how to decrease link time

[baibaichen]

i know that pImpl idiom can decrease compile time, but Is there any
good practice/idiom to decrease link time?

any reference or any idea is appreciated

thanks

[baibaichen]

imagine that I am sitting at my desk fixing bugs all day long. When I
make a change and build, how many files are going to compile? 3? 10?
100? My guess is that over a whole day, each build will compile maybe
five files on average. Only rarely will I make a change to some header
file that causes more than 100 files to be recompiled. How long does it
take five files to compile? On my laptop, which is over a year old,
five files will compile in less than 30 seconds, and often in less than
10 seconds. Now consider link times: on my laptop, it takes about 12
minutes for DVDit to link, even if only one source file was changed.

Even if I were compiling 50 files, that's still less than five minutes,
and often less than two minutes. I wonder how much you could actually
reduce that by using relative paths.

[Alf P. Steinbach]

* baibaichen:

i know that pImpl idiom can decrease compile time, but Is there any
good practice/idiom to decrease link time?

Yes, the same as in general programming: divide and conquer.

If you're linking some hundreds of object files you have packaging problem:
repackage in smaller libraries (this may require some redesign; packaging
can affect design and vice versa). Use the appropriate options and/or tools
to optimize your libraries for fast access. E.g., under *nix, run 'ranlib'.

If you're linking some hundreds of libraries you also have a packaging
problem: repackage in smaller executables and dynamic libraries (this may
require some redesign; packaging can affect design and vice versa).

Of course this has only tangentially to do with current C++ as a language.

But, to the degree usage of the language is affected and hindered by tool
usage I think at least this kind of high level advice is on-topic. However,
be aware that concrete tool usage issues are rarely or not ever on-topic in
this group. This group is concerned with the C++ _language_.

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[Stephan Brönnimann]

Are you using libraries (shared?) or do you just link all object files?
Just a wild guess: I suspect the system starts trashing when you link.
Monitor the disk I/O, memory and swap space usage.

regards, Stephan