diff options
Diffstat (limited to 'build2/algorithm')
| -rw-r--r-- | build2/algorithm | 31 |
1 files changed, 16 insertions, 15 deletions
diff --git a/build2/algorithm b/build2/algorithm index da38f19..601d2ef 100644 --- a/build2/algorithm +++ b/build2/algorithm @@ -300,46 +300,47 @@ namespace build2 // which ones should be used for timestamp comparison. If the filter is // NULL, then all the prerequisites are used. // - // Note that the return value is a pair with the second half indicating - // whether any prerequisites were updated. This is used to handle the - // situation where some prerequisites were updated but no update of the - // target is necessary. In this case we still signal that the target was - // (conceptually, but not physically) changed. This is important both to - // propagate the fact that some work has been done and to also allow our - // dependents to detect this case if they are up to something tricky (like - // recursively linking liba{} prerequisites). + // Note that the return value is an optional target state. If the target + // needs updating, then the value absent. Otherwise it is the state that + // should be returned. This is used to handle the situation where some + // prerequisites were updated but no update of the target is necessary. In + // this case we still signal that the target was (conceptually, but not + // physically) changed. This is important both to propagate the fact that + // some work has been done and to also allow our dependents to detect this + // case if they are up to something tricky (like recursively linking liba{} + // prerequisites). // // Note that because we use mtime, this function should normally only be // used in the perform_update action (which is straight). // using prerequisite_filter = function<bool (const target&)>; - pair<bool, target_state> + optional<target_state> execute_prerequisites (action, const target&, const timestamp&, const prerequisite_filter& = nullptr); // Another version of the above that does two extra things for the caller: // it determines whether the action needs to be executed on the target based - // on the passed timestamp and, if so, finds a prerequisite of the specified - // type (e.g., a source file). If there are multiple prerequisites of this - // type, then the first is returned (this can become important if additional + // on the passed timestamp and finds a prerequisite of the specified type + // (e.g., a source file). If there are multiple prerequisites of this type, + // then the first is returned (this can become important if additional // prerequisites of the same type may get injected). // template <typename T> - pair<const T*, target_state> + pair<optional<target_state>, const T&> execute_prerequisites (action, const target&, const timestamp&, const prerequisite_filter& = nullptr); - pair<const target*, target_state> + pair<optional<target_state>, const target&> execute_prerequisites (const target_type&, action, const target&, const timestamp&, const prerequisite_filter& = nullptr); template <typename T> - pair<const T*, target_state> + pair<optional<target_state>, const T&> execute_prerequisites (const target_type&, action, const target&, const timestamp&, |