Read this: https://docs.codewars.com/training/troubleshooting
I write the code it says undefined but when I write it on codepen, the result is true. I can not understand it.
I found the mistake, it should be return String, not print(String)
This comment is hidden because it contains spoiler information about the solution
It's not solution) but it works).
Good for you, don't post solutions in Discourse.
The description says it has one parameter but in C it has two parameters as one is convenient preallocated memory for the result.
A little confusing.
return newStr not print(newStr)
Not a kata issue (or maybe it was too, but this solution doesn't pass the basic tests now). The result should be written to *dst, not to new malloced memory.