Why is CFLAGS sometimes ignored?

[extraketchup]

In building my Gentoo system, I notice sometimes that the CFLAGS being pased to gcc / g++ do not match what I have for flags. For example, installing QT seems to use O2 whereas I prefer to use the Os compile option (personal preference).

I assume that an ebuild can override CFLAGS for some reason (safe builds?). Can I override the override? I don't mind "taking the risk" since Os should not be as risky as O3. How do I make sure my CFLAGS are used regardless?

Thanks for your help!!

Mike

[rmalolepszy]

I think this thread sums it up quite well.

https://forums.gentoo.org/viewtopic.php?t=169132&highlight=cflags+qt
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Cheers,
Ryan