[Scons-dev] Accommodating dependency cycles.

[Gary Oberbrunner]

On Wed, Mar 22, 2017 at 10:47 PM, William Blevins <wblevins001 at gmail.com>
wrote:

> Here is another one. I assume this round of issues is because they updated
> SCons on the latest Ubuntu. This one actually makes sense. Someone else
> posted this one. "test2.h" explicitly depends on "test.h" via Command
> Builder, and "test.h" implicitly depends on "test2.h" via scanner.


except not quite: the scanner makes (or *should* make) anything *compiled
from* test.h (e.g. test.obj) depend on test2.h. test.h has no dependencies;
it's a source. As perhaps you noted above, it seems like the Command
builder is somehow running the C scanner, but shouldn't. If the Command in
this example had been an Object or Program whose target was still called
test2.h, then there would be a real dependency loop (because test.h
includes test2.h, SCons shouldn't compile test.h into the result object
until test2.h is up-to-date, and the result "object file" in that case is
called test2.h).

-- 
Gary
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