[llvm-bugs] [Bug 33815] New: Idea: Extend @available so that it can imply an upper bound too
via llvm-bugs
llvm-bugs at lists.llvm.org
Mon Jul 17 07:38:57 PDT 2017
https://bugs.llvm.org/show_bug.cgi?id=33815
Bug ID: 33815
Summary: Idea: Extend @available so that it can imply an upper
bound too
Product: clang
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Frontend
Assignee: unassignedclangbugs at nondot.org
Reporter: nicolasweber at gmx.de
CC: llvm-bugs at lists.llvm.org
(Feature idea; not important; feel free to WontFix.)
This is a somewhat common pattern:
if (@available(macos 10.10, *)) {
DoThingUsingNewAPIs()
} else {
DoThingUsingOldAPIs()
}
(e.g. here:
https://cs.chromium.org/chromium/src/content/common/quarantine/quarantine_mac.mm?l=239)
@available helps with the first half of that branch, but the implementation of
DoThingUsingOldAPIs() often has to suppress Wdeprecated-declaration (see e.g.
the above-linked file). It'd be cool if the else of an if
(@available(macos10.10)) was a "at most macOS 10.9" region, which could call
functions marked with attrib(availability(deprecated=10.10), and then in those
functions calls to deprecated functions wouldn't be emitted.
...hmm, looking more at this example, there's this comment:
// Once Chrome no longer supports macOS 10.9, this code will no longer be
// necessary. Note that LSCopyItemAttribute was deprecated in macOS 10.8, but
// the replacement to kLSItemQuarantineProperties did not exist until macOS
// 10.10.
So I think this only helps in situations where the availability annotation in
the SDK is wrong. Suppressing warnings for that is OK, I suppose.
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