Re: Building the igc branch on MS-Windows

[Helmut Eller]

> installed this in your name, with one difference:
>
>> +    if (FRAME_WINDOW_P (f) && FRAME_OUTPUT_DATA (f))
>> +      {
>> +    struct font *font = FRAME_FONT (f);
>> +    if (font)
>> +      IGC_FIX12_RAW(ss, &FRAME_FONT (f));
>
> You already used FRAME_FONT, so not necessary to use it again:
>
>     if (FRAME_WINDOW_P (f) && FRAME_OUTPUT_DATA (f))
>       {
>       struct font *font = FRAME_FONT (f);
>       if (font)
>         IGC_FIX12_RAW(ss, &font);  <<<<<<<<<<<<<<<<<<<<<
>       }

I think this change introduced a bug.  Remember that MPS is moving
GC. So it sometimes needs to update the pointer in the struct that we
are scanning.  We have to give it the address of the field, not the
address of some local variable on the stack. Perhaps clearer is this:

        struct font **font = &FRAME_FONT (f);
        if (*font)
          IGC_FIX12_RAW(ss, font);

> However, the crashes while scrolling through xdisp.c are still there.
> I just had 2 of them; backtraces below.  It sounds like the first one
> is due to Lisp strings, but the second one is related to markers.
>
>   igc.c:1584: Emacs fatal error: assertion failed: !"other"

Yes, I see this too.  I will try to write some code to reproduce
this without needing manual input.

Helmut