Run Check Failure #2

[goth_nerd]

Hi Guys

Is there anyone around who is good with C++?
I keep getting an error when trying to copy a char array to a char pointer e.g

strncpy_s(buffer, sizeof(temp), temp, _TRUNCATE);

I get a "Stack around the variable 'temp' was corrupted"

Please let me know if more information is needed.

P.S: The subject is meant to say RunTime Check Failure #2

 

[Mr.Jax]

Show me all the code.
eg. declaration and init of buffer, temp and _TRUNCATE.

 

[Ancalagon]

Isn't the sizeof parameter supposed to be the number of bytes?

In which case, it would be the size of a char multiplied by the length of temp.

 

[goth_nerd]

void fixupstr(char * buffer)
{
	char     temp[1024] = { 0 };
	char *   pos = buffer;
	char *   destpos = temp;
	char     lastchar = 0;

	while (*pos != 0)
	{
		if (((*pos == '{') ||
			(*pos == '}') ||
			(*pos == ';') ||
			(*pos == ',') ||
			(*pos == '=')) && (lastchar != ' ') || (lastchar == ',') || (lastchar == '='))
		{
			*destpos++ = ' ';
			*destpos++ = *pos;
		}
		else
		{
			*destpos++ = *pos;
		}
		lastchar = *pos++;
	}
	*destpos = 0;
	if (*(destpos - 1) == '\n')
	{
		*(destpos - 2) = 0;
	}
	
	strncpy_s(buffer, sizeof(buffer), temp, _TRUNCATE);
}

int main()
{
      char buffer[1024] = {0};
      fgets(buffer, sizeof(buffer), *inFile); //inFile is the input file
      fixupstr(buffer);
}

 

[goth_nerd]

Show me all the code.
eg. declaration and init of buffer, temp and _TRUNCATE.

Hi I just posted the code.

 

[cguy]

BTW, sizeof(buffer) in fixupstr will be 8 (well, pointer size) not 1024.

To debug, you may want to verify that (destpos - temp) is less than 1024 (buffer overflow can cause stack corruption that isn't detected immediately).

 

[goth_nerd]

BTW, sizeof(buffer) in fixupstr will be 8 (well, pointer size) not 1024.

To debug, you may want to verify that (destpos - temp) is less than 1024 (buffer overflow can cause stack corruption that isn't detected immediately).

I just checked and it is less than 1024.

 

[Ancalagon]

What runtime library are you using? Microsoft Visual C++?

The definitions that I can find for the strncpy_s function have the destination first and then the source. So, you should swap your parameters around.

 

[goth_nerd]

What runtime library are you using? Microsoft Visual C++?

The definitions that I can find for the strncpy_s function have the destination first and then the source. So, you should swap your parameters around.

I am using MS Visual C++. But buffer is my destination and temp is my source.

 

[Mr.Jax]

void fixupstr(char * buffer)
{
	char     temp[1024] = { 0 };
	char *   pos = buffer;
	char *   destpos = temp;
	char     lastchar = 0;

	while (*pos != 0)
	{
		if (((*pos == '{') ||
			(*pos == '}') ||
			(*pos == ';') ||
			(*pos == ',') ||
			(*pos == '=')) && (lastchar != ' ') || (lastchar == ',') || (lastchar == '='))
		{
			*destpos++ = ' ';
			*destpos++ = *pos;
		}
		else
		{
			*destpos++ = *pos;
		}
		lastchar = *pos++;
	}
	*destpos = 0;
	if (*(destpos - 1) == '\n')
	{
		*(destpos - 2) = 0;
	}
	
	strncpy_s(buffer, sizeof(buffer), temp, _TRUNCATE);
}

int main()
{
      char buffer[1024] = {0};
      fgets(buffer, sizeof(buffer), *inFile); //inFile is the input file
      fixupstr(buffer);
}

- Since you're adding a space when you encounter that set of chars, temp should be at least double the size of buffer. But you're copying back to buffer, so....buffer should be 2x its allowed content size really.
- strmcpy_s: sizeof(buffer) is going to be 4(32bit exe) or 8(64bit exe)


My guess is that you're overflowing temp[1024] due to the fact that worst case your function can produce double the number of characters given the input.

