bug#46797: mac_font_shape EXC_BAD_ACCESS

[Alan Third]

On Fri, Feb 26, 2021 at 04:30:13PM +0000, Jimmy Yuen Ho Wong wrote:
> Emacs crash on the NSPort of emacs27 HEAD, here's the LLDB info:
> 
> Process 94921 stopped
> * thread #1, queue = 'com.apple.main-thread', stop reason =
> EXC_BAD_ACCESS (code=1, address=0x7ffeefc00000)
>     frame #0: 0x00000001003abd3a
> Emacs`mac_font_shape(font=0x000000011fb480c0, string=@"𝆺𝅥𝅯𝉂\0\0\0\0",
> glyph_layouts=0x00007ffeefbe9a50, glyph_len=8, dir=DIR_UNKNOWN) at
> macfont.m:3754:34
>    3751               struct mac_glyph_layout *gl =
>    3752                 glbuf + range.location + range.length;
>    3753
> -> 3754               if (gl->comp_range.length
>    3755                   > comp_range.location + comp_range.length)
>    3756                 comp_range.length = gl->comp_range.length -
> comp_range.location;
>    3757               min_location = gl->comp_range.location;
> Target 0: (Emacs) stopped.
> (lldb) bt --all
> error: bt [<digit> | all]
> (lldb) bt all
> * thread #1, queue = 'com.apple.main-thread', stop reason =
> EXC_BAD_ACCESS (code=1, address=0x7ffeefc00000)
>   * frame #0: 0x00000001003abd3a
> Emacs`mac_font_shape(font=0x000000011fb480c0, string=@"𝆺𝅥𝅯𝉂\0\0\0\0",
> glyph_layouts=0x00007ffeefbe9a50, glyph_len=8, dir=DIR_UNKNOWN) at
> macfont.m:3754:34
>     frame #1: 0x00000001003a529e
> Emacs`macfont_shape(lgstring=0x0000000106e2f005,
> direction=0x0000000000000000) at macfont.m:3000:16

The interesting bit here is missing.

Can you repeat the crash and give us a recipe?
-- 
Alan Third