c - 警告——赋值使指针来自整数而不进行强制转换

Question

我知道这个问题经常被问到，但我读了十几个问题，但仍然没有找到解决方案。编译时我收到警告:

warning: assignment makes pointer from integer without a cast

此警告引用的代码是:

unsigned char *WebPrintReturnLine(BIO *bio) {

long int i;
unsigned int turn = 0;
unsigned char *ptr = 0;
int size;
unsigned char buffer[4096];

i = (long int) WebRead(bio, buffer, sizeof(buffer));
if( (ptr = (unsigned char *) malloc(strlen(buffer))) == 0 ) {
    printf("Error: Couldn't allocate memory in WebPrintReturnLine\n");
    return ptr;
}

//strlen does not care about '\0' but as array begin at 0 it nulifies
size = strlen(buffer);
//strcpy the buffer into the allocated memory
strcpy(ptr, buffer);
printf("%d\n", isend(buffer, sizeof(buffer)));

while( (i > 0) && (!isend(buffer, sizeof(buffer))) ) {
    i = (long int) WebRead(bio, buffer, sizeof(buffer));
    size += strlen(buffer);
    if( (ptr = (unsigned char*) realloc(ptr, size)) == 0 ) {
        printf("Error: Couldn't reallocate memory in WebPrintReturnLine\n");
        ptr = 0;
        return ptr; 
    }//End if
    //Strcat the original string and the buffer together
    strcat(ptr, buffer);
}//End while

//Now finally print the line
printf("%s", ptr);

return ptr;
}

这被调用了:

unsigned char *ptr;    
if( (ptr = WebPrintReturnLine(bio)) == 0 )
    return -1;

我首先想在这个问题中缩短该代码，但我担心我可能会监督导致此警告的某些内容。

Answer 1

因此警告位于您问题中的第二个代码片段上。 WebPrintReturnLine 的声明在调用时不可见。根据 C90 规则，编译器假定它返回 int (在本例中是错误的)。根据C99规则，该调用是非法的。您需要为声明 WebPrintReturnLine 的 header 添加 #include。 ——基思·汤普森