Parsing arguments in C++ - c++

Question

Firstly, I know my title looks like a commonly asked question, but hear me out. When I say 'Parsing arguments' I don't mean the command line arguments that get passed to the program when it starts up. I'm trying to create a seperate system to receive commands and parse them in runtime.
Main:
int main(int argc, char *args[])
{
cout << "Started up." << endl;
reloop();
}
// Main execution point. Prints text to the console and moves to a void:
void reloop()
{
char *str;
cin >> str;
parseargs(str);
}
// Starts waiting for inputted data, if found, move onto parseargs void.
void parseargs(char *args)
{
char *strings[10];
char delim[] = " ";
int i = 0;
strings[i] = strtok(args,delim);
if(strings[0] == "try")
{
cout << "WORKED!" << endl;
reloop();
}
else
{
cout << "Na. Didn't work." << endl;
reloop();
}
}
// Takes the arguments passed to it, splits them via a space and passes them to an array. From here, compares the first entry in the array to a command. If they equal, output success note.
Now, I'm a C# programmer for quite some time and have only just started C++.. What am I doing wrong? When the program starts up, an error comes up with:
Debug Assertion Failed!
Program: C:\Windows\system32\MSVCP110D.dll
File: c:\program files\microsoft visual studio 11.0\vc\include\istream
Line: 990
Expression: Invalid null pointer
*Note: I do have declarations for each function at the top of the CPP file.

Answer 1

One bug I can find in your code is in function void reloop()
char *str;
cin >> str; <---"Undefined behavior"
You don't allocate memory for str.
correct it either:
char str[SIZE];
Dynamically allocate space: char* str = new char[SIZE];
Next error is:
if(strings[0] == "try")
should be:
if(strcmp( strings[0], "try")!=0)

Answer 2

void reloop() {
char *str; /* WRONG */
cin >> str;
parseargs(str);
}
You should have written it that way :
void reloop() {
char str[BUF_MAX]; /* ok but take care of buffer overflow; maybe use std::string */
cin >> str;
parseargs(str);
}

Answer 3

Even if you know C# please note that you don't know anything about C++ and that even if you're very smart intuition will guide you down the wrong path (actually especially if you're very smart: C++ in quite a few parts is indeed "illogical" so a logic mind is not going to help at all).
The reason is that C++ is the way it is for a mix of complex reasons, including committee effect and a lot of historical heritage. No matter how smart you are you're not going to guess neither history nor what a committee decided.
How char * are part of C++ is one of these things that can only be understood if you know history (especially history of C). The error in you program is that you cannot write
char *str;
cin >> str;
because you didn't allocate the memory for it. It would also be bad code because potentially overflows the memory you allocate. If you're missing this then you're going to miss a LOT of other much more subtle points of C++ programming.
Do yourself a favor and start by reading cover-to-cover a good C++ book instead of just experimenting with a compiler.
Experimenting is not a reasonable path with C++ because of its very complex and sometimes illogical structure and because of "undefined behaviour" that means that when doing a mistake you cannot count on a clear error message but can get crazy behaviour instead (including the most dangerous crazy behaviour... i.e. the code apparently will work anyway even when a mistake is present).

Answer 4

Your code problem has been explained by others.
There is one more general problem with your code: you are not using existing functions or libraries which would do what you need.
Pure C solution:
http://www.gnu.org/software/libc/manual/html_node/Getopt.html
C++ Boost program options:
http://www.boost.org/doc/libs/1_54_0/doc/html/program_options.html