Hello,
I'm currently updating the Android FreeType sources to the latest CVS. In
doing so, I noticed something that unfortunately
escaped me before that: we added a new field to a publicly declared
structure, thus breaking the ABI.
More specifically, the declaration of PS_FontInfoRec in
include/freetype/t1tables.h is now:
typedef struct PS_FontInfoRec_
{
FT_String* version;
FT_String* notice;
FT_String* full_name;
FT_String* family_name;
FT_String* weight;
FT_Long italic_angle;
FT_Bool is_fixed_pitch;
FT_Short underline_position;
FT_UShort underline_thickness;
* /* since 2.3.8 */
FT_UShort fs_type;
*
} PS_FontInfoRec;
the problem is that this structure can be allocated by the user (either in
the heap or the stack), e.g. when calling
a function like FT_Get_PS_Font_Info declared as:
FT_EXPORT( FT_Error )
FT_Get_PS_Font_Info( FT_Face face,
PS_FontInfo afont_info );
*This is very bad* !!.
It means that any client code that was built against 2.3.7 or older will now
experience a nice
silent stack or heap memory corruption whenever it calls this function in
2.3.8.
I suggest that we do the following instead:
- remove the field from the definition
- provide a new function to retrieve the corresponding information, as in
FT_Get_PS_FsType() or whatever, that will not break the ABI
- release 2.3.9 ASAP explaining why.
I really hope that there isn't any code that relies on this new field out
there.
Generalyl speaking, we should *NOT* add fields to public structures, except
a very few instances where we know that the
corresponding object should never be stack or heap allocated by the user
(FT_Face or FT_GlyphSlot for example). Even
in these cases, I'd really prefer that we discuss such changes on the
development mailing list before hand.
- David
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