Segmentation fault, no matter on how i change the code C++ [closed] - c++

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this is my code
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <cstring>
#include <iostream>
using namespace std;
bool endsWith(string const &value, string const &ending)
{
if(value.length() >= ending.length())
{
return (value.compare(value.length() - ending.length(), ending.length(), ending) == 0);
}
return false;
}
void listdir(const char *directory, const char *extension)
{
DIR *dir;
struct dirent *entry;
if(!(dir = opendir(directory)))
{
return;
}
while(entry = readdir(dir))
{
if(entry->d_type == DT_DIR)
{
char path[1024];
int len = snprintf(path, sizeof(path)-1, "%s/%s", directory, entry->d_name);
path[len] = 0;
if(strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0)
{
listdir(path, extension);
}
}
else
{
string file = entry->d_name;
if(endsWith(file, strcat((char *) ".", extension)) || extension == "*")
{
printf("%s \n", entry->d_name);
}
}
}
closedir(dir);
}
int main(int count, char *parameters[])
{
const char *type = "*";
const char *path = ".";
if(count > 1)
{
path = parameters[1];
}
if(count > 2)
{
type = parameters[2];
}
if(count < 1 || count > 3)
{
return 0;
}
listdir(path, type);
return 0;
}
And no matter, what i am doing, i always receive segmentation fault.
Compiling it with g++ under debian is no problem, but running the application puts out always "Segmentation fault"
So what's the matter?

Answer 1

Your error lies in the line strcat((char *) ".", extension), where you try to write data to the memory underlying a string literal.
String literals are loaded into a read only memory segment and trying to write to that causes your segfault.
If you wish to use strcat, you have to provide a target buffer of sufficient size (which is not checked, so using strncat is often preferred). Since this size is undetermined at compile time, you are forced to compute the length of the two strings you wish to append to one another and allocate a buffer of sufficient size with new or malloc.
However, the easiest way of performing a string concatenation in C++ is to forget all about the C equivalents and simply use ::std::string like so:
::std::string s = "hello ";
s += "world";