Re: About libdir for 64-bit

[Russ Allbery]

Ralf Corsepius <address@hidden> writes:
> On 07/18/2013 10:07 AM, Thomas Jahns wrote:
>> On 07/17/13 22:11, Russ Allbery wrote:

>>> Probing sizeof(long) with the configure compiler does a fairly good
>>> job for the most common cases, which is why that's what the macro I
>>> posted does.  In particular, it works for the common cases of -m32 and
>>> -m64 on hosts with both library paths.

>> How does that distinguish x32 and i386? Or the n32 and o32 formats on
>> IRIX?

> No. When being used alone, it only distinguishes targets using 64 longs
> from targets using other sizes of long. Anything else is
> overinterpretation.

> However, combining sizeof(long) with other cpp defines can be utilized
> to distinguish archs. In most cases this isn't necessary, because
> compilers usually provide specialized arch/ABI-specific internal defines
> which better suite such needs.

> Unfortunately, I am not sufficiently familiar with the x32 archs and
> IRIX to be more specific.

Thomas originally sent his message privately so I responded privately.
I'll include my reply here; the short version is that those variations
don't use the same lib{32,64} scheme, and my macro was only trying to cope
with that one variation.

Anyway, my note:

It doesn't -- but neither of those use the lib64/lib32 layout either,
because that layout can't represent that difference.  They do something
more complicated (they have to).  So basically it's out of scope for what
my macro is trying to solve (and what the original question asked for,
also).

I personally think the Debian approach of not using lib32/lib64 at all and
intead adding a full triplet to qualify the library directory is the
superior approach, but as Wookey notes, there's no current Autoconf
support for handling that automatically.  Debian's build system uses
--libdir to set the directory with distribution knowledge of the correct
value.

-- 
Russ Allbery (address@hidden)             <http://www.eyrie.org/~eagle/>