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-rw-r--r--libbuild2/rule.cxx72
1 files changed, 56 insertions, 16 deletions
diff --git a/libbuild2/rule.cxx b/libbuild2/rule.cxx
index 2e5fe5d..5f532ef 100644
--- a/libbuild2/rule.cxx
+++ b/libbuild2/rule.cxx
@@ -440,16 +440,6 @@ namespace build2
if (t.data<bool> ())
return &perform_clean_depdb;
- // For update inject dependency on the tool target(s).
- //
- // @@ We could see that it's a target and do it but not sure if we should
- // bother. We dropped this idea of implicit targets in tests. Maybe we
- // should verify path assigned, like we do there? I think we will have
- // to.
- //
- // if (a == perform_update_id)
- // inject (a, t, tgt);
-
if (a == perform_update_id && t.is_a<file> ())
{
return [this] (action a, const target& t)
@@ -476,6 +466,59 @@ namespace build2
const file& t (xt.as<file> ());
const path& tp (t.path ());
+ // The script can reference a program in one of four ways:
+ //
+ // 1. As an (imported) target (e.g., $cli)
+ //
+ // 2. As a process_path_ex (e.g., $cxx.path).
+ //
+ // 3. As a builtin (e.g., sed)
+ //
+ // 4. As a program path/name.
+ //
+ // When it comes to change tracking, there is nothing we can do for (4)
+ // and there is nothing to do for (3) (assuming builtin semantics is
+ // stable/backwards-compatible). The (2) case is handled automatically by
+ // hashing all the variable values referenced by the script (see below),
+ // which in case of process_path_ex includes the checksum, if available.
+ //
+ // This leaves the (1) case, which itself splits into two sub-cases: the
+ // target comes with the dependency information (e.g., imported from a
+ // project via an export stub) or it does not (e.g., imported as
+ // installed). We don't need to do anything extra for the first sub-case
+ // since the target's state/mtime can be relied upon like any other
+ // prerequisite. Which cannot be said about the second sub-case, where we
+ // reply on checksum that may be included as part of the target metadata.
+ //
+ // So what we are going to do here is hash checksum metadata of every
+ // executable prerequisite target that has it. We do it before executing
+ // in order to include ad hoc prerequisites (which feels like the right
+ // thing to do; the user may mark tools as ad hoc in order to omit them
+ // from $<).
+ //
+ sha256 prog_cs;
+ for (const target* pt: t.prerequisite_targets[a])
+ {
+ if (pt != nullptr)
+ {
+ if (auto* e = pt->is_a<exe> ())
+ {
+ if (auto* ns = cast_null<names> (e->vars[ctx.var_export_metadata]))
+ {
+ // Metadata variable prefix is in the second name.
+ //
+ assert (ns->size () == 2 && (*ns)[1].simple ());
+
+ if (auto* c = cast_null<string> (
+ e->vars[(*ns)[1].value + ".checksum"]))
+ {
+ prog_cs.append (*c);
+ }
+ }
+ }
+ }
+ }
+
// Update prerequisites and determine if any of them render this target
// out-of-date.
//
@@ -593,13 +636,10 @@ namespace build2
l4 ([&]{trace << "prerequisite set change forcing update of " << t;});
}
- // Then the tools checksums.
- //
- // @@ TODO: obtain checksums of all the targets used as commands in
- // the script.
+ // Finally the programs checksum.
//
- //if (dd.expect (csum) != nullptr)
- // l4 ([&]{trace << "compiler mismatch forcing update of " << t;});
+ if (dd.expect (prog_cs.string ()) != nullptr)
+ l4 ([&]{trace << "program checksum change forcing update of " << t;});
}
// Update if depdb mismatch.