Ensure that Callback is called only once

Also, make Callback movable but uncopyable.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 3bb9db0b723b..88a5b2f448bd 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -365,8 +365,10 @@ void Store::queryPathInfo(const Path & storePath,
 
     } catch (...) { return callback.rethrow(); }
 
+    auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
+
     queryPathInfoUncached(storePath,
-        {[this, storePath, hashPart, callback](std::future<std::shared_ptr<ValidPathInfo>> fut) {
+        {[this, storePath, hashPart, callbackPtr](std::future<std::shared_ptr<ValidPathInfo>> fut) {
 
             try {
                 auto info = fut.get();
@@ -386,8 +388,8 @@ void Store::queryPathInfo(const Path & storePath,
                     throw InvalidPath("path '%s' is not valid", storePath);
                 }
 
-                callback(ref<ValidPathInfo>(info));
-            } catch (...) { callback.rethrow(); }
+                (*callbackPtr)(ref<ValidPathInfo>(info));
+            } catch (...) { callbackPtr->rethrow(); }
         }});
 }