Arduino 和指向字符数组的指针

Question

Need to get a pointer to a char array variable.

  char hostName[] = "Server1";
  uint32_t *p;
  p = &hostName;

My understanding is probably lacking seriously, but I cant figure it out. I get the following error on the "p = &hostName;"line.

invalid conversion from 'int*' to 'uint32_t* {aka long unsigned int*}' [-fpermissive]

Can anyone help please.

Answer 1

char hostname[] = "Server1; declares hostName to be an array of char . So &hostname is a pointer to an array of char .

uint32_t *p; defines p to be a pointer to a uint32_t .

A pointer to a an array of char and a pointer to a uint32_t are different things, and they are incompatible types. C does not allow you to assign one to the other.

You can force the conversion using a cast, and the compiler will accept it. But that raises issues about good programming and portability, and you should not do it at this stage of learning C.

To get a pointer to the array, you could use char (*p)[]; p = &hostName; char (*p)[]; p = &hostName; or char (*p)[8]; p = &hostName; char (*p)[8]; p = &hostName; .

However, it is likely you actually want a pointer to the first character in the array, in which case you can use:

char *p;
p = &hostName[0];

Also, when an array is used in an expression, but not as the operand of sizeof or unary & , it is automatically converted to a pointer to its first element, so you can also use:

char *p;
p = hostName;

Answer 2

First of all, from your understanding, if we write the variable with &(ampersand) operator, it will gives the address( that is number). When you print the address, it will be like a unsigned integer.So according to that, You are trying to declare unsigned integer pointer and then assign the address with them.
uint32_t *p; p = &hostName; But this won't makes sense. Because FYI, Pointers are basically store the address of the variables with the same type. p = &hostName This is completely wrong. when doing this, assigns the sequences of character into unsigned integer pointer. Hope this might helps:)