[gentoo-dev] Re: [gentoo-dev-announce] debug USE flag misuse

[Vaeth]

Ryan Hill <dirtyepic@g.o> wrote:

> If your build system sets -ffast-math or -fstrict-aliasing
> then the user can disable this by setting -fno-fast-math
> or -fno-strict-aliasing in their CFLAGS.

Just because some flags have "counter"-flags by accident,
this does not hold for all flags. It is more reasonable to have
other means that the flags are not modified in the first place.
In fact, when I first introduced adding of CFLAGS, there were
lot of complaints that this is evil and must not be done.
I can understand this point of view (even if I know that
certain CFLAGS should be used with the code and I would also
prefer to have them to find possibly hidden bugs), so we
compromised by having an option:
With this option everybody could live well, since users with
special settings will not run into trouble because undesired
flags are added, and other users could just select the USE flag
and have the benefits of appropriately optimized code.
Up to now, that is, when we have this IMHO needless discussion
that an option should not be an option.

I hope that this answers also the question of
Alec Warner <antarus@g.o>:

: I am confused.  If you want the users to use a default set of CFLAGS
: you should set this in your build system (autotools, cmake, whatever).
: [...]
: I believe the above link seems to describe what you are looking to do
: using autotools.

Technically, I have no problem to force in configure.ac that certain
CFLAGS are used (unless somebody patches the configure.ac, of course).
The problem is that it is not good to force this if the user disagrees
(or maybe even unless he explicitly agrees), i.e. it should be an
option which the user really has. (If this option should only be
documented in some INSTALL text or in the ./configure output,
most users do not really have this option, because they would not
even know about it.)

Best Regards
Martin