Found while fuzzing m-c 20210609-662aa4502f55 (--enable-address-sanitizer --enable-fuzzing)

To help catch this issue ASAN_OPTIONS=detect_leaks=1 was used.

Direct leak of 768 byte(s) in 1 object(s) allocated from:
    #0 0x55dc23641289 in realloc /builds/worker/fetches/llvm-project/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
    #1 0x48594f52ce6a in _cairo_array_grow_by /gecko/gfx/cairo/cairo/src/cairo-array.c:115:20
    #2 0x48594f52d621 in _cairo_array_allocate /gecko/gfx/cairo/cairo/src/cairo-array.c:317:14
    #3 0x48594f52d4b2 in _cairo_array_append_multiple /gecko/gfx/cairo/cairo/src/cairo-array.c:288:14
    #4 0x48594f52d3c1 in _cairo_array_append /gecko/gfx/cairo/cairo/src/cairo-array.c:265:12
    #5 0x48594f364a69 in cff_index_read /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:438:22
    #6 0x48594f36f2fd in cairo_cff_font_read_cid_fontdict /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:1020:14
    #7 0x48594f36c404 in cairo_cff_font_read_top_dict /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:1230:18
    #8 0x48594f36a4e3 in cairo_cff_font_read_font /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:1349:18
    #9 0x48594f36246f in cairo_cff_font_generate /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:2581:14
    #10 0x48594f36045d in _cairo_cff_subset_init /gecko/gfx/cairo/cairo/src/cairo-cff-subset.c:2973:14
    #11 0x48594f427c99 in _cairo_pdf_surface_emit_cff_font_subset /gecko/gfx/cairo/cairo/src/cairo-pdf-surface.c:5903:14
    #12 0x48594f4272c4 in _cairo_pdf_surface_emit_unscaled_font_subset /gecko/gfx/cairo/cairo/src/cairo-pdf-surface.c:6618:14
    #13 0x48594f669ca2 in _cairo_sub_font_collect /gecko/gfx/cairo/cairo/src/cairo-scaled-font-subsets.c:741:30
    #14 0x48594f636736 in _cairo_scaled_font_subsets_foreach_internal /gecko/gfx/cairo/cairo/src/cairo-scaled-font-subsets.c:1062:6
    #15 0x48594f636986 in _cairo_scaled_font_subsets_foreach_unscaled /gecko/gfx/cairo/cairo/src/cairo-scaled-font-subsets.c:1090:12
    #16 0x48594f3fe29b in _cairo_pdf_surface_emit_font_subsets /gecko/gfx/cairo/cairo/src/cairo-pdf-surface.c:6668:14
    #17 0x48594f3f7060 in _cairo_pdf_surface_finish /gecko/gfx/cairo/cairo/src/cairo-pdf-surface.c:2450:11
    #18 0x48594f67f41c in _cairo_surface_finish /gecko/gfx/cairo/cairo/src/cairo-surface.c:1034:11
    #19 0x48594f67dfd0 in _moz_cairo_surface_finish /gecko/gfx/cairo/cairo/src/cairo-surface.c:1083:5

Objects leaked above:
0x6170003d1a00 (768 bytes)

A Pernosco session is available here: https://pernos.co/debug/qbq9Fg6Sn5FjOTST9Jw8OA/index.html

Probably from the cairo update? Jonathan feel free to ni? back if you don't have cycles for this and I can look.

For context here, Tyson has only recently started fuzzing for leaks, so it isn't necessarily a regression.

Looking at the test case, it seems like we're hitting some issue when we try to print a specific character.

This is already fixed upstream in https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/192; we should simply take that fix. I'll post a patch.

https://hg.mozilla.org/mozilla-central/rev/c68e5e639d01