On Tue, 12 Mar 2013 03:31:30 -0400, Lars T. Kyllingstad
<[email protected]> wrote:
Nice catch! Fortunately, the only bug here is that I've specified a
null parameter in the spawn call in pipeProcessImpl(). If you look at
the various spawnProcess() overloads, you'll see that they are designed
as follows:
If you omit the AA parameter altogether, the child inherits the parent's
environment. A null pointer is passed as 'envz' to spawnProcessImpl(),
which in turn passes this straight to CreateProcess() on Windows and
replaces it by 'environ' on POSIX.
If you do specify the AA parameter, it is passed through toEnvz() on its
way to spawnProcessImpl(). If the AA is empty/null, toEnvz() will
create an empty (but non-null) environment block, and the child's
environment will be empty.
I understand that point. I am a little concerned, however, that passing
null as env results in clearing the child environment. These concerns are
simply that the most common desire is to inherit the environment, and that
there is no parameter that simply says "inherit parent environment," you
have to call a different function.
I suppose it's no different than exec, which you have to call the right
function depending on what you want.
So this sounds fine. The toEnvz still should be fixed to add an extra
null, I'm assuming you're doing that right? :)
I think the bug stems from the fact that, at some intermediate stage of
the development, pipeProcessImpl() used to call spawnProcessImpl()
directly. I later changed this to spawnProcess(), but forgot to remove
the null parameter. I'll simply remove it, and everything will work as
intended.
OK, this makes sense.
Initially, I wrote spawnProcess() the way you suggest, i.e. that a
passing a null AA is equivalent to omitting it. But then we are left
with no simple way to explicitly clear the child's environment. We
could make a distinction between a "null" and an "empty" AA, but making
a non-null empty AA is a hassle. I think it is better the way it is now.
OK
I don't think we need to support clearing the child's environment in
pipeProcess(). I suspect it is a rare need, and the user will just have
to deal with spawnProcess() directly in that case. (It's like how there
are all kinds of different exec*() functions in C, but only one, simple,
popen() function.)
Agree.
-Steve
