Compile Imported Modules

[H. S. Teoh via Digitalmars-d]

On Thu, Aug 24, 2017 at 06:00:15PM +0000, Jonathan Marler via Digitalmars-d wrote:
> On Thursday, 24 August 2017 at 17:49:27 UTC, H. S. Teoh wrote:
> > Uh, no.  This will definitely break separate compilation, and some
> > people will be very unhappy about that.
> 
> I couldn't think of a case that it would break.  Can you share the
> cases you thought of?

Suppose you have main.d and module.d, and you want to compile them
separately:

	dmd -c main.d
	dmd -c module.d
	dmd -ofmyprogram main.o module.o

If dmd defaulted to auto-importing, then `dmd -c main.d` would also
compile module.d (assuming main.d imports `module`), contrary to what
was intended in a separate compilation scenario, and the last command
will produce a linker error from duplicated symbols.

This is just a simple case, of course. But in general, changing the
meaning of `dmd -c source.d` will break existing build scripts.  Sure,
you could ask people to update their build scripts to include
`-no-auto-imports`, but that requires effort from users, who will be
unhappy that upgrading dmd broke their build scripts.  For large
projects, such a change may not be trivial as in the above example.


T

-- 
Life is too short to run proprietary software. -- Bdale Garbee