本頁面由 Cloud Translation API 翻譯而成。

未定義的行為問題 (UBSan)

目標和動力

C/C++ 程式碼可能會在執行階段出現未定義的行為。常見原因未定義的行為包括：

使用未對齊或空值指標。
帶正負號的整數溢位。
轉換至會溢位的浮點類型，或轉換點類型之間的轉換目的地。

為大規模找出這些問題，我們導入了 Fuchsia 中的未定義行為清理工具 (UBSan)。這項執行階段檢查之前為已於 2020 年預設啟用 CQ，並將現有的違規行為封鎖。儘管多數問題已修正，但新問題不會這個原始碼中提及的開啟應特別留意的 UBSan 問題。

技術背景

需要熟悉 C/C++ 程式設計。

如何提供協助

選取工作

查看尚未解決的 UBSan 問題，然後選擇要修正的錯誤。

或者，您也可以尋找設有抑制的建構目標：

source_set("foo") {
  ...
  # TODO(https://fxbug.dev/xxxxx): UBSan has found an instance of undefined behavior in this target.
  # Disable UBSan for this target temporarily until it is migrated into CI/CQ.
  configs += [ "//build/config:temporarily_disable_ubsan_do_not_use" ]
}

您可以將重點放在自己的程式碼上，或是在整個樹狀結構中挑選隨機目標。

執行工作

第一步是移除系統隱藏狀態並解決問題。烏布桑會記錄根本原因和堆疊追蹤，提供疑難排解資訊測試期間，問題是在執行階段出現。例如：

[2105.728] 1054084.1055594> ../../src/connectivity/wlan/lib/common/cpp/include/wlan/common/element.h:769:48: runtime error: upcast
[2105.728] 1054084.1055594> of misaligned address 0x245287a88d03 for type 'wlan::SupportedMcsRxMcsHead', which requires 8 byte alignment
[2105.729] 1054084.1055594> 0x245287a88d03: note: pointer points here
[2105.729] 1054084.1055594>  62  fe 01 00 ff 00 00 00 01  00 00 00 00 00 00 00 01  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00
[2105.729] 1054084.1055594>               ^
2020/02/20 21:52:42.559678 WARN: on line 16830: could not find module for 0x22ec07646c96
2020/02/20 21:52:42.559792 WARN: on line 16831: could not find module for 0x22ec076466e9
[2105.734] 1054084.1055594>    #0    0x000022ddedc71a41 in wlan::HtCapabilities::ToDdk() const ../../out/default/../../src/connectivity/wlan/lib/common/cpp/include/wlan/common/element.h:769 <<VMO#1054220=wlantap.so>>+0x1dba41
[2105.734] 1054084.1055594>    #1    0x000022ec07646c96 in <>+0x38c96
[2105.734] 1054084.1055594>    #2    0x000022ec076466e9 in <>+0x386e9
[2105.734] 1054084.1055594>    #3    0x000022ddedc71a41 in wlan::HtCapabilities::ToDdk() const ../../out/default/../../src/connectivity/wlan/lib/common/cpp/include/wlan/common/element.h:769 <<VMO#1054220=wlantap.so>>+0x1dba41
2020/02/20 21:49:12.077658 testrunner attempting to close SSH session due to: failed to run SSH command: Process exited with status 101
2020/02/20 21:49:12.077681 testrunner ERROR: failed to send KILL signal over SSH session: EOF
2020/02/20 21:49:12.077689 testrunner ERROR: failed to close SSH session: EOF
[2105.735] 1054084.1055594> {{2020/02/20 21:49:12.081620 testrunner ERROR: failed to run SSH command: Process exited with status 101
not ok 138 fuchsia-pkg://fuchsia.com/wlan-hw-sim-test#meta/configure_legacy_privacy_off.cmx (4.259382565s)
{bt:4:0x22ddedc6d904}}}
[2105.735] 1054084.1055594>    #5    0x000022ddedc6f173 in wlan::ConvertPhyInfo(wlan_info*, fuchsia::wlan::device::PhyInfo const&) ../../out/default/../../src/connectivity/wlan/testing/wlantap-driver/utils.cc:167 <<VMO#1054220=wlantap.so>>+0x1d9173
[2105.735] 1054084.1055594>    #6    0x000022ddedc9521a in wlan::(anonymous namespace)::WlantapPhy::Query(wlanphy_impl_info*) ../../out/default/../../src/connectivity/wlan/testing/wlantap-driver/wlantap-phy.cc:186 <<VMO#1054220=wlantap.so>>+0x1ff21a
