Stop using dbcancel as the nogvl unblock function

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## (unreleased)
 
+* Do not use `dbcancel` as the `rb_thread_call_without_gvl` unblock function. An interrupt (for example SIGCHLD) during `dbsqlok`/`dbresults`/`dbnextrow` aborted the batch and returned empty results. Client `:timeout` is unchanged.
+
 ## 3.4.0
 
 * Add Ruby 4.0 to the cross compile list

ext/tiny_tds/result.c

@@ -89,19 +89,17 @@ VALUE rb_tinytds_new_result_obj(tinytds_client_wrapper *cwrap)
 
 // No GVL Helpers
 
+/* Do not pass dbcancel as the unblock function. MRI invokes the UBF
+   whenever the waiting thread has a pending interrupt, including
+   process-directed signals such as SIGCHLD delivered to main.
+   dbcancel then aborts the SQL batch and Result#each treats FAIL as
+   an empty success. Client :timeout still uses dbsetinterrupt. */
 #define NOGVL_DBCALL(_dbfunction, _client) ( \
   (RETCODE)(intptr_t)rb_thread_call_without_gvl( \
     (void *(*)(void *))_dbfunction, _client, \
-    (rb_unblock_function_t*)dbcancel_ubf, _client ) \
+    NULL, NULL ) \
 )
 
-static void dbcancel_ubf(DBPROCESS *client)
-{
-  GET_CLIENT_USERDATA(client);
-  dbcancel(client);
-  userdata->dbcancel_sent = 1;
-}
-
 static void nogvl_setup(DBPROCESS *client)
 {
   GET_CLIENT_USERDATA(client);

test/client_test.rb

@@ -1,4 +1,5 @@
 require "test_helper"
+require "rbconfig"
 
 class ClientTest < TinyTds::TestCase
   describe "with valid credentials" do
@@ -95,6 +96,23 @@ class ClientTest < TinyTds::TestCase
       assert_new_connections_work
     end
 
+    it "does not cancel a query when another thread reaps a child process" do
+      skip if sqlserver_azure?
+      client = new_connection timeout: 15
+      reaper = Thread.new do
+        sleep 0.5
+        5.times do
+          Process.wait(Process.spawn(RbConfig.ruby, "-e", "nil"))
+          sleep 0.2
+        end
+      end
+      rows = client.execute("WaitFor Delay '00:00:02'; SELECT 42 AS [n]").each
+      reaper.join
+      assert_equal 1, rows.length
+      assert_equal 42, rows.first["n"]
+      close_client(client)
+    end
+
     it "raises TinyTds exception with long query past :timeout option" do
       client = new_connection timeout: 1
       action = lambda { client.execute("WaitFor Delay '00:00:02'").do }