[Liverpool] Liverpool Digest, Vol 247, Issue 2

[Dan Lynch]

Hi Liam,

Welcome to the mailing list btw, I know we've spoken on Twitter plenty of
times. I didn't have a technical answer for your question so I thought I'd
leave it to the more qualified. Just wanted to say hello. You should come
down to a meeting and see us some time, 1st Wednesday of every month. We're
not that scary.

Good luck with the project.

See ya,

Dan



On Sat, Dec 11, 2010 at 3:02 PM, Liam Devine <dmail00 at gmail.com> wrote:

> Thanks for the responses guys.
>
>
>
>  Bob Ham <rah at bash.sh>
>
> Currently I am trying to figure out the best and most universal method
>
> of detecting the host architecture for Linux distros at runtime
>
>
> Use config.guess from GNU autotools.  Eg, on my system I can do the
> following:
>
> rah at myrtle:~$ /usr/share/automake-1.11/config.guess
> x86_64-unknown-linux-gnu
> rah at myrtle:~$ /usr/share/automake-1.11/config.guess | cut -f 1 -d -
> x86_64
>
> Note also that for your purposes, "use" will most likely mean reading
> the source.
>
>
> Dave Love
>
> Do you mean GNU/Linux?  Even if you don't think much of GNU autotools,
> I'm pretty sure you won't do better for platform information than
> config.sub/config.guess, and they're not specific to Linux-based
> systems.  The autotools have a lot of hard experience behind them, and I
> guess such questions are best asked in an autoconf forum.
>
>
>
> This has just recently been suggested to me and I am currently in the
> process of grokking it.
>
>
>
> for a couple of reasons:  To let users call out to external
>
> executables depending on the arch [2]
>
>
> I don't understand exactly what's required, but for building you don't
> normally care about the hardware, just what the tools target -- what
> width is a C long, not what's the addressing of the metal.
>
> It has been requested by users and I have seen real world examples of users
> trying to obtain this information using a number of methods, so it would be
> a nice feature to add such information and make it available to users. Users
> can have different settings for different architectures yet the information
> wanted is for a 'just the host' without a user supplying such information.
> I do not understand what you are getting at but as I am sure you are aware
> the size of a long in C is not defined by the standard yet only in relation
> to other types or using sizeof(long), minimum sizes LONG_MIN and LONG_MAX or
> figuring out which arch the system is using  ie. LP64 et al
>
>
> To set the correct location to look for libraries [3]
>
>
> I don't know why you want to, but you're on to a loser if you assume
> libraries are necessarily somewhere like /usr/lib64, and especially if
> you consider non-GNU/Linux systems.  While you can, perhaps, locate
> libraries with ldd and a sample binary, ask yourself why.
>
> This is required for users to search for the libraries and if present
> report there locations. where these are well known locations and the results
> from the ld cache.  A sample binary is something we would rather not have to
> have if it was at all possible, the problem is that Linux has no standards
> for this or that it does yet distros disregard it. lib can be 32, 64 or a
> semlink, lib32 can be present or lib64 can plus there may also be other
> 'known locations'
>
> My current thinking is the best method is to parse the output of
>
> 'uname -m' and this method has been confirmed to me that at least on
>
> one distro gives the value of a 32 bit id when a 32 bit distro is
>
> installed on a 64 bit system, which is what I am looking for.
>
>
> (In the absence of details,) that's not necessarily what's relevant,
> e.g.
>
>  $ /usr/share/misc/config.guess
>  x86_64-unknown-linux-gnu
>  $ linux32 /usr/share/misc/config.guess
>  i686-pc-linux-gnu
>
> You can't, in general, determine the target parameters with build-time
> tests; think cross-building a cross-compiler, and you may or may not
> regard `gcc -m...' as cross-compiling.
>
>
> I do not understand, the first returns information that it is 64 bits and
> the second 32. Am I missing something here? Cross compiling I currently do
> not see as a problem for most of the library as the user will have provided
> the architecture information to the library in a script, yet in the instance
> of wanting to find a library this information is a help. We can search the
> known locations and if not found and a 64 bit host try *lib64
>
>
> The current values that I have can be seen in [4]. Are there any
>
> others that are known to yourselves
>
>
> Look at GCC for a start on architectures of current interest, but it
> probably misses current ones.
>
>
> Thanks will do.
>
> Liam
>
>
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>
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