[2105.735] 1054084.1055594>    #7    0x000022ddedc94f90 in wlan::$_0::operator()(void*, wlanphy_impl_info*) const ../../out/default/../../src/connectivity/wlan/testing/wlantap-driver/wlantap-phy.cc:410 <<VMO#1054220=wlantap.so>>+0x1fef90
[2105.735] 1054084.1055594>    #8    0x000022ddedc94e8c in wlan::$_0::__invoke(void*, wlanphy_impl_info*) ../../out/default/../../src/connectivity/wlan/testing/wlantap-driver/wlantap-phy.cc:409 <<VMO#1054220=wlantap.so>>+0x1fee8c
[2105.735] 1054084.1055594>    #9    0x000021a1e2e3d3e4 in wlanphy::Device::Query(fit::function_impl<16ul, false, void (fuchsia::wlan::device::QueryResponse)>) ../../out/default/../../src/connectivity/wlan/drivers/wlanphy/device.cc:260 <<VMO#1055531=wlanphy.so>>+0x1ab3e4
[2105.735] 1054084.1055594>    #10   0x000021a1e2e9e77e in fuchsia::wlan::device::Phy_Stub::Dispatch_(fidl::Message, fidl::internal::PendingResponse) ../../out/default/fidling/gen/sdk/fidl/fuchsia.wlan.device/fuchsia/wlan/device/cpp/fidl.cc:739 <<VMO#1055531=wlanphy.so>>+0x20c77e
[2105.735] 1054084.1055594>    #11   0x000021a1e2fa9a26 in fidl::internal::StubController::OnMessage(fidl::Message) ../../out/default/../../sdk/lib/fidl/cpp/internal/stub_controller.cc:30 <<VMO#1055531=wlanphy.so>>+0x317a26
[2105.735] 1054084.1055594>    #12   0x000021a1e2f916b4 in fidl::internal::MessageReader::ReadAndDispatchMessage(fidl::MessageBuffer*) ../../out/default/../../sdk/lib/fidl/cpp/internal/message_reader.cc:235 <<VMO#1055531=wlanphy.so>>+0x2ff6b4
[2105.735] 1054084.1055594>    #13   0x000021a1e2f91bde in fidl::internal::MessageReader::OnHandleReady(async_dispatcher*, int, zx_packet_signal const*) ../../out/default/../../sdk/lib/fidl/cpp/internal/message_reader.cc:179 <<VMO#1055531=wlanphy.so>>+0x2ffbde
[2105.735] 1054084.1055594>    #14   0x000021a1e2f8f13c in fidl::internal::MessageReader::CallHandler(async_dispatcher*, async_wait*, int, zx_packet_signal const*) ../../out/default/../../sdk/lib/fidl/cpp/internal/message_reader.cc:166 <<VMO#1055531=wlanphy.so>>+0x2fd13c
[2105.735] 1054084.1055594>    #15.1 0x000021a1e3273e31 in async_loop_run_once ../../out/default/../../sdk/lib/async-loop/loop.c:0 <<VMO#1055531=wlanphy.so>>+0x5e1e31
[2105.735] 1054084.1055594>    #15   0x000021a1e3273e31 in async_loop_run ../../out/default/../../sdk/lib/async-loop/loop.c:253 <<VMO#1055531=wlanphy.so>>+0x5e1e31
[2105.735] 1054084.1055594>    #16   0x000021a1e3275b76 in async_loop_run_thread ../../out/default/../../sdk/lib/async-loop/loop.c:799 <<VMO#1055531=wlanphy.so>>+0x5e3b76
[2105.736] 1054084.1055594>    #17   0x000041f10d1f067e in start_c11 ../../out/default.zircon/../../zircon/third_party/ulib/musl/pthread/pthread_create.c:37 <libc.so>+0xaa67e
[2105.736] 1054084.1055594>    #18   0x000041f10d3017ad in thread_trampoline ../../out/default.zircon/../../zircon/system/ulib/runtime/thread.c:93 <libc.so>+0x1bb7ad
[2105.736] 1054084.1055594>

如果您正在接收 UBSan 錯誤，則錯誤所對應的錯誤即為但這取決於錯誤提交時間。您也可以嘗試重現問題，例如執行移除抑制值的測試，或將變更傳送至 CQ。

如果無法重現問題，且已移除禁播設定的變更通過 CQ，然後繼續進行下一部分。這可能是因為程式碼已修正或移除，但變更的作者留下隱藏/錯誤分享各種資訊

關於 UndefinedBehaviorSanitizer 和可用檢查的其他資訊請參閱上游文件。

完成工作

在變更說明中標記封面錯誤，如下所示：

Fixed: xxxxx

透過擁有者尋找審查人員並合併變更。

範例

贊助者

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