“免费”的冲突类型

我收到错误

“免费”的冲突类型

打电话给free()下面的函数。

int main ( )
{
    char fx [] = "x^2+5*x-1";
    node * fxNode = buildTree(fx, sizeof(fx)/sizeof(char));
    printf(deriveFromTree(fxNode)); // Should print "2*x+5"
    free(fxNode);
    return 0;
}

不明白为什么。不确定这是否重要，但上面是什么

#include <stdio.h>

char opstack [5] = {'+','-','*','^', '\0'};

unsigned short int lowerOpPrecedence ( char, char, char * );

int stringToUnsignedInt ( char *, unsigned int * );
int stringToDouble ( char * , double * );
unsigned short int stringCompare ( char * , char * );
void stringCopy ( char * , char * );

typedef struct treeNode
{
    char * fx;
    char * op;
    struct treeNode * gx;
    struct treeNode * hx;
} node;


unsigned short int getNodeState ( node * );
node * buildTree ( char *, int );
char * basicDerivative ( char * );
char * derivateFromTree ( node * );

下面是一堆函数的实现。

你需要添加#include <stdlib.h>提供原型free().

另外，推荐的签名main() is int main (void).