C++ segmentation fault with strcpy

[the_real_fourthdimension]

Hey All

I've got this code that's causing a segmentation fault:


name = "alphaUpper" + length; // length is a previously defined string
char wName1[name.length()];
strcpy (wName1, name.c_str());

This is my first time working with strcpy in C++, so if anyone has any insight as to what I'm doing that's causing the segmentation fault, I'd really appreciate it.
Thanks.

[eye208]

name.length() does not include the string delimiter. strcpy() will cause a buffer overflow on the stack, possibly overwriting the function's return address and causing the segfault.

[the_real_fourthdimension]

name.length() does not include the string delimiter. strcpy() will cause a buffer overflow on the stack, possibly overwriting the function's return address and causing the segfault.

Thanks. I thought it might be something like that, so I changed the code to this, but I'm still having issues:


char * wName;
name = "alphaLower" + length;
wName = new char[name.size() + 1];
strcpy (wName, name.c_str());

Thanks again.

[dwhitney67]

Declaring the size of an array during runtime is against ISO C++ programming standards. If you compile with the -pedantic compiler flag you will see something similar to the following:


g++ -Wall -ansi -pedantic test.cpp
...
test.cpp:6: error: ISO C++ forbids variable length array ‘array’


Aside from that "little" issue, why is it that you require a C-style char array??

If you attempt something similar to the following, then you should have no problems:


#include <string>
#include <cstring>

int main()
{
std::string foo("foo");
char* array = new char[foo.length() + 1];
strcpy(array, foo.c_str());
// ...
delete [] array;
}

But the question still lingers; why do you need a C-style string? Why not just declare another std::string?

[Npl]

Thanks. I thought it might be something like that, so I changed the code to this, but I'm still having issues:


char * wName;
name = "alphaLower" + length;
wName = new char[name.size() + 1];
strcpy (wName, name.c_str());

Thanks again.
There is an own Method for copying strings to char-arrays. Should be your prefered way of doing it.

char * wName;
name = "alphaLower" + length;
wName = new char[name.size() + 1];
name.copy(wName, string::npos);
wName[name.size()] = '0';