比较strdup函数的返回值和strncmp

Question

I am new to C language. I am trying to compare two returned values from strdup , with the strncmp function, but getting following error:

error: passing argument 2 of 'strncmp' makes pointer from integer without a cast [-Wint-conversion]

my code:

if (0 == strncmp( strdup(str_to_dup1), strdup(str_to_dup2)))

Answer 1

From strncmp

strncmp

int strncmp( const char *lhs, const char *rhs, size_t count );

In you code, you are missing the third argument of strncmp which is the maximum number of character to compare.

Your program is having potential memory leak as the pointer returned by strdup() will be lost after strncmp() call. Also, you should be aware that strdup() can return null pointer if an error occurred.

You should take the strdup() returned pointer to a variable and make sure to check for if some error is occurred and then pass those variables to strncmp() . Once done with strdup() returned pointers, free them using free() .

Answer 2

strncmp takes 3 parameters like below

int strncmp(const char *str1, const char *str2, size_t n)

in your code missing the third parameter, the max number characters to be compared