[fpc-other] What makes a Compiler project (like FPC) special?

[Graeme Geldenhuys]

This is directed at Florian primarily, but any other FPC core member is 
welcome to chip in.

Since Florian mentioned that a compiler project is "rocket science" [not 
his direct words, but he hinted at that] and totally different to any 
other software project... It has really bugged me... Why is it 
different, and What is different?

 From the recent comments in this mailing list by Sven, Marco and Karoly 
I got a bit more insight... mainly things like CI (continuous 
integration) and automated builds and test suites, testing on various 
platforms etc.

Still, that doesn't make a compiler project that special to me. eg: The 
tiOPF project runs automated builds every 3 hours with its test suite. 
Those are totally clean builds using the latest source code. Those 
builds run under Linux, FreeBSD and Windows. They also have different 
combination of options, testing various persistence layers (Zeos+MySQL, 
Zeos+Firebird, SqlDB+MySQL, SqlDB+Firebird, SqlDB+PostgreSQL, IBX, 
Oracle to name but a few). Even different compilers FPC 2.6.4, FPC 3.0.2 
and Delphi 7 (we don't have access no later Delphi versions any more). 
Tests alone take between 20-30 minutes to run. All build results are 
stored and can later be reviewed. The latest summary results are posted 
to a "builds" newsgroup with a URL to a website for a full review of 
each test case (1800+ tests) with the exact errors, line numbers etc.

So, what makes a compiler project like FPC different to that?

Regards,
   Graeme