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| author | David Benjamin <davidben@google.com> | 2024-03-24 19:43:58 -0400 |
|---|---|---|
| committer | David Benjamin <davidben@google.com> | 2024-03-24 20:00:01 -0400 |
| commit | 8a7ecd774c4032f30949665b42910c2d2cae53f2 (patch) | |
| tree | 1a2f955d0570cd592703c96ef01890a997af005e /egl | |
| parent | protocol: document that color channels provide electrical values (diff) | |
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util: fix undefined behavior in wl_array_for_each
If a wl_array has size zero, wl_array_for_each computes NULL + 0 to get
to the end pointer. This should be fine, and indeed it would be fine in
C++. But the C specification has a mistake here and it is actually
undefined behavior. See
https://davidben.net/2024/01/15/empty-slices.html
Clang's -fsanitize=undefined flags this. I ran into this in Chromium's
build with wayland-scanner on one of our XML files.
../../third_party/wayland/src/src/scanner.c:1853:2: runtime error: applying zero offset to null pointer
#0 0x55c979b8e02c in emit_code third_party/wayland/src/src/scanner.c:1853:2
#1 0x55c979b89323 in main third_party/wayland/src/src/scanner.c
#2 0x7f8dfdb8c6c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#3 0x7f8dfdb8c784 in __libc_start_main csu/../csu/libc-start.c:360:3
#4 0x55c979b70f39 in _start (...)
An empty XML file is sufficient to hit this case, so I've added it as a
test. To reproduce, undo the fix and include only the test, then build
with:
CC=clang CFLAGS="-fno-sanitize-recover=undefined" meson build/ -Db_sanitize=undefined -Db_lundef=false
ninja -C build test
Signed-off-by: David Benjamin <davidben@google.com>
Diffstat (limited to 'egl')
0 files changed, 0 insertions, 0 deletions