Why doesn't DMD create any redundant symbols?

[Walter Bright]

Gregor Richards wrote:
> I have to assume there's a reason for this, so, to summarize: Why 
> doesn't DMD create any redundant symbols in .o files?

It can improve build speed a lot. With C++, which doesn't do this, huge 
.obj files can be generated.

The compiler assumes that if there are multiple modules on the command 
line, they'll all be linked together, so why generate redundant output?