diff options
Diffstat (limited to 'build2/variable')
| -rw-r--r-- | build2/variable | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/build2/variable b/build2/variable index 6c579dd..35530ca 100644 --- a/build2/variable +++ b/build2/variable @@ -1219,11 +1219,7 @@ namespace build2 lookup find (const target_type&, const string& tname, const variable&) const; - // In many places we assume that we can store a reference to the returned - // variable value (e.g., install::lookup_install()). As a result, in case - // of append/prepend where we calculate the value dynamically, we have to - // cache it (note, however, that if the value becomes stale, there is no - // guarantee the references remain valid). + // // The key is the combination of the "original value identity" (as a // pointer to the value in one of the variable_pattern_map's) and the @@ -1241,17 +1237,47 @@ namespace build2 map_type map_; }; - // Variable override cache. + // Value caching. Used for overrides as well as target type/pattern-specific + // append/prepend. + // + // In many places we assume that we can store a reference to the returned + // variable value (e.g., install::lookup_install()). As a result, in these + // cases where we calculate the value dynamically, we have to cache it + // (note, however, that if the value becomes stale, there is no guarantee + // the references remain valid). // - struct variable_override_value + template <typename K> + class variable_cache { - variable_map::value_data value; - const variable_map* stem_vars = nullptr; // NULL means there is no stem. + public: + // If the returned unique lock is locked, then the value has been + // invalidated. + // + pair<value&, ulock> + insert (K, const lookup& stem); + + private: + struct entry_type + { + build2::value value; + + // Location of the stem as well as the version on which this cache + // value is based. Used to track the location and value of the stem + // for cache invalidation. NULL/0 means there is no stem. + // + const variable_map* stem_vars = nullptr; + size_t stem_version = 0; + }; + + using map_type = std::map<K, entry_type>; + + map_type m_; }; - using variable_override_cache = std::map<pair<const variable_map*, - const variable*>, - variable_override_value>; + // Allocated in main(). + // + extern size_t variable_cache_mutex_shard_size; + extern unique_ptr<shared_mutex[]> variable_cache_mutex_shard; } #include <build2/variable.ixx> |