diff options
Diffstat (limited to 'libbuild2/context.hxx')
| -rw-r--r-- | libbuild2/context.hxx | 90 |
1 files changed, 47 insertions, 43 deletions
diff --git a/libbuild2/context.hxx b/libbuild2/context.hxx index b426ea0..1d46309 100644 --- a/libbuild2/context.hxx +++ b/libbuild2/context.hxx @@ -160,6 +160,53 @@ namespace build2 // class LIBBUILD2_SYMEXPORT context { + public: + // In order to perform each operation the build system goes through the + // following phases: + // + // load - load the buildfiles + // match - search prerequisites and match rules + // execute - execute the matched rule + // + // The build system starts with a "serial load" phase and then continues + // with parallel match and execute. Match, however, can be interrupted + // both with load and execute. + // + // Match can be interrupted with "exclusive load" in order to load + // additional buildfiles. Similarly, it can be interrupted with (parallel) + // execute in order to build targetd required to complete the match (for + // example, generated source code or source code generators themselves). + // + // Such interruptions are performed by phase change that is protected by + // phase_mutex (which is also used to synchronize the state changes + // between phases). + // + // Serial load can perform arbitrary changes to the build state. Exclusive + // load, however, can only perform "island appends". That is, it can + // create new "nodes" (variables, scopes, etc) but not (semantically) + // change already existing nodes or invalidate any references to such (the + // idea here is that one should be able to load additional buildfiles as + // long as they don't interfere with the existing build state). The + // "islands" are identified by the load_generation number (1 for the + // initial/serial load). It is incremented in case of a phase switch and + // can be stored in various "nodes" to verify modifications are only done + // "within the islands". Another example of invalidation would be + // insertion of a new scope "under" an existing target thus changing its + // scope hierarchy (and potentially even its base scope). This would be + // bad because we may have made decisions based on the original hierarchy, + // for example, we may have queried a variable which in the new hierarchy + // would "see" a new value from the newly inserted scope. + // + // The special load_generation value 0 indicates initialization before + // anything has been loaded. Currently, it is changed to 1 at the end + // of the context constructor. + // + // Note must come (and thus initialized) before the data_ member. + // + run_phase phase = run_phase::load; + size_t load_generation = 0; + + private: struct data; unique_ptr<data> data_; @@ -227,49 +274,6 @@ namespace build2 const vector<name>* trace_match = nullptr; const vector<name>* trace_execute = nullptr; - // In order to perform each operation the build system goes through the - // following phases: - // - // load - load the buildfiles - // match - search prerequisites and match rules - // execute - execute the matched rule - // - // The build system starts with a "serial load" phase and then continues - // with parallel match and execute. Match, however, can be interrupted - // both with load and execute. - // - // Match can be interrupted with "exclusive load" in order to load - // additional buildfiles. Similarly, it can be interrupted with (parallel) - // execute in order to build targetd required to complete the match (for - // example, generated source code or source code generators themselves). - // - // Such interruptions are performed by phase change that is protected by - // phase_mutex (which is also used to synchronize the state changes - // between phases). - // - // Serial load can perform arbitrary changes to the build state. Exclusive - // load, however, can only perform "island appends". That is, it can - // create new "nodes" (variables, scopes, etc) but not (semantically) - // change already existing nodes or invalidate any references to such (the - // idea here is that one should be able to load additional buildfiles as - // long as they don't interfere with the existing build state). The - // "islands" are identified by the load_generation number (1 for the - // initial/serial load). It is incremented in case of a phase switch and - // can be stored in various "nodes" to verify modifications are only done - // "within the islands". Another example of invalidation would be - // insertion of a new scope "under" an existing target thus changing its - // scope hierarchy (and potentially even its base scope). This would be - // bad because we may have made decisions based on the original hierarchy, - // for example, we may have queried a variable which in the new hierarchy - // would "see" a new value from the newly inserted scope. - // - // The special load_generation value 0 indicates initialization before - // anything has been loaded. Currently, it is changed to 1 at the end - // of the context constructor. - // - run_phase phase = run_phase::load; - size_t load_generation = 0; - // A "tri-mutex" that keeps all the threads in one of the three phases. // When a thread wants to switch a phase, it has to wait for all the other // threads to do the same (or release their phase locks). The load phase |