Crash with no error message: spaces(-1)

Author

Message

Nieb

10

Years of Service

User Offline

Joined: 13th May 2014

Location: Lurking

Posted: 22nd Jun 2022 23:56

Link

If spaces(-1) is executed the app will crash. It just disappears, no error message box.

Back to top

Profile PM

Virtual Nomad

Moderator

18

Years of Service

User Offline

Joined: 14th Dec 2005

Location: SF Bay Area, USA

Posted: 23rd Jun 2022 01:29

Link

This post has been marked by the post author as the answer.

confirmed. issue added to the repo: https://github.com/TheGameCreators/AGK-Studio/issues/996

AGK Resource Directory
Made with AppGameKit on Itch.io
TGC @ GitHub
Some Snippets

Back to top

Profile PM Website

Dark Raven

10

Years of Service

User Offline

Joined: 27th Jul 2014

Location: United States

Posted: 25th Jun 2022 04:48

Link

I'm not sure about the crashing with error message but I believe it probably has something to do with the negative 1. On the help site if you set to show c++ version it is looking to pass a unsigned integer which mean there should be an error message because of the passing of a negative number. So the lack of error and crashing is a bug but the negative number is probably what is causing it. So I'm wondering if any other function that can't take a negative number will do the same thing.

Back to top

Profile PM Website

Nieb

10

Years of Service

User Offline

Joined: 13th May 2014

Location: Lurking

Posted: 4th Jul 2022 15:13

Link

After the update it now shows the new error message with spaces(0). This was fine before, it did not cause a crash.

Back to top

Profile PM

Virtual Nomad

Moderator

18

Years of Service

User Offline

Joined: 14th Dec 2005

Location: SF Bay Area, USA

Posted: 4th Jul 2022 16:04 Edited at: 4th Jul 2022 16:05

Link

yah, i'd say the bug is a little worse now.

i dont want an error on 0. we might have a variable that inserts spaces for formatting reasons and 0 should be valid.

seems like the attempted fix did:

+ Code Snippet

If Spaces() = 0 then Error()

vs

+ Code Snippet

If Spaces() < 0

ie, probably a simple typo which is why i want to see the fix in the first place.

ah, well. in the meantime:

+ Code Snippet

do
	For x = -1 to 1
		print(Space(x) + "Hello!")
	next x
	
	Print(ScreenFPS())
	Sync()
loop

Function Space(x)
	if x > 0 then Result$ = Spaces(x) else Result$ = ""
EndFunction Result$

AGK Resource Directory
Made with AppGameKit on Itch.io
TGC @ GitHub
Some Snippets

Back to top

Profile PM Website

Zaxxan

Developer

4

Years of Service

User Offline

Joined: 17th Nov 2020

Location: England

Posted: 6th Jul 2022 15:16

Link

Unfortunately this is unlikely to get fixed for another 3 months.

Back to top

Profile PM

MadBit

VIP Member

Gold Codemaster

15

Years of Service

User Offline

Joined: 25th Jun 2009

Location: Germany

Posted: 7th Jul 2022 12:19

Link

From the github repository -

+ Code Snippet

//****f* Core/Strings/Spaces
// FUNCTION
//   Creates a string of spaces equal to the length passed in.
// INPUTS
//   length -- The length of the string of spaces to create
// SOURCE
char* agk::Spaces( UINT length )
//****
{
	if ( length <= 0 )
	{
#ifdef _AGK_ERROR_CHECK
		agk::Error ( "Negative valued passed into the Spaces command" );
#endif
		return 0;
	}

	char *str = new char[ length+1 ];
	UINT n = 0;
	for ( n=0; n<length; n++ ) str[n]=32;
	str[n]=0;
	return str;
}

The way the function is set up here, it should never stop at negative values.
Since the parameter length is defined as unsigned int (as Dark Raven has already noted), a -1 in hex notation would be equal to 0xffffffff (32 bit) and always positive.
Consequently, the termination condition is never reached.
Or do I see this wrong?

Share your knowledge. It\'s a way to achieve immortality. (Tenzin Gyatso)

Back to top

Profile PM Email

Nieb

10

Years of Service

User Offline

Joined: 13th May 2014

Location: Lurking

Posted: 7th Jul 2022 16:29 Edited at: 7th Jul 2022 16:35

Link

Good catch. I've noticed if you, mistakenly, put a print() in a long loop bad things happen, even if the loop only executes once.

Example:

+ Code Snippet

FOR i = 0 TO 100000
    Print("ABC 123 !?")
NEXT i
Sync()

DO
    Print(ScreenFPS())
    Sync()
LOOP

Here, my FPS will only be ~17 after running the long print loop only once. Also, windows reports using 600MB of RAM and high CPU usage.

So, perhaps the original issue wasn't "can't do negative spaces" but, instead "can't print a string with 4294967295 characters".
Maybe the print() function could use some safety checks on string-length and number-of-calls per-frame.

Only changing the spaces() code to: if ( length < 0 ) is still fine. If the most significant bit (or signed bit) is set it's a good indication something went wrong.

Back to top

Profile PM

MadBit

VIP Member

Gold Codemaster

15

Years of Service

User Offline

Joined: 25th Jun 2009

Location: Germany

Posted: 8th Jul 2022 06:45

Link

Nieb wrote: "So, perhaps the original issue wasn't "can't do negative spaces" but, instead "can't print a string with 4294967295 characters".
Maybe the print() function could use some safety checks on string-length and number-of-calls per-frame."

This is how it will have been.
Since +1 is added to the length when reserving memory, there is an integer overflow and possibly 0xffffff becomes 0x00000000 again.
Thus, 0 bytes would be reserved for the string.
If one then writes into it, there is of course a memory error.

The correct if statement would rather be the following.

+ Code Snippet

    if ( length > 0x7fffffff )
    {
#ifdef _AGK_ERROR_CHECK
        agk::Error ( "Negative valued passed into the Spaces command" );
#endif
        return 0;
    }

But I also wonder if a string of more than 2 terrabytes should be allowed.
That is just my opinion.

Share your knowledge. It\'s a way to achieve immortality. (Tenzin Gyatso)

Back to top

Profile PM Email

Sorry your browser is not supported!

AppGameKit Classic Chat / [SOLVED] Crash with no error message: spaces(-1)