Programming Forums > Application Development > C++

Klarre · Aug 8th, 2005, 4:43 PM

I am stucked with a very frustration problem. The program crashes on the getline(...) row. Any ideas why?

#include <iostream>
#include <fstream>

int settingInt(const char* fileName, const char* caption, const char* setting)
{
	std::ifstream file;
	file.open(fileName);
	if(!file.is_open())
		return -2;

	char* tmp;
	while(!file.eof())
	{
		if(file.get() == '[')
		{
			file.getline(tmp, 32, ']'); // CRASH!
			// Continue implement reader here...
		}
	}

	file.close();
	return -1;
}

int main()
{
	std::cout << "Setting: " << settingInt("thefile.ini", "physics", "gravity") << std::endl;

	return 0;
}

The INI file look like this:

(Toggle Plain Text)

[general]
resolutionx=800
resolutiony=600

[physics]
enable=1
gravity=9.82

[keymap]
jump=space
walkforward=w
walkbackward=s
strafeleft=a
straferight=d

Klarre · Aug 8th, 2005, 5:15 PM

Ok, I solved it after a chat with a friend. I changed the char* tmp to a char tmp[32].

prolog · Aug 8th, 2005, 6:30 PM

Hi,

do you know why it crashed ? if not i'll tell you. You did not allocate space for your buffer, so getline tried to write date into memory which did not belong to you. That is where the "big bang" kicked in.

Klarre · Aug 8th, 2005, 6:35 PM

Ah, thanks!

Is there a way to solve it? Use of malloc(), or something like that?

prolog · Aug 8th, 2005, 6:38 PM

Hi,

yes there is a way. As you are coding in c++ new is the operator you'll want to use.

just allocate buffer this way:

(Toggle Plain Text)

char *tmp=new char[32] ;//or whaterver size

//some code

delete [] tmp; //release the buffer

A better way to do things where exception conditions are likly to accure, is to use smart-pointers which exploit RAII to assure that any resources previously acquired are released in all circumstances.

Hope it helped ...

So far ...

Klarre · Aug 8th, 2005, 6:42 PM

Yes, it helped!

Thanks alot!

Animatronic · Aug 8th, 2005, 7:16 PM

Unless this is just for learning, there are win32 functions for reading in an .ini file. Look up GetPrivateProfileString(), and its close related functions.

Klarre · Aug 9th, 2005, 4:21 AM

Yes, it is just for learning. Actually I read about that function, and thought that "I do it myself instead"! I am also coding for BeOS, so I want portable code.

Thanks anyway!

prolog · Aug 9th, 2005, 4:24 AM

Hi Klarre,

if you want something more powerful you could use boost:: program_options for *nixes or boost::serialization for win32 and *nixes.

Infinite Recursion · Aug 9th, 2005, 9:08 AM

I would normally use the 'string' data type in this instance, instead of char*

Aug 8th, 2005, 4:43 PM	#1
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 309 Rep Power: 4	INI-file reader I am stucked with a very frustration problem. The program crashes on the getline(...) row. Any ideas why? (Toggle Plain Text) #include <iostream> #include <fstream> int settingInt(const char* fileName, const char* caption, const char* setting) { std::ifstream file; file.open(fileName); if(!file.is_open()) return -2; char* tmp; while(!file.eof()) { if(file.get() == '[') { file.getline(tmp, 32, ']'); // CRASH! // Continue implement reader here... } } file.close(); return -1; } int main() { std::cout << "Setting: " << settingInt("thefile.ini", "physics", "gravity") << std::endl; return 0; } #include <iostream> #include <fstream> int settingInt(const char* fileName, const char* caption, const char* setting) { std::ifstream file; file.open(fileName); if(!file.is_open()) return -2; char* tmp; while(!file.eof()) { if(file.get() == '[') { file.getline(tmp, 32, ']'); // CRASH! // Continue implement reader here... } } file.close(); return -1; } int main() { std::cout << "Setting: " << settingInt("thefile.ini", "physics", "gravity") << std::endl; return 0; } The INI file look like this: (Toggle Plain Text) [general] resolutionx=800 resolutiony=600 [physics] enable=1 gravity=9.82 [keymap] jump=space walkforward=w walkbackward=s strafeleft=a straferight=d [general] resolutionx=800 resolutiony=600 [physics] enable=1 gravity=9.82 [keymap] jump=space walkforward=w walkbackward=s strafeleft=a straferight=d

Aug 8th, 2005, 6:30 PM	#3
prolog Programmer Join Date: Jul 2005 Location: Germany Posts: 69 Rep Power: 4	Hi, do you know why it crashed ? if not i'll tell you. You did not allocate space for your buffer, so getline tried to write date into memory which did not belong to you. That is where the "big bang" kicked in. __________________ -= C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do succeed, you will blow away your whole leg. =- Bjarne Stroustrup

Aug 8th, 2005, 6:38 PM	#5
prolog Programmer Join Date: Jul 2005 Location: Germany Posts: 69 Rep Power: 4	Hi, yes there is a way. As you are coding in c++ new is the operator you'll want to use. just allocate buffer this way: (Toggle Plain Text) char tmp=new char[32] ;//or whaterver size //some code delete [] tmp; //release the buffer char tmp=new char[32] ;//or whaterver size //some code delete [] tmp; //release the buffer A better way to do things where exception conditions are likly to accure, is to use smart-pointers which exploit RAII to assure that any resources previously acquired are released in all circumstances. Hope it helped ... So far ... __________________ -= C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do succeed, you will blow away your whole leg. =- Bjarne Stroustrup

Aug 9th, 2005, 4:24 AM	#9
prolog Programmer Join Date: Jul 2005 Location: Germany Posts: 69 Rep Power: 4	Hi Klarre, if you want something more powerful you could use boost:: program_options for nixes or boost::serialization for win32 and nixes. __________________ -= C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do succeed, you will blow away your whole leg. =- Bjarne Stroustrup

Aug 9th, 2005, 9:08 AM	#10
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	I would normally use the 'string' data type in this instance, instead of char* __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Aug 8th, 2005, 5:15 PM	#2
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 309 Rep Power: 4	Ok, I solved it after a chat with a friend. I changed the char* tmp to a char tmp[32].

Aug 8th, 2005, 6:35 PM	#4
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 309 Rep Power: 4	Ah, thanks! Is there a way to solve it? Use of malloc(), or something like that?

Aug 8th, 2005, 6:42 PM	#6
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 309 Rep Power: 4	Yes, it helped! Thanks alot!

Aug 8th, 2005, 7:16 PM	#7
Animatronic Programmer Join Date: Jun 2005 Posts: 99 Rep Power: 4	Unless this is just for learning, there are win32 functions for reading in an .ini file. Look up GetPrivateProfileString(), and its close related functions.

Aug 9th, 2005, 4:21 AM	#8
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 309 Rep Power: 4	Yes, it is just for learning. Actually I read about that function, and thought that "I do it myself instead"! I am also coding for BeOS, so I want portable code. Thanks anyway!

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Programming Forums > Application Development > C++

INI-file reader