Could strncat or strcpy cause a loop to continue to the next iteration?

Question

I have a the following code in a for loop. I am trying to copy a string into a char**. However, when I run the below code, I never get to the "HERE" portion of my code. Instead, the next iteration of the for loop is executed. Can anyone explain this behavior?

string str = "ls -1";
string cmd = "ls";
char** command;

command = new char*[str.size()+1];

strncat(*command, str.c_str(), str.size+1); 
cout << "HERE\n";

*command = strtok(*command, " ");

execvp(cmd.c_str(), command);

EDIT:

I am using a char** to fit the parameters of execvp, and to use strtok to separate on spaces.

There is likely a problem with flushing `cout`. Replace \n with `std::endl` to force a flush. See [this answer](http://stackoverflow.com/a/22345401/7359094). — François Andrieux, Feb 27 '17 at 19:31
You're newing an array of pointers-to-char, those pointers aren't being set to point at any actual character buffers, so you can't just start using strncat on them. You would be better off using strings and vectors, which are harder to screw up. — Tony Delroy, Feb 27 '17 at 19:33
Thank you @BoPersson! Forgetting to allocate memory to the pointers was the problem. — ThanksInAdvance, Feb 27 '17 at 19:56
There is no for loop in this code, so it's impossible to say what it may or may not be doing. — Pete Becker, Feb 27 '17 at 19:56

score 0 · Answer 1 · answered Feb 27 '17 at 19:39

0

too may pointers

char** command;
command = new char*[str.size()+1]

should be

char* command;
command = new char[str.size()+1]

Or better, stop mixing c++ string and c style 'strings'.

answered Feb 27 '17 at 19:39

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Could strncat or strcpy cause a loop to continue to the next iteration?

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