c - Valgrind错误: "Invalid read of size 1" due to strstr() with C

Question

Valgrind 输出:

GET /cs3157/tng/index.html
==760== Invalid read of size 1
==760==    at 0x4C2E7D4: strstr (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==760==    by 0x400E67: HandleTCPClient (http-server.c:101)
==760==    by 0x400D42: main (http-server.c:75)
==760==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

相关代码:

FILE *input = fdopen(clntSocket, "r");      //socket wrapped with FILE * 
if (input == NULL)
{
    perror("fdopen failed");
    fclose(input);
    return;
}
char request_buffer[100];
char out_buf[BUF_SIZE];
int len, res;

while( fgets(request_buffer, sizeof(request_buffer),input) != NULL)
{
    request_buffer[sizeof(request_buffer)-1] = '\0';   //null terminates buffer
    char *request = request_buffer;
    char *token_separators = "\t \r\n"; // tab, space, new line
    char *method = strtok(request, token_separators);
    char *requestURI = strtok(NULL, token_separators);
    char *httpVersion = strtok(NULL, token_separators);

    if( strstr(method,"GET") != NULL )
    {
            if( requestURI[strlen(requestURI)] == '/' ) 
                    requestURI = strcat(requestURI,"index.html");
            printf("%s %s\n", method, requestURI);

    } 
    memset(request_buffer,'\0',sizeof(request_buffer) );
}

fclose(input);      //close the socket by closing the FILE * wrapper

我读到此错误通常是由于未能以 null 终止字符串而引起的。我认为 fgets() 之后的第一行可以防止出现问题。我猜我忽略了一些东西。我感谢任何帮助。

编辑:程序因段错误而崩溃。

Answer 1

听起来(来自 Valgrind 的报告)好像 method是 NULL 。您应该使用调试器单步执行此代码，以验证标记化是否按预期工作。

此外，您应该将所有这些指针声明为 const char *因为它们不打算被写入。这当然是一个小问题，但我尝试鼓励使用 const只要有可能。 :)