plib-users

[Plib-users] PUI: getLegend bug?

[SkyFlash <sky...@ch...>]

I just discovered that setLegend will copy my char* instead of copying
the content, so if I pass in
a constant like "Value" it crashes after the memory is out of scope.
Also if I pass in a temporary variable and delete
it afterwards it crashes....

How am I supposed to change the value of the legend of a widget after
its created?

Ralf Pietersz

Re: [Plib-users] PUI: getLegend bug?

[Eero P. <epa...@ko...>]

SkyFlash wrote:
> I just discovered that setLegend will copy my char* instead of copying
> the content, so if I pass in
> a constant like "Value" it crashes after the memory is out of scope.

This is odd, I don't think C-language string constants (literals)
should be destroyed or become invalid when they are "out of scope"-

Certainly the most typical legend usage I have is:

button->setLegend("My Button");

and it works fine. C++ standard library "strings" are an other thing,
and they might cause problems.

> Also if I pass in a temporary variable and delete
> it afterwards it crashes....
> 

Yes, this is to be expected.

> How am I supposed to change the value of the legend of a widget after
> its created?
> 

If I have needed to "inplace edit" widget legends I have either used
static char arrays or dynamically allocated memory buffers, which
I have then passed to setLegend. Of course for dynamic allocation the
buffer cannot be freed before the widget has been destroyed.



		Eero

RE: [Plib-users] PUI: getLegend bug?

[SkyFlash <sky...@ch...>]

> This is odd, I don't think C-language string constants
> (literals) should be destroyed or become invalid when they 
> are "out of scope"-

Neither did I. :)

> Certainly the most typical legend usage I have is:
> 
> button->setLegend("My Button");
> 
> and it works fine. C++ standard library "strings" are an
> other thing, and they might cause problems.

Well, what I did was something like this:

string charactername;

if (characterexists)
	m_characterselect->setLegend (charactername.c_str())
else
	m_characterselect->setLegend ("None")

Now, wheneever there was no character and the static "None" was set it
crashed.
This here works fine:

if (characterexists)
	m_characterselect->setLegend (charactername.c_str())
//else
//	m_characterselect->setLegend ("None")

And it displays the character names on the buttons. Of course it
probably trashes memory at some point. :P

Ralf Pietersz

Re: [Plib-users] PUI: getLegend bug?

[Eero P. <epa...@ko...>]

SkyFlash wrote:

> 
> Well, what I did was something like this:
> 
> string charactername;
> 
> if (characterexists)
> 	m_characterselect->setLegend (charactername.c_str())
> else
> 	m_characterselect->setLegend ("None")
> 

I get a creepy feeling when I see the c_str()...
The value returned from it certainly doesn't stay valid
if you in anyway change the charactername string, including
allowing it to go out of scope.

On the other hand even if I understand how this would cause
corrupted output, it is not so obvious what would cause the
actual crash. That might depend on the malloc implementation
though.



		Eero