bug#21556: 25.0.50; Memory leak in emacs -Q with lucid (font)

[Dima Kogan]

Dmitry Antipov <dmantipov@yandex.ru> writes:

> On 10/01/2015 09:50 PM, Dima Kogan wrote:
>
>> OK, so are you suggesting changing how mark_face_cache() works? How bad
>> is it to accept that fonts and font entities are not necessarily linked,
>> and to install the latest patch in this bug?
>
> I'm suggesting to check whether there are unmarked font objects after marking
> from Vfontset_table, and, if so, understand whether it's correct. Otherwise
> your patch, even being correct by itself, may just hide subtle GC bug.

Hi. I looked at this again. Running the same test as before (emacs -Q,
repeatedly creating/destroying client frame) I see:


- entities are created with each new client frame but are /never/
  marked.

- entity-creation backtrace is always

  #0  0x000000000060e74e in font_make_entity () at font.c:173
  #1  0x00000000006793ae in ftfont_pattern_entity (p=0xf8c180, extra=20784563) 
at ftfont.c:215
  #2  0x000000000067b952 in ftfont_list (f=0x13fb8c0, spec=13463989) at 
ftfont.c:1057
  #3  0x0000000000680de6 in xftfont_list (f=0x13fb8c0, spec=13463989) at 
xftfont.c:138
  #4  0x0000000000615ebc in font_list_entities (f=0x13fb8c0, spec=20978277) at 
font.c:2780
  #5  0x0000000000617c27 in font_find_for_lface (f=0x13fb8c0, 
attrs=0x7fff3ee81f50, spec=20082933, c=-1) at font.c:3262
  #6  0x0000000000617fb0 in font_load_for_lface (f=0x13fb8c0, 
attrs=0x7fff3ee81f50, spec=20082933) at font.c:3335
  #7  0x00000000006183a2 in font_open_by_spec (f=0x13fb8c0, spec=20082933) at 
font.c:3429
  #8  0x0000000000618415 in font_open_by_name (f=0x13fb8c0, name=13702436) at 
font.c:3440
  #9  0x000000000052fec4 in x_default_font_parameter (f=0x13fb8c0, 
parms=20784979) at xfns.c:2904
  #10 0x0000000000530bc2 in Fx_create_frame (parms=20784979) at xfns.c:3139

- Vfontset_table has fontsets and font-specs in it, but NO
  font-entities. Marking from the Vfontset_table thus cannot mark any
  font entities.

Where are the entities supposed to be referenced? Does it make sense
they're never marked?