract type--its users don't necessarily know that it is a structure, and the keyword struct is not used when declaring instances of it:
x2 b;
Structures declared with tags, on the other hand, must be defined with the
struct x1 a;
form.
(It's also possible to play it both ways:
typedef struct x3 { ... } x3;
It's legal, if potentially obscure, to use the same name for both the tag and the typedef, since they live in separate namespaces.
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