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未定义的行为问题 (UBSan)

目标和动力

C/C++ 代码在运行时可能会存在未定义的行为。导致未定义的行为包括：

使用未对齐指针或 null 指针。
有符号整数溢出。
转换为会溢出的浮点类型，或者从浮点类型之间进行转换目标位置

为了大规模发现这些问题，我们推出了对紫红色的未定义行为排错程序 (UBSan)。此运行时检查原为默认启用。尽管发现的大多数问题都已修正，并且新问题不会引入源代码树后，还有待解决的 UBSan 问题。

技术背景

需精通 C/C++ 编程。

如何提供帮助

选择任务

查看待解决的 UBSan 问题，然后选择要修正的错误。

或者，查找具有抑制的构建目标：

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" ]
}

您可以专注于您拥有的代码，也可以在整个树中随机选择目标。

执行任务

第一步是解除禁止状态并解决问题。UBSan 通过记录根本原因和堆栈轨迹来提供问题排查信息问题发生的时间。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>

如果是 UBSan 错误，该错误已包含此信息但相关信息可能会公开，具体取决于错误报告的提交时间日期。您也可以尝试重现问题，例如通过运行移除禁用或将更改发送到 CQ 的测试。

如果无法重现问题，并且已解除禁止设置的更改然后继续学习下一部分。如果违反规则的代码已修复或移除，但更改的作者留下了抑制/错误完好无损。

有关 UndefinedBehaviorSanitizer 和可用检查的更多信息可在上游文档中找到。

完成任务

请在更改说明中标记封面 bug，如下所示：

Fixed: xxxxx

通过所有者查找审核者，然后合并您的更改。

示例

赞助商

如有疑问或需要更新状态，欢迎与我们联系：