|
This method is called from multiple threads in a parallel build,
so only do thread safe stuff here. Do thread unsafe stuff in
built().
Note that there's a special trick here with the execute flag
(one that's not normally done for other actions). Basically
if the user requested a no_exec (-n) build, then
SCons.Action.execute_actions is set to 0 and when any action
is called, it does its showing but then just returns zero
instead of actually calling the action execution operation.
The problem for caching is that if the file does NOT exist in
cache then the CacheRetrieveString won't return anything to
show for the task, but the Action.__call__ won't call
CacheRetrieveFunc; instead it just returns zero, which makes
the code below think that the file was successfully
retrieved from the cache, therefore it doesn't do any
subsequent building. However, the CacheRetrieveString didn't
print anything because it didn't actually exist in the cache,
and no more build actions will be performed, so the user just
sees nothing. The fix is to tell Action.__call__ to always
execute the CacheRetrieveFunc and then have the latter
explicitly check SCons.Action.execute_actions itself.
|