没有动态内存分配的自引用（递归）结构

Question

I have a struct to represent an AST, and I'm on an embedded device, I have no malloc, everything should be either on stack or global.

So my struct;

/* AST Structre */
typedef struct ast {
    uint8_t type; /* This is the token value in grammar.h */

    /* Value of the token */
    union {
        double number;
        char literal;
    } value;

    struct ast *left; /* left hand side of the node */
    struct ast *right; /* right hand side of the node */
} ast_t;

My question is whats the best way to use recursive structs without malloc.

Answer 1

Simply create an array and initialize/assign as needed.

ast_t fred[] = { { 1, {2.0}, NULL,     &fred[1]}, 
                 { 3, {4.0}, &fred[0], NULL    } };

Call the ast_t functions foo(fred); . Be sure to not call free(fred) .