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authorBoris Kolpackov <boris@codesynthesis.com>2017-04-28 08:33:42 +0200
committerBoris Kolpackov <boris@codesynthesis.com>2017-04-28 08:33:42 +0200
commit593fd960891027b97567b2622ed4b6c16070ab36 (patch)
treef4cb383f8606fde6adff7ac9f90a20cc9ad59840 /build2/algorithm
parentac402e1fef2c13b5860ca5223d764bbfdfb867e3 (diff)
Implement support for pre-processing version headers (or other files)
Also implement the build system version check.
Diffstat (limited to 'build2/algorithm')
-rw-r--r--build2/algorithm31
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&,