1540357 - Force -Werror for implicit int truncation for dom/canvas

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, enhancement, P3)

Description

[Kelsey Gilbert [:jgilbert]]

We do a lot of validation, and we really don't want C++ truncating values behind our backs.

Comment 1

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Add AutoAssertCast to auto-infer the type for AssertedCast.

Comment 2

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Force -Werror for and fix implicit int truncation in dom/canvas.

Depends on D25494

Comment 3

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int truncation dom/canvas's js/* includes.

Depends on D25495

Comment 4

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int truncation in dom/canvas's dom/* includes.

Depends on D25496

Comment 5

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int truncation in dom/canvas's gfx/* includes.

Depends on D25497

Comment 6

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int conversions in dom/canvas's layout/* includes.

Depends on D25498

Comment 7

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int truncation in dom/canvas's xpcom/* includes.

Depends on D25499

Comment 8

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1540357 - Fix implicit int truncation in dom/canvas's mfbt/* includes.

Depends on D25500

Comment 9

[Daniel Holbert [:dholbert]]

It looks like you're using C-style casts, i.e.
return (uint8_t)foo;
...or
return uint8_t(expression);

Given that we're now following Google's C++ coding style (per red-background note at old Mozilla Coding Style page), perhaps these should really be using static_cast<uint8_t>(...) (or uint8_t{...}) instead?

See this particular guideline:

Do not use C-style casts. Instead, use these C++-style casts when explicit type conversion is necessary.

• Use brace initialization to convert arithmetic types (e.g. int64{x}). This is the safest approach because code will not compile if conversion can result in information loss. The syntax is also concise.
• Use static_cast as the equivalent of a C-style cast that does value conversion, when you need to explicitly up-cast a pointer from a class to its superclass, or when you need to explicitly cast a pointer from a superclass to a subclass. In this last case, you must be sure your object is actually an instance of the subclass.

https://google.github.io/styleguide/cppguide.html#Casting

Comment 10

[Kelsey Gilbert [:jgilbert]]

I suppose so, though last time I asserted that we should follow Google C++ style, I was rebuffed in favor of existing style! My understanding is that we've only adopted the Google C++ /whitespace/ style thus far.

Also, static_cast<>() might have the worst ergonomics in the world.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/08d7c5e08995
Force -Werror for and fix implicit int truncation in dom/canvas. r=lsalzman
https://hg.mozilla.org/integration/autoland/rev/89552599db42
Fix implicit int truncation dom/canvas's js/* includes. r=sfink
https://hg.mozilla.org/integration/autoland/rev/54a2f08bcf48
Fix implicit int truncation in dom/canvas's dom/* includes. r=qdot
https://hg.mozilla.org/integration/autoland/rev/f4debce94b00
Fix implicit int truncation in dom/canvas's gfx/* includes. r=jrmuizel
https://hg.mozilla.org/integration/autoland/rev/c941cc70ee3e
Fix implicit int conversions in dom/canvas's layout/* includes. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/54d64288d7de
Fix implicit int truncation in dom/canvas's xpcom/* includes. r=mccr8
https://hg.mozilla.org/integration/autoland/rev/093c37e856fb
Fix implicit int truncation in dom/canvas's mfbt/* includes. r=froydnj

Comment 12

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/08d7c5e08995
https://hg.mozilla.org/mozilla-central/rev/89552599db42
https://hg.mozilla.org/mozilla-central/rev/54a2f08bcf48
https://hg.mozilla.org/mozilla-central/rev/f4debce94b00
https://hg.mozilla.org/mozilla-central/rev/c941cc70ee3e
https://hg.mozilla.org/mozilla-central/rev/54d64288d7de
https://hg.mozilla.org/mozilla-central/rev/093c37e856fb