AMD64/Intel 64 library path

[ylai]

Hi,

When I attempted to install both IA-32 and AMD64/Intel 64 versions of ROOT, I noticed that the $ROOTSYS based installation always use a hardwired lib and never lib64 (which would allow you to run binaries linked to ROOT with both bit length without switching $ROOTSYS). This behavior in fact violates the ABI standard for Linux (version 0.98, p. 119, see http://www.x86-64.org/documentation.html).

I applied a simple patch to fix this behavior. I wonder if this should be rather the default behavior for the ROOT installation.

Best,

Yue Shi Lai
root_v5.16.00-x86_64_abi.patch.txt (414 Bytes)

[cholm]

Hi,

I’m not sure what merit the referred document (x86-64.org/documentation.html) has. Although the appendix referred to specify

A.1 Execution of 32-bit Programs

The AMD64 processors are able to execute 64-bit AMD64 and also 32-bit ia32 programs. Libraries conforming to the Intel386 ABI will live in the normal places like /lib, /usr/lib and /usr/bin. Libraries following the AMD64, will use lib64 subdirectories for the libraries, e.g /lib64 and /usr/lib64. Programs conforming to Intel386 ABI and to the AMD64 ABI will share directories like /usr/bin. In particular, there will be no /bin64 directory.

but on the other hand

Chapter 2

Software Installation

This document does not specify how software must be installed on an AMD64 architecture machine.

which to me indicates that the normal Linux FHS (pathname.com/fhs/pub/fhs-2.3 … MATLIBRARI)

/usr/lib : Alternate format libraries (optional)
Purpose

/usr/lib performs the same role as /usr/lib for an alternate binary format, except that the symbolic links /usr/lib/sendmail and /usr/lib/X11 are not required.

There is thus no requirements that true-64bit libraries live in /usr/lib64.

I think that the multi-architecture question is quite confusing at the moment. Note, that I talk about multi-arch in general - the problem is not limited to i386 vs. amd64, there is also mips(el) O32, N32, N64, hppa, and so on. It seems that the general recommendation is to install libraries into /usr/gcc -dumpmachine/lib - no matter what, and then let the OS make the proper sym-links. However, no consensus seems to have emerged.

Since I know Debian best, let me comment on that. Debian always put libraries in /usr/lib, no matter whether the target architecture is a multi-architecture or not. On AMD64, there’s a sym-link from /usr/lib64 to /usr/lib to deal with ‘weird’ applications. There’s a study done (multiarch.alioth.debian.org/mult … report.pdf) for HP about multi-arch in Debian in general - it might be instructive to read.

I do not think your patch is really worth the effort. In all likeliness it will break many installations. Your change is certainly by far not enough for proper behaviour. You will have to change numerous places in the code where the library path is hard-coded, and various support scripts.

On the other hand, you can do a ‘fixed directory’ installation, specifying a multi-arch library installation directory, for example

./configure --prefix=/opt/root --libdir=/opt/root/`gcc -dumpmachine`

On my MacPRO machine (amd64) I run a i386 chroot to build i386 packages on the very fast machine (8GB, Xeon Quad-core :-), leaving my puny laptop to do other work.

So in short, I don’t think your suggestion is really a good idea.

Yours,