Re: NSMenu menu position saving bug (PATCH)

[Richard Frith-Macdonald]

On 10 Jan 2004, at 16:23, Michael Hanni wrote:

> Hi,
>
> On 2004-01-10 01:59:05 -0700 Richard Frith-Macdonald 
> <richard@brainstorm.co.uk> wrote:
>
> > On 10 Jan 2004, at 15:13, Michael Hanni wrote:
> > > so the key was always nil (interestingly enough, if I manually 
> > > edited the key in the defaults to be \033Info it worked properly). I 
> > > changed this to:
> > So it sounds like the escape character was not saved into the 
> > defaults ... either a problem with the escape in the string, or a 
> > problem with converting it back to the four character sequence ('\\', 
> > '0', '3', '3') it should be coded as in the defaults database.
>
> If I change this to \\033 instead of \033 it works ok... Is it that 
> when you give \033Info to NSString in a cstring it tries to come up 
> with a character with value 033I?

When given a string literal '@"\033%@"' in the source code, the 
Objective-C compiler (gcc) produces an NSConstantString object pointing 
to a four byte sequence - escape, percent, at, nul

At runtime, the GSFormat() function should initialise an NSString from 
this to contain 5 unicode characters - escape, I, n, f, o

When storing the key into the defaults database, the PString() function 
should convert this to 8 ascii characters - backslash, 0, 3, 3, I, n, 
f, o

> With the current code, minus my modification, my defaults are always 
> this:
>
>         NSMenuLocations = {
>             "\000" = "136 379 77 233 0 0  960 768 ";
>             "\000Edit" = "626 325 79 128 0 0  960 768 ";
>         };
>
> Notice the key is "\000" not "\033". So on the console I see "dit".

So something is going very wrong!   If you could step through the code 
under gdb and examine what's going on, you could perhaps track this 
down.

> > More importantly, if something is going wrong with strings containing 
> > escape characters, you may have much more fundamental problems than 
> > just losing your menu location!
>
> I'm guessing \033I is not a valid escape character?

\033 means the octal value 033, which is the decimal value 27, which is 
the ascii 'escape' control character.

> > Two places to look ... The string is initialised by code in 
> > base/Source/GSFormat.m
> > The output conversion for the defaults database is in 
> > GSCompatibility.m (the PString() function)
>
> I looked at this code, but it is way over my head.

It's hard to figure things out just by looking at the source ... I 
think stepping through the relevant parts in gdb and examining the data 
as it is modified  is probably the way to go ... that's likely to help 
figure out why your system is behaving differently from other peoples.

> Anyhow, using "+" or even "\\033" the defaults are saved correctly. 
> With only "\033" it fails everytime on my machine.
>
> This is on a powerpc machine, debian linux, gcc 3.3.3-0pre1, and libc6 
> 2.3.2.ds1-10.
>
> Any ideas?

Just one ... I think powerpc systems use a different byte order from 
intel systems ...
maybe there is some problem with accessing the wrong byte of the 16-bit 
unicode characters.
I'll look and see if I can spot anything in the source.