PR# 19160 Compiling hangs at end of degree 4 with AutoTest libraries added

Problem Report Summary
Submitter: axarosenberg
Category: Compiler
Priority: Low
Date: 2015/11/26
Class: Bug
Severity: Serious
Number: 19160
Release: 15.01
Confidential: No
Status: Analyzed
Environment: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36
Synopsis: Compiling hangs at end of degree 4 with AutoTest libraries added

I wanted to try out AutoTest's test extraction feature, but I only got as far as saying 'Yes' to the dialog that asked me if I wanted the testing library added and the project recompiled.
The compile seemed to hang at the end of degree 4, with one CPU 100% busy, and working set size steadily rising (above 3.2GB) according to Task Manager.
So I deleted the EIFGENs and re-compiled from scratch. The same thing happened.
So I had to remove the testing library and re-compile from scratch again. This time the compile worked OK.
To Reproduce
See the description.
Problem Report Interactions
From:axarosenberg    Date:2015/12/04    Download   
It happened again today, but as CPU was 100% I waited for a while - eventually it completed.

From:axarosenberg    Date:2015/11/26    Download   
but all classes compile fine without the testing library added.

From:manus_eiffel    Date:2015/11/26    Status: Analyzed    Download   
This is indeed the side effect of using the testing library in a project, it will have to compile all classes to find test cases. I'll keep this bug open as this is something that should be better optimized.

From:axarosenberg    Date:2015/11/26    Download   
This appears to be related to the size of the code-base. The problem occurred with something like 20,000 classes in the codebase.

I tried again with just the base and testing libraries, and a cluster of four small classes. This compiles OK.