On Wed, Feb 23, 2011 at 11:15:02PM +0100, Philipp Kern wrote: > On Wed, Feb 23, 2011 at 01:52:35PM -0800, Steve Langasek wrote: > > [1] i486 is an arbitrary name that happens to correspond to the base > > instruction set that was in use on Debian at the time multiarch was first > > formulated, but it doesn't match the current base instruction set on Debian > > (i586) or Ubuntu (i686), doesn't match the directory configured in the > > current eglibc package on Ubuntu (/lib/i686-linux-gnu), and is going to look > > weird to other distributions when we try to talk to them about this since > > they've also long since moved to i686 as their base compatibility. > Sorry to skip multiarch[1], but I need to comment on this one. Isn't the > base instruction set still i486? I still haven't found any practical > example of a change of ISA between i486 and i586. For all means they seem > to be equivalent, with i686 being the next break. The only exception that > might be is that 486 can actually lack FPUs, while Pentiums don't. But > for all practically relevant cases I'd assume that they don't, and I'd be > surprised if we'd cater for that. Ah, I don't know the details; I take this as gospel from the GCC maintainers that There Are Differences. Perhaps the differences are only optimization rather than compatibility; but regardless, given that most distros use i586-linux-gnu or i686-linux-gnu as their toolchain triplet, i486-linux-gnu is an odd bird to propose to standardize on. > Out of curiosity: Where will optimized libraries be placed? Multiarch can be combined transparently with hwcaps; so you can have /lib/i386-linux-gnu/i686/cmov/, /lib/alpha-linux-gnu/ev67/, etc. Multiarch also does not require that the libraries installed to the base directory are backwards-compatible with anything that you don't care about, so it's fine to have i686 libraries directly in /lib/i386-linux-gnu on a distro whose baseline is i686, while they're in a hwcap directory for another distro. > [1] As you said pre-depends are messy but the safe bet. It would be best if > we could somehow ensure that libc6 is upgraded first and that everything > needed for the unpack is still there at that point (i.e. some liberal > use of pre-depends somewhere in just the base set instead of everywhere). Ok. I think that's certainly going to be more manageable than trying to add pre-depends to everything, anyway. Any concerns about bumping the dependency for all libraries via dpkg-shlibdeps? -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ slangasek@ubuntu.com vorlon@debian.org
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