Our template emission strategy is broken

[Martin Nowak via Digitalmars-d]

On Wednesday, 11 November 2015 at 14:15:54 UTC, Johannes Pfau 
wrote:
> And where do you draw the line? Do we expect ARM users to have 
> 4GB of RAM to compile phobos? Is 512MB enough? 64 MB? Even huge 
> C++ codebases such as GCC compile with 128MB memory.

OK let's clarify the terminology first.

separate compilation: -c single_source.d
incremental compilation: -c source_a.d source_b.d (as well as -c 
-ofsingle.o source_a.d source_b.d)
library compilation: -lib all_pkg_sources

Separate compilation works fine (and predictable) but is slow 
(due to reparsing), you do need to link all objects from all your 
sources though.
Choosing this strategy makes sense to mitigate OOM issues.

Incremental compilation doesn't work b/c templates are easily 
emitted into different objects, causing all sorts of linker 
errors. It works somewhat when you delete all objects and 
recompile all of them.

Library compilation works and recompiles a whole library whenever 
something changes.
It's fast b/c modules/semantic can be reused by the compiler.
Choose this strategy unless your running into OOM issues.