assume, assert, enforce, @safe

[Daniel Murphy via Digitalmars-d]

"Johannes Pfau"  wrote in message news:lrgar7$1vrr$1 at digitalmars.com...

> Do you know if linkers actually guarantee that behaviour? AFAICS dmd
> doesn't do anything special, it always emits weak symbols and just calls
> gcc to link. The linker usually uses the first symbol it sees, but I
> have not seen any guarantees for that.

Yes, they do.  Or at least, it's the classic linker behaviour and I expect 
they all implement it.  It's relied upon for nofloat and a few other things. 
It's one of the reasons linkers are hard to parallelize.

dmd does split single d modules into multiple object modules when compiling 
with -lib, although I think that's fairly standard.

> Also what happens if your main application doesn't use the template,
> but two libraries use the same template. Then which instances are
> actually used? I'd guess those from the 'first' library?

Well, the first one that it encounters after getting the undefined 
reference.

eg
module application
{
undef x
...
}


lib1:
module a
{
undef tmpl
def a
}
module tmpl
{
def tmpl
}

lib2:
module x
{
undef tmpl
def x
}
module tmpl
{
def tmpl
}

Here nothing that the application references will cause the tmpl in lib1 to 
get pulled in, but when it processes lib2 it will pull in x, and then tmpl.