1363907 - store_bytes.h:60:27 [-Wunused-value] expression result unused

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Daniel Holbert [:dholbert]]

Just noticed this build warning in my buildspew:
> store_bytes.h:60:27 [-Wunused-value] expression result unused

tl;dr: this is from a line of cruft that was mistakenly left behind in bug 1322660.


Details
=======
The warning points to the final line of the following enigmatic chunk of code:
>  uint16_t v = ((val & 0xFF) << 8) | ((val & 0xFF00) >> 8);
>  memcpy(dst + *offset, &v, 2);
>       ((val & 0xFF) << 8) | ((val & 0xFF00) >> 8);
https://dxr.mozilla.org/mozilla-central/rev/ebbcdaa5b5802ecd39624dd2acbdda8547b8384d/modules/woff2/src/store_bytes.h#60

Indeed, that final line is simply some arithmetic which is unused!

Before bug 1322660, it looked like this:
>   *reinterpret_cast<uint16_t*>(dst + *offset) =
>       ((val & 0xFF) << 8) | ((val & 0xFF00) >> 8);

Bug 1322660 replaced this assignment with a memcpy operation, but left the "((val & 0xFF)" etc. expression standing alone, doing nothing:
https://hg.mozilla.org/mozilla-central/diff/1c8f82fbc5cf/modules/woff2/src/store_bytes.h#l1.39

fredw: if I'm understanding correctly, could you take this & remove that line?

Comment 1

[Frédéric Wang (:fredw)]

(In reply to Daniel Holbert [:dholbert] (AFK May 3-8, 13-21) from comment #0)
> Bug 1322660 replaced this assignment with a memcpy operation, but left the
> "((val & 0xFF)" etc. expression standing alone, doing nothing:
> https://hg.mozilla.org/mozilla-central/diff/1c8f82fbc5cf/modules/woff2/src/
> store_bytes.h#l1.39

Right, that's how I see it too.

> 
> fredw: if I'm understanding correctly, could you take this & remove that
> line?

Sure, will try it when I have time.

Comment 2

[BMO Automation]

Per policy at https://wiki.mozilla.org/Bug_Triage/Projects/Bug_Handling/Bug_Husbandry#Inactive_Bugs. If this bug is not an enhancement request or a bug not present in a supported release of Firefox, then it may be reopened.

Comment 3

[Daniel Holbert [:dholbert]]

This was fixed in https://hg.mozilla.org/mozilla-central/rev/0dc9284b03d4#l11.53 (bug 1384862)