指针ABC。 错误：一元'*'的类型参数无效（具有'struct config'）

Question

I have a basic problem. I should know enough about pointers by now. The way I see it configData is the first link in a linked list (of the type struct config) while procNames is a pointer to the first link in a linked list of the type struct config. So if I want to say that procNames is equal to configData then I need to access the pointer that points to configData which is *configData . Anyhow I think I am missing something. Anyone sees the problem? Also, I get the next error: error: invalid type argument of unary '*' (have 'struct config')

struct config_line {
    char name[MAX_WORD];
    int time;
};

struct config {
    struct config_line *lines;
    int count;
};

//global variable
struct config configData;
//local variable
struct config *procNames;
//the problem (done locally) 
procNames = *configData;

Answer 1

I think you want

procNames = &configData;

This sets the pointer procNames to the address of the structure configData .

You can access the elements using either

procNames->count
procNames->lines[i].name  // Pointer to the 1st char of the name in the i'th config_line structure

or

configData.count
configData.lines[i].name

Remember that, since lines is itself a pointer, you'll need to allocate memory for each config_line structure:

struct config_line thisLine;   // Declare a structure
procNames->lines = &thisLine;  // Point to it

or

// Declare a pointer to an array of structures, allocate memory for the structures
struct config_line *linePtr = malloc(NUM_STRUCTS * sizeof(struct config_line));
procName->lines[i] = *linePtr; // Points to 1st structure in the array

Answer 2

Based on your description of what you are trying to do, you need to take the address of configData (write &configData on the last line). What you are trying to do on the last line is dereference configData, which the compiler will not let you do since configData is not a pointer (it does not store an address inside).

The error message is fairly clear on this. Unary * takes a single pointer as an argument, but the argument used of type struct config, and not a pointer.