[Scons-users] Value nodes and --debug=explain

Fri Oct 30 20:02:15 EDT 2015

Do you know what Issue number that corresponds to? That patch doesn't look
familiar to me.

V/R,
William

On Fri, Oct 30, 2015 at 12:23 PM, Tom Tanner (BLOOMBERG/ LONDON) <
ttanner2 at bloomberg.net> wrote:

> There was a discussion about this earlier. There's a fix sculling around
> for it somewhere. This patch should apply to Node/__init__.py
>
>
>
> @@ -1198,59 +1198,51 @@ class Node(object):
> old_bkids = old.bsources + old.bdepends + old.bimplicit
> old_bkidsigs = old.bsourcesigs + old.bdependsigs + old.bimplicitsigs
> except AttributeError:
> return "Cannot explain why `%s' is being rebuilt: No previous build
> information found\n" % self
>
> new = self.get_binfo()
>
> new_bkids = new.bsources + new.bdepends + new.bimplicit
> new_bkidsigs = new.bsourcesigs + new.bdependsigs + new.bimplicitsigs
>
> + osig = dict(zip(old_bkids, old_bkidsigs))
> +
> # The sources and dependencies we'll want to report are all stored
> # as relative paths to this target's directory, but we want to
> # report them relative to the top-level SConstruct directory,
> # so we only print them after running them through this lambda
> # to turn them into the right relative Node and then return
> # its string.
> def stringify( s, E=self.dir.Entry ) :
> if hasattr( s, 'dir' ) :
> return str(E(s))
> return str(s)
>
> - # We stringify everything because we seem to get different instances of
> - # each Value object even if they have the same value. As this
> - # stringifies everything on output, I don't think we really care -
> - # though if you happen to have a Value object whose value matches a
> - # filename, the resultant output wil be confusing, whichever way you
> - # deal with it.
> - old_kids = list(map(stringify, old_bkids))
> - new_kids = list(map(stringify, new_bkids))
> - osig = dict(zip(old_kids, old_bkidsigs))
> -
> lines = []
>
> - removed = [x for x in old_kids if not x in new_kids]
> + removed = [x for x in old_bkids if not x in new_bkids]
> if removed:
> + removed = list(map(stringify, removed))
> fmt = "`%s' is no longer a dependency\n"
> lines.extend([fmt % s for s in removed])
>
> for k in new_bkids:
> - ks = stringify(k)
> - if not ks in old_kids:
> - lines.append("`%s' is a new dependency\n" % ks)
> - elif k.changed_since_last_build(self, osig[ks]):
> - lines.append("`%s' changed\n" % ks)
> + if not k in old_bkids:
> + lines.append("`%s' is a new dependency\n" % stringify(k))
> + elif k in osig and k.changed_since_last_build(self, osig[k]):
> + lines.append("`%s' changed\n" % stringify(k))
>
> - if len(lines) == 0 and old_kids != new_kids:
> + if len(lines) == 0 and old_bkids != new_bkids:
> lines.append("the dependency order changed:\n" +
> - "%sold: %s\n" % (' ' * 15, old_kids) +
> - "%snew: %s\n" % (' ' * 15, new_kids))
> + "%sold: %s\n" % (' ' * 15, list(map(stringify, old_bkids))) +
> + "%snew: %s\n" % (' ' * 15, list(map(stringify, new_bkids))))
>
> if old.bactsig != new.bactsig:
> def fmt_with_title(title, strlines):
> lines = strlines.split('\n')
> sep = '\n' + ' ' * (15 + len(title))
> return ' ' * 15 + title + sep.join(lines) + '\n'
>
> if old.bact == new.bact:
> lines.append("the contents of the build action changed\n" +
> fmt_with_title('action: ', new.bact))
>
> From: scons-users at scons.org At: Oct 29 2015 20:41:02
> To: scons-users at scons.org
> Subject: Re:[Scons-users] Value nodes and --debug=explain
>
>
> I've noticed that, if I use Value nodes as sources, if one changes, then the
> explain output claims that ALL the Value node sources are completely
>
> different.  That is, for a Value that did not change, it claims it is both no
> longer a dependency, and also a new dependency.  I would think it should
> only emit messages about Values that actually changed.
>
> For the following SConstruct:
>     env = Environment()
>
>     sources = [
>         env.Value('a'),
>         env.Value('b'),
>     ]
>     env.Command('tgt', sources, [
>         'touch $TARGET'
>     ])
>
> If, after building once, I change the 'b' Value to 'c', then I see:
>     $ scons --debug=explain
>     scons: Reading SConscript files ...
>     scons: done reading SConscript files.
>     scons: Building targets ...
>     scons: rebuilding `tgt' because:
>                `a' is no longer a dependency
>                `b' is no longer a dependency
>                `a' is a new dependency
>                `c' is a new dependency
>     touch tgt
>     scons: done building targets.
>
>
> The cause here seems to that, in SCons.Node.explain(), when it checks
> whether a given node from the old_bkids is in new_kids, and vice-versa, the
> check always fails, because env.Value('a') != env.Value('a'), and because
> there's no __hash__ override, the object id is used when doing lookups of
> nodes as keys in osig (a dictionary).
>
> So, if I add the following to SCons.Node.Python.Value:
>     def __eq__(self, other):
>         if isinstance(other, Value):
>             return self.value == other.value
>         return False
>
>     def __hash__(self):
>         return hash(self.value)
>
> Then I get output more inline with what I'd expect:
>     $ scons --debug=explain
>     scons: Reading SConscript files ...
>     scons: done reading SConscript files.
>     scons: Building targets ...
>     scons: rebuilding `tgt' because:
>                `c' is no longer a dependency
>                `d' is a new dependency
>     touch tgt
>     scons: done building targets.
>
> However, I wonder if perhaps I'm missing something obvious that doesn't
> require a code change to SCons?
>
> I've tested both 2.3.2 and 2.4; both have the same behavior.
>
>  - Matt
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>
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