Add build.version.interface

This build system interface version should be embedded into build system
modules as load_suffix.

1 files changed, 11 insertions, 0 deletions

diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx
index 815a556..e7f9751 100644
--- a/libbuild2/context.cxx
+++ b/libbuild2/context.cxx
@@ -432,6 +432,9 @@ namespace build2
         gs.assign (variable_pool::instance.insert<T> (var)) = move (val);
       };
 
+      // Note: here we assume epoch will always be 1 and therefore omit the
+      //       project_ prefix in a few places.
+      //
       set ("build.version", v.string_project ());
 
       set ("build.version.number", v.version);
@@ -455,6 +458,14 @@ namespace build2
       set ("build.version.snapshot_id",     v.snapshot_id); // string
       set ("build.version.snapshot_string", v.string_snapshot ());
 
+      // Build system interface version. In particular, it is embedded into
+      // build system modules as load_suffix.
+      //
+      set ("build.version.interface",
+           v.pre_release ()
+           ? v.string_project_id ()
+           : to_string (v.major ()) + '.' + to_string (v.minor ()));
+
       // Allow detection (for example, in tests) whether this is a staged
       // toolchain.
       //