tests/coro-gc: create test for boehm stack patch

Regression test for NixOS#7679

src/libexpr/tests/coro-gc.cc

@@ -0,0 +1,99 @@
+#include <gtest/gtest.h>
+#if HAVE_BOEHMGC
+#include <gc/gc.h>
+#endif
+
+#include "eval.hh"
+#include "serialise.hh"
+
+
+#define guard_gc(x) GC_register_finalizer((void*)x, finalizer, x##_collected, nullptr, nullptr)
+
+
+namespace nix {
+#if HAVE_BOEHMGC
+    static bool* uncollectable_bool() {
+        bool* res = (bool*)GC_MALLOC_UNCOLLECTABLE(1);
+        *res = false;
+        return res;
+    }
+
+    static void finalizer(void *obj, void *data) {
+        //printf("finalizer: obj %p data %p\n", obj, data);
+        *((bool*)data) = true;
+    }
+
+    // Generate 2 objects, discard one, run gc,
+    // see if one got collected and the other didn't
+    static void testFinalizerCalls() {
+        bool* do_collect_collected = uncollectable_bool();
+        bool* dont_collect_collected = uncollectable_bool();
+        {
+            volatile void* do_collect = GC_MALLOC_ATOMIC(128);
+            guard_gc(do_collect);
+        }
+        volatile void* dont_collect = GC_MALLOC_ATOMIC(128);
+        guard_gc(dont_collect);
+        GC_gcollect();
+        GC_invoke_finalizers();
+
+        ASSERT_TRUE(*do_collect_collected);
+        ASSERT_FALSE(*dont_collect_collected);
+        ASSERT_NE(nullptr, dont_collect);
+    }
+
+    // This test tests that boehm handles coroutine stacks correctly
+    TEST(CoroGC, CoroutineStackNotGCd) {
+        initGC();
+        testFinalizerCalls();
+
+        bool* dont_collect_collected = uncollectable_bool();
+        bool* do_collect_collected = uncollectable_bool();
+
+        volatile void* dont_collect = GC_MALLOC_ATOMIC(128);
+        guard_gc(dont_collect);
+        {
+            volatile void* do_collect = GC_MALLOC_ATOMIC(128);
+            guard_gc(do_collect);
+        }
+
+        auto source = sinkToSource([&](Sink& sink) {
+            testFinalizerCalls();
+
+            bool* dont_collect_inner_collected = uncollectable_bool();
+            bool* do_collect_inner_collected = uncollectable_bool();
+
+            volatile void* dont_collect_inner = GC_MALLOC_ATOMIC(128);
+            guard_gc(dont_collect_inner);
+            {
+                volatile void* do_collect_inner = GC_MALLOC_ATOMIC(128);
+                guard_gc(do_collect_inner);
+            }
+            // pass control to main
+            writeString("foo", sink);
+
+            ASSERT_TRUE(*do_collect_inner_collected);
+            ASSERT_FALSE(*dont_collect_inner_collected);
+            ASSERT_NE(nullptr, dont_collect_inner);
+
+            // pass control to main
+            writeString("bar", sink);
+        });
+
+        // pass control to coroutine
+        std::string foo = readString(*source);
+        ASSERT_EQ(foo, "foo");
+
+        GC_gcollect();
+        GC_invoke_finalizers();
+
+        // pass control to coroutine
+        std::string bar = readString(*source);
+        ASSERT_EQ(bar, "bar");
+
+        ASSERT_FALSE(*dont_collect_collected);
+        ASSERT_TRUE(*do_collect_collected);
+        ASSERT_NE(nullptr, dont_collect);
+    }
+#endif
+}

src/libexpr/tests/local.mk

@@ -16,4 +16,4 @@ libexpr-tests_CXXFLAGS += -I src/libexpr -I src/libutil -I src/libstore -I src/l
 
 libexpr-tests_LIBS = libstore-tests libutils-tests libexpr libutil libstore libfetchers
 
-libexpr-tests_LDFLAGS := $(GTEST_LIBS) -lgmock
+libexpr-tests_LDFLAGS := $(GTEST_LIBS) -lgmock -lboost_context