From fe7e924026cb2798afd4b7dfee4be1bdbd6fc066 Mon Sep 17 00:00:00 2001 From: eldritch horrors Date: Thu, 21 Mar 2024 21:27:07 +0100 Subject: [PATCH] libutil: drop Pool resources on exceptional free if a scope owning a resource does not gracefully drop that resource while handling exceptions from deeper down the call stack we should assume the resource is invalid state and drop it. currently it *is* true that such cases do not cause resources to be freed, but thanks to validator misuses this has so far not caused any larger problem. Change-Id: Ie4f91bcd60a64d05c5ff9d22cc97954816d13b97 --- src/libutil/pool.hh | 9 ++++++++- tests/unit/libutil/pool.cc | 15 +++++++++++++++ 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/src/libutil/pool.hh b/src/libutil/pool.hh index 6247b6125..548e7ce69 100644 --- a/src/libutil/pool.hh +++ b/src/libutil/pool.hh @@ -1,6 +1,7 @@ #pragma once ///@file +#include #include #include #include @@ -118,7 +119,7 @@ public: if (!r) return; { auto state_(pool.state.lock()); - if (!bad) + if (!bad && !std::uncaught_exceptions()) state_->idle.push_back(ref(r)); assert(state_->inUse); state_->inUse--; @@ -134,6 +135,12 @@ public: Handle get() { + // we do not want to handle the complexity that comes with allocating + // resources during stack unwinding. it would be possible to do this, + // but doing so requires more per-handle bookkeeping to properly free + // resources allocated during unwinding. that effort is not worth it. + assert(std::uncaught_exceptions() == 0); + { auto state_(state.lock()); diff --git a/tests/unit/libutil/pool.cc b/tests/unit/libutil/pool.cc index 127e42dda..a3743e601 100644 --- a/tests/unit/libutil/pool.cc +++ b/tests/unit/libutil/pool.cc @@ -124,4 +124,19 @@ namespace nix { ASSERT_NE(h->num, counter); } } + + TEST(Pool, throwingOperationDropsResource) + { + auto createResource = []() { return make_ref(); }; + + Pool pool = Pool((size_t)1, createResource); + + ASSERT_THROW({ + auto _r = pool.get(); + ASSERT_EQ(pool.count(), 1); + throw 1; + }, int); + + ASSERT_EQ(pool.count(), 0); + } }