Re: [ft-devel] More crashes on ARM

[david turner]

Sorry, I should have been more accurate.

You should set the watchpoint just after the creation of the FT_CMap
object (this happens in FT_CMap_New in src/base/ftobjs.c). there is
code like this:

   if ( !FT_ALLOC( cmap, clazz->size ) )
   {
     cmap->charmap = *charmap;
     cmap->clazz   = clazz;

     if ( clazz->init )
     {
       error = clazz->init( cmap, init_data );
       if ( error )
         goto Fail;
     }

     /* add it to our list of charmaps */

you should set the watchpoint after the "cmap->clazz = clazz" statement.
So it should be:

- first set a breakpoint at the "cmap->clazz = clazz" statement
 (line 2598 of current CVS)

- when the breakpoint is reached, add a watchpoint to the
 memory location of the 'clazz' field, i.e.:

    p &cmap->clazz
    0x6734efd4                          (or some other value)
    watch *(char*)0x6734efd4   (replace with previous value)
    c

- repeat each time the first breakpoint is reached (there may be
 several charmaps in the font)

the watchpoint should trigger whenever the memory location is
updated. Note that the watchpoint should make things run very
slowly on some platforms.

Hope this helps,

- David

  


Frank Meerkoetter a écrit :
> Quoting david turner <address@hidden>:
>
> Hi,
>
> > Can you put a watchpoint on the cmap's "clazz" field to detect where it
> > is over-written ?
> > Really, it should give us meaningful information.
>
> I'm not sure if i understand correctly what you wan't me to do.
> The crash happens directly after cmap becomes available.
>
> FT_EXPORT_DEF( FT_ULong )
>   FT_Get_Next_Char( FT_Face   face,
>                     FT_ULong  charcode,
>                     FT_UInt  *agindex )
>   {
>  [...]
>       FT_UInt32  code = (FT_UInt32)charcode;
>       FT_CMap    cmap = FT_CMAP( face->charmap );           // <---
>
>
>       gindex = cmap->clazz->char_next( cmap, &code );       // <--- crash
>       result = ( gindex == 0 ) ? 0 : code;
>     }
>  [...]
>   }
>
> I tried it anyways but had no success.
>
> Breakpoint 2, FT_Get_Next_Char (face=0x4bb90, charcode=0, 
> agindex=0xbefff748)
>     at ftobjs.c:2426
> 2426        FT_ULong  result = 0;
> Current language:  auto; currently c
> (gdb) n
> 2427        FT_UInt   gindex = 0;
> (gdb) n
> 2430        if ( face && face->charmap )
> (gdb) n
> 2432          FT_UInt32  code = (FT_UInt32)charcode;
> (gdb) n
> 2433          FT_CMap    cmap = FT_CMAP( face->charmap );
> (gdb) n
> 2436          gindex = cmap->clazz->char_next( cmap, &code );
> (gdb) watch cmap->clazz
> Watchpoint 3: cmap->clazz
> (gdb) c
> Continuing.
> 0x00000000 in ?? ()
> Cannot access memory at address 0x0
>
>
> Regards,
>    Frank

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