Crash on ofstream declaration...

**yaya** · 07-17-2010

I'm making a sort of I/O wrapper for a larger project, but all of a sudden this crash has appeared. I have narrowed it down to this line:

Code:

std::ofstream test;

Not very elaborate, eh?

The thing is, this line was called a few times before, and worked fine. But after a certain amount of times, if crashes with this message:

"Unhandled exception at 0x76b8b727 in fileconvert.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x0035f2c0.."

And it directs me to line 376 in 'mlock.c'. I have done extensive debugging and can't find the problem. Can anyone point me in the right direction?

Cheers.

**laserlight** · 07-17-2010

Perhaps the problem lies elsewhere (e.g., undefined behaviour due to buffer overflow), but merely is manifested at this line.

**CodeMonkey** · 07-17-2010

Is test declared at the beginning of a new scope? Maybe one of your trailing destructors made a mess.

**yaya** · 07-17-2010

The code I gave you before was test code (obviously) but here is the actuall code:

Code:

FILEIOASCII::FILEIOASCII( std::string& Filename, __int8 OpenType, bool Append ) : OpenType( OpenType )
{
	iFile = NULL;
	oFile = NULL;

	if ( OpenType == IO_READ )
		iFile = new std::ifstream( Filename.c_str() ); // crash here

	else if ( OpenType == IO_WRITE )
	{
		oFile = new std::ofstream( Filename.c_str(), ( Append ? std::ios::app : std::ios::trunc ) ); // crash here
	}

	else
		WNG( "File has incorrect open type." );
};

I also noticed that it crashes when doing an ifstream as well (I pointed it out in the above code.

What I have done is I have called this code once (I create an object with this constructor). Then when I call it again, I get an error.
Also, if I call this constructor once, then I try to create and o/ifsteam, it still crashes. So this code (or somewhere else) is affecting fstream somehow.

**laserlight** · 07-18-2010

Originally Posted by yaya

What I have done is I have called this code once (I create an object with this constructor). Then when I call it again, I get an error.

Show this part of your code. Also, did you disable the the copy constructor and copy assignment operator of FILEIOASCII? Did you implement the destructor correctly? Why are you storing pointers to std::ifstream and std::ofstream in the first place?

**yaya** · 07-18-2010

Originally Posted by laserlight

Show this part of your code.

There isn't really much to show... but:

Code:

// first time
FILEIOASCII File( Filename, IO_READ );

// second time
FILEIOASCII File( Filename, IO_WRITE );

Also, did you disable the the copy constructor and copy assignment operator of FILEIOASCII? Did you implement the destructor correctly? Why are you storing pointers to std::ifstream and std:

fstream in the first place?

I tried changing the pointers to non-pointers and the problem still happened. There are no other pointers in the class so I don't think a copy constructor/copy assignment operator would be the cause.

Just to clear things up, here's the rest of the code for that class:

Code:

class FILEIOASCII
{
public:
	FILEIOASCII( std::string& Filename, __int8 OpenType, bool Append = false );
	~FILEIOASCII();

	template < typename T > bool Action( T& Data );
	bool IsEOF();

private:
	std::ifstream iFile;
	std::ofstream oFile;

	__int8 OpenType;
};

template < typename T > bool FILEIOASCII::Action( T& Data )
{
	if ( OpenType == IO_READ )
	{
		iFile >> Data;
		return true;
	}

	else if ( OpenType == IO_WRITE )
	{
		oFile << Data;
		oFile << ' ';
		return true;
	}

	WNG( "File has incorrect open type." );
	return false;
};

FILEIOASCII::~FILEIOASCII()
{
	if ( OpenType == IO_READ )
		iFile.close();
	else if ( OpenType == IO_WRITE )
		oFile.close();
	else
		WNG( "File has incorrect open type." );
};

bool FILEIOASCII::IsEOF()
{
	return OpenType == IO_READ ? iFile.eof() : oFile.eof();
};

**laserlight** · 07-18-2010

Originally Posted by yaya

There isn't really much to show... but:

How did you manage to use the name File for two different variables in the same scope?

Anyway, I tested with this:

Code:

#include <string>
#include <fstream>
#include <cassert>

class FileIoAscii
{
public:
    enum IoType {io_read, io_write};

    FileIoAscii(const std::string& name, IoType io_type_)
        : io_type(io_type_)
    {
        if (io_type == io_read)
        {
            in.open(name.c_str());
        }
        else if (io_type == io_write)
        {
            out.open(name.c_str());
        }
        else
        {
            assert(!"Invalid I/O type.");
        }
    }
private:
    std::ifstream in;
    std::ofstream out;

    IoType io_type;

    FileIoAscii(const FileIoAscii&);
    void operator=(const FileIoAscii&);
};

int main()
{
    const std::string filename("test.c");
    FileIoAscii one(filename, FileIoAscii::io_read);
    FileIoAscii two(filename, FileIoAscii::io_write);
}

Frankly, it works as expected, i.e., the program did not crash. Therefore, from what you showed, the problem most likely lies elsewhere, in the code that you did not show.

**yaya** · 07-18-2010

Oh, they weren't in the same scope. I was just simplifying code. I guess I'll just keep searching. Thanks for the help.

**laserlight** · 07-18-2010

Originally Posted by yaya

Oh, they weren't in the same scope. I was just simplifying code.

It is good to simplify, but the simplification must still demonstrate the problem, otherwise it will not reveal anything (other than a better way of doing things, if you're lucky).

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