Commit Graph

2 Commits

Author SHA1 Message Date
Nathan James e1c729c568
[clang-tidy][NFC] Update tests and Default options to use boolean value
Change instances where options which are boolean are assigned the value 1|0 to use true|false instead.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D101721
2021-05-04 18:17:56 +01:00
Roman Lebedev 46b8ea2fff
[clang-tidy] Add check for implicit widening of multiplication result
Overflows are never fun.
In most cases (in most of the code), they are rare,
because usually you e.g. don't have as many elements.

However, it's exceptionally easy to fall into this pitfail
in code that deals with images, because, assuming 4-channel 32-bit FP data,
you need *just* ~269 megapixel image to case an overflow
when computing at least the total byte count.

In [[ https://github.com/darktable-org/darktable | darktable ]], there is a *long*, painful history of dealing with such bugs:
* https://github.com/darktable-org/darktable/pull/7740
* https://github.com/darktable-org/darktable/pull/7419
* eea1989f2c
* 70626dd95b
* https://github.com/darktable-org/darktable/pull/670
* 38c69fb1b2

and yet they clearly keep resurfacing still.

It would be immensely helpful to have a diagnostic for those patterns,
which is what this change proposes.

Currently, i only diagnose the most obvious case, where multiplication
is directly widened with no other expressions inbetween,
(i.e. `long r = (int)a * (int)b` but not even e.g. `long r = ((int)a * (int)b)`)
however that might be worth relaxing later.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D93822
2021-04-13 21:41:22 +03:00