 

[goth_nerd]

- Since you're adding a space when you encounter that set of chars, temp should be at least double the size of buffer. But you're copying back to buffer, so....buffer should be 2x its allowed content size really.
- strmcpy_s: sizeof(buffer) is going to be 4(32bit exe) or 8(64bit exe)


My guess is that you're overflowing temp[1024] due to the fact that worst case your function can produce double the number of characters given the input.

Well the runtime error only shows when temp = '\n'. So it hasn't encountered the characters as yet. So for example;

Buffer comes in as "#ifndef __STATUSCODES_H__\n" what the method is supposed to do is to remove the new line character; "#ifndef __STATUSCODES_H__". The second time Buffer comes in as "\n" the new line character needs to be removed and an empty string copied back to buffer.

I hope this makes sense

 

[[)roi(]]

Well the runtime error only shows when temp = '\n'. So it hasn't encountered the characters as yet. So for example;

Buffer comes in as "#ifndef __STATUSCODES_H__\n" what the method is supposed to do is to remove the new line character; "#ifndef __STATUSCODES_H__". The second time Buffer comes in as "\n" the new line character needs to be removed and an empty string copied back to buffer.

I hope this makes sense

Where did you get this snippet?

 

[goth_nerd]

Where did you get this snippet?

Are you asking where I got it?

 

[[)roi(]]

Are you asking where I got it?

Yes, Because logically it's not only dealing '\n'
Do you need help with creating one? to replace or remove only '\n'

 

[goth_nerd]

Yes, Because logically it's not only dealing '\n'

It's code I got from work. The guy who wrote it left years ago. I don't understand what you mean when you say it's not only dealing with '\n'

 

[[)roi(]]

It's code I got from work. The guy who wrote it left years ago. I don't understand what you mean when you say it's not only dealing with '\n'

What's the purpose of this part then?.

if (((*pos == '{') ||
			(*pos == '}') ||
			(*pos == ';') ||
			(*pos == ',') ||
			(*pos == '=')) && (lastchar != ' ') || (lastchar == ',') || (lastchar == '='))

/edit Anyway got to run... the snippet you provided is certainly not only intended to focus on substituting newline with spaces.

However if all you really need is to remove or substitute one for the other, then here's some options:

std::string str = "abc\ndef\nghi\n";

//For remove, try this.
str.erase(std::remove(str.begin(), str.end(), '\n'), str.end()); // abcdefghi

// for substitution, try this.
std::string substitute(std::string source, char current, char target) {
  for (int i = 0; i < source.length();i++) {
    if (source[i] == current) {
      source[i] = target;
    }
  }
  return source;
}

std::string str2 = substitute(str, '\n', ' '); // abc def chi

 

[goth_nerd]

What's the purpose of this part then?.

if (((*pos == '{') ||
			(*pos == '}') ||
			(*pos == ';') ||
			(*pos == ',') ||
			(*pos == '=')) && (lastchar != ' ') || (lastchar == ',') || (lastchar == '='))

/edit Anyway got to run... the snippet you provided is certainly not only intended to focus on substituting newline with spaces.

However if all you really need is to remove or substitute one for the other, then here's some options:

std::string str = "abc\ndef\nghi\n";

//For remove, try this.
str.erase(std::remove(str.begin(), str.end(), '\n'), str.end()); // abcdefghi

// for substitution, try this.
std::string substitute(std::string source, char current, char target) {
  for (int i = 0; i < source.length();i++) {
    if (source[i] == current) {
      source[i] = target;
    }
  }
  return source;
}

std::string str2 = substitute(str, '\n', ' '); // abc def chi

Hey just to update you I ended up just creating a string and just used pop_back() to remove the end of line;

strDest = temp;
destLen = strDest.length()  + 1;
strDest.pop_back();

strcpy_s(buffer, destLen, strDest.c_str());

And then the other section just checks if the current character and last character are equal to those characters it just adds a space before the current character. (I think)