new compiler warnings since 2.10.x

[Hin-Tak Leung]

Hi Werner and the rest of the gang,

Am trying to ugrade my system to fedora 36 (with my FontVal-customized 
backend...) and saw quite a large number of new compiler warnings... so I 
checked my past build logs, and see that a few of them were new to 2.11.1 
(2.11.0 was clean), and a few more added in 2.12.x . Details below.

Hin-Tak

P.S. had a quick look, seem some of these are old codes and used to be compiled 
out, but somehow FT_CONFIG_OPTION_INCREMENTAL is now on. The color and rsvg 
stuff look new. Not sure about the memset().


freetype-2.12.1/src/truetype/ttgload.c: In function 'load_truetype_glyph':
freetype-2.12.1/src/truetype/ttgload.c:1697:22: warning: storing the address of 
local variable 'inc_stream' in 'loader_482(D)->stream' [-Wdangling-pointer=]
 1697 |       loader->stream = &inc_stream;
      |       ~~~~~~~~~~~~~~~^~~~~~~~~~~~~
freetype-2.12.1/src/truetype/ttgload.c:1627:21: note: 'inc_stream' declared here
 1627 |     FT_StreamRec    inc_stream;
      |                     ^~~~~~~~~~
freetype-2.12.1/src/truetype/ttgload.c:1627:21: note: 'loader_482(D)' declared 
here


freetype-2.12.1/src/smooth/ftgrays.c: In function 'gray_convert_glyph':
freetype-2.12.1/src/smooth/ftgrays.c:1968:20: warning: storing the address of 
local variable 'buffer' in 'worker_56(D)->ycells' [-Wdangling-pointer=]
 1968 |     ras.ycells     = (PCell*)buffer;
      |                    ^
freetype-2.12.1/src/smooth/ftgrays.c:1950:14: note: 'buffer' declared here
 1950 |     TCell    buffer[FT_MAX_GRAY_POOL];
      |              ^~~~~~
freetype-2.12.1/src/smooth/ftgrays.c:1950:14: note: 'worker_56(D)' declared here


freetype-2.12.1/src/smooth/ftgrays.c:1961:26: warning: storing the address of 
local variable 'buffer' in 'worker_41(D)->cell_null' [-Wdangling-pointer=]
 1961 |     ras.cell_null        = buffer + FT_MAX_GRAY_POOL - 1;
      |                          ^
freetype-2.12.1/src/smooth/ftgrays.c:1950:14: note: 'buffer' declared here
 1950 |     TCell    buffer[FT_MAX_GRAY_POOL];
      |              ^~~~~~
freetype-2.12.1/src/smooth/ftgrays.c:1950:14: note: 'worker_41(D)' declared here


In function 'memset',
    inlined from 'af_face_globals_new' at 
freetype-2.12.1/src/autofit/afglobal.c:345:5:
/usr/include/bits/string_fortified.h:59:10: warning: '__builtin_memset' writing 
696 bytes into a region of size 0 overflows the destination 
[-Wstringop-overflow=]
   59 |   return __builtin___memset_chk (__dest, __ch, __len,
      |          ^


src/rsvg-port.c: In function 'rsvg_port_preset_slot':
src/rsvg-port.c:309:7: warning: 'rsvg_handle_render_cairo' is deprecated: Use 
'rsvg_handle_render_document' instead [-Wdeprecated-declarations]
  309 |       ret = rsvg_handle_render_cairo ( handle, rec_cr );
      |       ^~~
In file included from /usr/include/librsvg-2.0/librsvg/rsvg.h:1450,
                 from src/rsvg-port.c:25:
/usr/include/librsvg-2.0/librsvg/rsvg-cairo.h:88:10: note: declared here
   88 | gboolean rsvg_handle_render_cairo (RsvgHandle *handle, cairo_t *cr);
      |          ^~~~~~~~~~~~~~~~~~~~~~~~
src/rsvg-port.c:323:7: warning: 'rsvg_handle_render_cairo_sub' is deprecated: 
Use 'rsvg_handle_render_layer' instead [-Wdeprecated-declarations]
  323 |       ret = rsvg_handle_render_cairo_sub( handle, rec_cr, str );
      |       ^~~
/usr/include/librsvg-2.0/librsvg/rsvg-cairo.h:153:10: note: declared here
  153 | gboolean rsvg_handle_render_cairo_sub (RsvgHandle *handle, cairo_t *cr, 
const char *id);
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~


ft2demos-2.12.1/graph/gblblit.c: In function '_gblender_spans_rgb565':
ft2demos-2.12.1/graph/gblblit.c:158:69: warning: 'color' is used uninitialized 
[-Wuninitialized]
  158 | #define  GDST_PIX(p,d)           unsigned int  p = 
GRGB565_TO_RGB24(*(unsigned short*)(d))
      |                                                                     ^
In file included from ft2demos-2.12.1/graph/gblblit.c:178:
ft2demos-2.12.1/graph/gblany.h:49:19: note: 'color' declared here
   49 |   grColor         color   = surface->color;
      |                   ^~~~~
ft2demos-2.12.1/graph/gblblit.c: In function '_gblender_spans_rgb555':
ft2demos-2.12.1/graph/gblblit.c:187:69: warning: 'color' is used uninitialized 
[-Wuninitialized]
  187 | #define  GDST_PIX(p,d)           unsigned int  p = 
GRGB555_TO_RGB24(*(unsigned short*)(d))
      |                                                                     ^
In file included from ft2demos-2.12.1/graph/gblblit.c:207:
ft2demos-2.12.1/graph/gblany.h:49:19: note: 'color' declared here
   49 |   grColor         color   = surface->color;
      |                   ^~~~~