On 3/26/19 5:25 PM, Ken Moffat via blfs-dev wrote:
On Tue, Mar 26, 2019 at 02:55:40PM -0500, Bruce Dubbs via blfs-dev wrote:
I suppose libdrm, gdk-pixbuf, glib2, pango might be interesting
packages to look at.
As an initial guess, I think I should compare (with 4 cores) :
· the book's current build
· forcing a release
· forcing a release but passing CFLAGS, CXXFLAGS of just '-g'
Does that sound sensible ?
Seems like an interesting experiment. You don't really have to install,
just build.
I have little experience using gdb, I'm
not entirely convinced that trying to debug a -O3 build would ever
be useful.
I agree. -O3 removes a lot of code through things like inlining and
changes a lot with things like loop unrolling. Generally I think that a
lot of optimization is unneeded unless a profile is done and critical
sections optimized.
The default in Mesa uses -O2 -g but also enables the
assertions, maybe a release with -O2 -g would be more useful ?
I suspect it would be cleaner.
I also start to wonder if we ought to expand 'Notes on Building
Software' with a section about optimizations ?
A reasonable suggestion.
We used to only have
to really care about CMMI packages, with CFLAGS and CXXFLAGS - some
of those ignore the flags, and for those which accept them we assume
experienced builders will know about the obvious -O, -O2, -O3, -g.
But with (I think) both cmake and meson we perhaps need to spell out
somewhere what the typical defaults are ? (as well as maybe
specifying release builds, perhaps with notes about what that
actually does).
We can get into a lot of discussion there.
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
And then there are linking options to consider.
https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html
How much do you think is reasonable?
-- Bruce
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