当字符串相等时，strcmp结果为false

Question

This is my code:

        if(strcmp(pch,map[i].name)==0){
            printf("Equal\n");
            return 0;
        }

pch is read from a file, map[i].name has a known size of 64. This works great for strings smaller than 64. when comparing these two strings below of size 63:

file11111111111111111111111111111111111111111111111111111111111 and

file11111111111111111111111111111111111111111111111111111111111

everything is peachy and the result as expected is equal, but when these two (of size 64) are compared:

file111111111111111111111111111111111111111111111111111111111111 and

file111111111111111111111111111111111111111111111111111111111111

the return is false. I thought of doing:

        if(strncmp(pch,map[i].name,64)==0){
            printf("Equal\n");
            return 0;
        }

And it does work for strings of exact size of 64, but for strings that are smaller the result is random. What kind of quirkiness am i dealing with here?

EDIT: this is the full code:

    char * pch;
    char tempFilesNeeded[100*64+100];
    strcpy(tempFilesNeeded,map[i].filesNeeded);
    pch = strtok(tempFilesNeeded,",");
    while (pch != NULL)
    {
        if(strcmp(pch,map[i].name)==0){
            printf("Equal\n");
            return 0;
        }

        pch = strtok (NULL, ",");
    }

Answer 1

Well, if it's

char pch[64];

then you can't have 64 visible characters in there, since the last entry is needed for the termination. If you do have "file111111111111111111111111111111111111111111111111111111111111" in that array, it's not terminated and calling strcmp() on it invokes undefined behavior.

Also, as a minor point, saying that strcmp() returns "false" is wrong, since its return is not boolean. It returns the relation between the two first differing characters; if no characters differ the strings are equal, then it returns zero.

Answer 2

如果一个或两个数组的确切大小为64，则您将缺少最后一个'\\ 0'字符串结尾。