Index out of range when rasterizing '|' on Source Code Pro with Freetype

[zacps]

There may be more cases to reproduce this, but this is easily repeatable:

• OS: Ubuntu 18.04
• Font: Source Code Pro (Regular)
• Char: |
• Glyph: 968
• Requested format: Rgb24
• Code: Add fontkit as a render backend alacritty/alacritty#1720

Complete backtrace

thread 'main' panicked at 'index 89 out of range for slice of length 88', src/libcore/slice/mod.rs:2349:5
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:59
             at src/libstd/panicking.rs:210
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:225
   4: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:488
   5: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:395
   6: rust_begin_unwind
             at src/libstd/panicking.rs:322
   7: core::panicking::panic_fmt
             at src/libcore/panicking.rs:95
   8: core::slice::slice_index_len_fail
             at src/libcore/slice/mod.rs:2349
   9: <core::ops::range::Range<usize> as core::slice::SliceIndex<[T]>>::index
             at /rustc/96d1334e567237b1507cd277938e7ae2de75ff51/src/libcore/slice/mod.rs:2514
  10: core::slice::<impl core::ops::index::Index<I> for [T]>::index
             at /rustc/96d1334e567237b1507cd277938e7ae2de75ff51/src/libcore/slice/mod.rs:2331
  11: font_kit::canvas::Canvas::blit_from_with
             at /home/zac/projects/font-kit/src/canvas.rs:153
  12: font_kit::canvas::Canvas::blit_from
             at /home/zac/projects/font-kit/src/canvas.rs:89
  13: font_kit::loaders::freetype::Font::rasterize_glyph
             at /home/zac/projects/font-kit/src/loaders/freetype.rs:754
  14: <font::fontkit::FontKitRasterizer as font::Rasterize>::get_glyph
             at font/src/fontkit/mod.rs:144
  15: alacritty::renderer::GlyphCache::get::{{closure}}
             at src/renderer/mod.rs:276
  16: <std::collections::hash::map::Entry<'a, K, V>>::or_insert_with
             at /rustc/96d1334e567237b1507cd277938e7ae2de75ff51/src/libstd/collections/hash/map.rs:2695
  17: alacritty::renderer::GlyphCache::get
             at src/renderer/mod.rs:273
  18: alacritty::renderer::GlyphCache::load_glyphs_for_font
             at src/renderer/mod.rs:204
  19: alacritty::renderer::GlyphCache::new
             at src/renderer/mod.rs:195
  20: alacritty::display::Display::new_glyph_cache::{{closure}}
             at src/display.rs:250
  21: alacritty::renderer::QuadRenderer::with_loader
             at src/renderer/mod.rs:713
  22: alacritty::display::Display::new_glyph_cache
             at src/display.rs:250
  23: alacritty::display::Display::new
             at src/display.rs:156
  24: alacritty::run
             at src/main.rs:127
  25: alacritty::main
             at src/main.rs:79
  26: std::rt::lang_start::{{closure}}
             at /rustc/96d1334e567237b1507cd277938e7ae2de75ff51/src/libstd/rt.rs:74
  27: std::panicking::try::do_call
             at src/libstd/rt.rs:59
             at src/libstd/panicking.rs:307
  28: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:102
  29: std::rt::lang_start_internal
             at src/libstd/panicking.rs:286
             at src/libstd/panic.rs:398
             at src/libstd/rt.rs:58
  30: std::rt::lang_start
             at /rustc/96d1334e567237b1507cd277938e7ae2de75ff51/src/libstd/rt.rs:74
  31: main
  32: __libc_start_main
  33: _start

---

Logging values in the loop:

Start 0 width 3 bytes 3 len 88
Start 8 width 3 bytes 3 len 88
Start 16 width 3 bytes 3 len 88
Start 24 width 3 bytes 3 len 88
Start 32 width 3 bytes 3 len 88
Start 40 width 3 bytes 3 len 88
Start 48 width 3 bytes 3 len 88
Start 56 width 3 bytes 3 len 88
Start 64 width 3 bytes 3 len 88
Start 72 width 3 bytes 3 len 88
Start 80 width 3 bytes 3 len 88
<panic 89 out of range>

[zacps]

Also occurs using DejaVu Sans Mono, glyph 77 char j.

[evilpie]

I tried to reproduce this using the render-glyph example/tool and it didn't crash.

[pcwalton]

Neither of these crash for me, so I'm closing. Feel free to reopen if you have a test case.