RFC: naming, dll versions and installing

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-12-09 04:30:32

Hi,
there's a design question that I'd like to discuss. It's related to "install" 
support for Boost.

Sometimes, the names of installed libraries must follow special convention. 
One example is encoding library version in name (very common on Unix). 
Another is encoding build variant in name (used in Boost, some other 
libraries have single-thread and mt variants). However, on Linux, change of 
library names requires relinking, you can't just copy a file.

What's worse, if libA uses libB, you need to use relinked libB when relinking 
libA, which means the sources of libA must be also changed.

Now, there's another approach, but I can't decide which is best.

Approach 1. Relinking. The naming convention is specified on the stage rule 
using the <so-version> and <tag> features:

lib a : a.cpp ;
stage dist : a : 
<so-version>1.32.0 <tag>@stage.encode-variant-and-compiler ;

this requires relinking

Approach 2. Always using the same names:

lib a : a.cpp :
<so-version>1.32.0 <tag>@stage.encode-variant-and-compiler ;
stage dist : a ;

There are couple of use cases.

Use case 1: single naming scheme. Suppose that a single naming scheme is 
always used by a project.

Advantages of approach 2: no relinking, so somewhat faster. 
Disadvantages of approach 2:
- The additional properties must be specified for every library. 
- The names of libraries will be longer even when not installing,
and we have long names already.

Use case 2: several naming schemes. For example, boost has two variants of 
library naming for install.

Additional disadvantages of approach 2:

- The obvious solution is that top-level Jamfile will compute proper
properties and store them in variable TAG. Each lib will be defined as:

lib a : a.cpp : $(TAG) ;

In this case, it won't be possible to install with two naming conventions
at the same time.

- After building with a different naming convention, the tree will contain
several versions of each library (one for each naming convention)

Can anyone comment? Do we need stage to be able to change the names of 
libraries and relink them? 

- Volodya