calloc: 4 bytes in 1 blocks are definitely lost

问题

The following message gets generated after running my program under valgrind:

4 bytes in 1 blocks are definitely lost in loss record 1 of 11
==21938==    at 0x4C2DD10: calloc (vg_replace_malloc.c:623)
==21938==    by 0x401636: main (syntax.c:187)

That's the line of code where the leak was detected:

char *word = calloc(4, sizeof(char));   //syntax.c:187

I'm not understanding what's wrong with the code above. Why is valgrind generating an error?

来源：https://stackoverflow.com/questions/43967592/calloc-4-bytes-in-1-blocks-are-definitely-lost