[C++] Logic Error (std::logic_error)

[dodle]

My program compiles fine but a logic error (http://en.cppreference.com/w/cpp/error/logic_error) is thrown if I invoke it without any arguments. Otherwise it works fine.

Code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#include <cstdlib>

void ShowUsage(char* me)
{
cout << "\n\tUsage:\t" << (string)me << " <infile> <outfile>\n\n";
}

int main(int argc, char** argv)
{
char me[] = "blah";

if (argc > 3)
{
cerr << "\nToo many arguments\n";
ShowUsage(me);
return 1;
}

if ((string)argv[1] == "--help" or (string)argv[1] == "-h")
{
ShowUsage(me);
return 0;
}

if (argc < 3)
{
cerr << "\nNot enough arguments\n";
ShowUsage(me);
return 1;
}

return 0;
}

Output:

$ ./test
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_S_construct NULL not valid
Aborted

I can't seem to see where the problem is.


----- SOLVED -----

Oh! Caught it. It's this line:

if ((string)argv[1] == "--help" or (string)argv[1] == "-h")

There is no argv[1].


----- EDIT -----

New code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#include <cstdlib>

void ShowUsage(char* me)
{
cout << "\n\tUsage:\t" << (string)me << " <infile> <outfile>\n\n";
}

int main(int argc, char** argv)
{
char me[] = "blah";

if (argc > 3)
{
cerr << "\nToo many arguments\n";
ShowUsage(me);
return 1;
}

if (argc < 3)
{
if (argc == 2 && ((string)argv[1] == "--help" or (string)argv[1] == "-h"))
{
ShowUsage(me);
return 0;
}
else
{
cerr << "\nNot enough arguments\n";
ShowUsage(me);
return 1;
}
}

return 0;
}

[the_unforgiven]

My program compiles fine but a logic error (http://en.cppreference.com/w/cpp/error/logic_error) is thrown if I invoke it without any arguments. Otherwise it works fine.

Code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#include <cstdlib>

void ShowUsage(char* me)
{
cout << "\n\tUsage:\t" << (string)me << " <infile> <outfile>\n\n";
}

int main(int argc, char** argv)
{
char me[] = "blah";

if (argc > 3)
{
cerr << "\nToo many arguments\n";
ShowUsage(me);
return 1;
}

if ((string)argv[1] == "--help" or (string)argv[1] == "-h")
{
ShowUsage(me);
return 0;
}

if (argc < 3)
{
cerr << "\nNot enough arguments\n";
ShowUsage(me);
return 1;
}

return 0;
}

Output:

$ ./test
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_S_construct NULL not valid
Aborted

I can't seem to see where the problem is.


----- SOLVED -----

Oh! Caught it. It's this line:

if ((string)argv[1] == "--help" or (string)argv[1] == "-h")

There is no argv[1].

More like, argv[1] is NULL at that point and string constructor fails when passed a NULL. :)