问题
I am fairly new at C and I don't know the difference between the following two variable declarations:
int* ptr;
int *ptr;
I think that in the declaration int* ptr;, ptr's value cannot be changed whereas it can be changed for the declaration, int *ptr;
I am not sure if that is it though.
What is the concept behind the two declarations?
回答1:
To the compiler, there is no difference between the two declarations.
To the human reader, the former may imply that the "int*" type applies to all declarations in the same statement. However, the * binds only to the following identifier.
For example, both of the following statements declare only one pointer.
int* ptr, foo, bar;
int *ptr, foo, bar;
This statement declares multiple pointers, which prevents using the "int*" spacing.
int *ptr1, *ptr2, *ptr3;
回答2:
Spaces in C are mostly insignificant. There are occasional cases where spaces are important, but these are few and far between. The two examples you posted are equivalent.
回答3:
Like the others said. There is no difference. If you want to understand more complex C type declaration you could find this link userful. Reading C declarations.
回答4:
It's called whitespace operator overloading, see here: http://www2.research.att.com/~bs/whitespace98.pdf
回答5:
int *p;
*p
is no meaning for compiler, (int*) is a type named pointer.
来源：https://stackoverflow.com/questions/7799561/what-is-the-difference-between-int-ptr-and-int-ptr-in-c