Bug 875578

Summary:	flag-o-matic.eclass: strip-unsupported-flags tests flags one at a time, which fails with flags that depend on other flags
Product:	Gentoo Linux	Reporter:	marios4
Component:	Eclasses	Assignee:	Gentoo Toolchain Maintainers <toolchain>
Status:	UNCONFIRMED ---
Severity:	normal	CC:	erikdenstore+gbugs, gentoo
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---

Description marios4 2022-10-06 08:27:57 UTC

When a flags requires another flag (for example clang -fwhole-program-vtables requires -flto) it gets stripped even if the requirement is met. This happens because each flag is tested independently. Maybe the easiest way to fix it is by patching the compiler to just ignore those flags when the requirement is not met (or emit a warning instead of an error).

Comment 1 eroen 2025-03-18 18:24:07 UTC

This also causes problems with *FLAGS generated by `resolve-march-native --clang`. As of version 6.0.1, rmn generates something like this:

    -march=sandybridge -Xclang -target-feature -Xclang +64bit -Xclang -target-feature -Xclang +aes

which gets filtered into something invalid like this:

    -march=sandybridge -Xclang -Xclang -Xclang -Xclang