[gentoo-user] USE="custom-optimization"

[Florian Philipp]

Hi list!

I'm wondering how to interpret the custom-optimization use flag which
has become much more common in the recent weeks/months.

I mean, I understand the basic concept: it either uses the cflags from
my make.conf or its own set. But what exactly does the dev want to tell
me when she uses this flag and sets it to default off?

1. "If you have a fancy set of uncommon cflags, this package might break
in funny ways. Therefore you might want to use my set of conservative
flags instead."

2. "In order to run perfectly, this package needs a very unique set of
cflags. Trust me to set them properly if you have a rather common system."

3. "No one will give you support when this package breaks unless you use
the default compile flags. However, for optimal performance you might
still want to use your own set of flags."

I'm asking because very different packages have started using this flag,
for example Firefox and ffmpeg. For Firefox, I'd think the dev thought
of 1 or 3. With ffmpeg, number 2 might be the right interpretation,
especially as it seems to set such uncommon flags as -O3 (which always
decreased performance when I tried it for other packages or my own
programs).

Just for the records: I'm using a conservative set of cflags:
-march=core2 and -O2