1624776 - Replace MOZ_MUST_USE with [[nodiscard]] in xpcom

Status: RESOLVED FIXED

(Core :: XPCOM, task, P3)

Description

[Chris Peterson [:cpeterson]]

The MOZ_MUST_USE macro is defined as clang's and gcc's nonstandard attribute((warn_unused_result)). Now that we compile as C++17 by default (bug 1560664), we can replace MOZ_MUST_USE with C++17's standard [[nodiscard]] attribute.

Also move MOZ_MUST_USE before function declarations' specifiers and return type. While clang and gcc's __attribute__((warn_unused_result)) can appear before, between, or after function specifiers and return types, the [[nodiscard]] attribute must precede the function specifiers.

Also remove MOZ_MUST_USE from nsIMemoryReporter's function pointer typedefs. [[nodiscard]] is an attribute of a function's declaration, not the function's type, and thus can't be applied to function pointers or lambdas.

Comment 1

[Chris Peterson [:cpeterson]]

Attachment: Bug 1624776 - Replace MOZ_MUST_USE with [[nodiscard]] in xpcom. r?KrisWright

Also move MOZ_MUST_USE before function declarations' specifiers and return type. While clang and gcc's attribute((warn_unused_result)) can appear before, between, or after function specifiers and return types, the [[nodiscard]] attribute must precede the function specifiers.

Also remove MOZ_MUST_USE from nsIMemoryReporter's function pointer typedefs. [[nodiscard]] is an attribute of a function's declaration, not the function's type, and thus can't be applied to function pointers or lambdas.

Comment 2

[Chris Peterson [:cpeterson]]

I revised my patch to fix the indentation defects reported by reviewbot.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d87c15bc2a08
Replace MOZ_MUST_USE with [[nodiscard]] in xpcom. r=xpcom-reviewers,KrisWright

Comment 4

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/d87c15bc2a08