resolver: replace init's cleanup lambda with a member; lcov --list ignores inconsistent

gcov 15 marks the lambda as not hit while its lines are, which lcov 2
rejects.

Co-Authored-By: Claude <noreply@anthropic.com>

CMakeLists.txt

@@ -139,6 +139,7 @@ if (ENABLE_COVERAGE)
                         --include ${PROJECT_SOURCE_DIR}/src/*
                         --ignore-errors mismatch,unused,empty,gcov,inconsistent
                 COMMAND ${LCOV_EXECUTABLE} --list ${PROJECT_BINARY_DIR}/coverage.info
+                        --ignore-errors inconsistent
                 COMMAND ${GENHTML_EXECUTABLE} ${PROJECT_BINARY_DIR}/coverage.info
                         --ignore-errors inconsistent
                         --output-directory ${PROJECT_BINARY_DIR}/coverage-html

src/relay/resolver.cpp

@@ -40,14 +40,9 @@ Status Resolver::init(event::Loop &loop, const char *nameservers, bool ipv6_firs
         ares_library_cleanup();
         return fail(Errc::config);
     }
-    auto abandon = [this] {
-        ares_destroy(channel_);
-        channel_ = nullptr;
-        ares_library_cleanup();
-    };
     if (nameservers != nullptr && ares_set_servers_ports_csv(channel_, nameservers) != ARES_SUCCESS) {
         LOGE("failed to set nameservers %s", nameservers);
-        abandon();
+        abandon_channel();
         return fail(Errc::config);
     }
     loop_       = &loop;
@@ -56,12 +51,20 @@ Status Resolver::init(event::Loop &loop, const char *nameservers, bool ipv6_firs
         w.owner = this;
     }
     if (Status opened = timer_.open(loop, *this); !opened) {
-        abandon();
+        abandon_channel();
         return opened;
     }
     return {};
 }
 
+// Undo init() after the channel was created.
+void Resolver::abandon_channel() noexcept
+{
+    ares_destroy(channel_);
+    channel_ = nullptr;
+    ares_library_cleanup();
+}
+
 Status Resolver::resolve(const char *host, std::uint16_t port, const ResolveCallback &cb) noexcept
 {
     if (channel_ == nullptr) {

src/relay/resolver.hpp

@@ -82,6 +82,7 @@ private:
     static void sock_state(void *data, ares_socket_t s, int readable, int writable) noexcept;
     static void on_host(void *arg, int status, int timeouts, hostent *he) noexcept;
     void on_timer() noexcept;
+    void abandon_channel() noexcept;
     void rearm() noexcept;
     void finish(Query *q, int status) noexcept;
     void on_closed_all() noexcept;