AndroidT(13) Log 系统 -- C plus plus 语言格式的LOG输出(二)

flagstaffChen

已于 2022-12-10 13:41:41 修改

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分类专栏： Android System & Framework 文章标签： c语言 android logd log system logcat

于 2022-11-28 21:06:10 首次发布

本文链接：https://blog.youkuaiyun.com/u014787262/article/details/128087341

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1.概览

上一章提到的是在Android系统中，以C语言格式方式进行log输出。本章就来讲讲c++语言格式的。

std::cout<<"This is a c++ log"<<std::endl;

在Android中也同样提供了类似的接口

LOG(INFO)<<"This is a c++ log from Android.";

不同的是不需要后加 std::endl 来告知一行结束。在Android的log系统中，天然的就认为一个LOG就对应一行内容。

2. 打印LOG内容所属的类型

2.1 输出 Android系统的LOG到logd

在 Android 中，有着非常多的子系统，所以 Android 的 LOG 系统是支持多个buffer的，即不同类型的log写入不同的buffer中。它所支持的log类型可以简单的使用对应版本的 logcat 工具查看

board:/ # logcat -h
Usage: logcat [options] [filterspecs]

General options:
  -b, --buffer=<buffer>       Request alternate ring buffer(s):
                                main system radio events crash default all
                              Additionally, 'kernel' for userdebug and eng builds, and
                              'security' for Device Owner installations.
                              Multiple -b parameters or comma separated list of buffers are
                              allowed. Buffers are interleaved.
                              Default -b main,system,crash,kernel.

在c++语言风格的log接口中是没办法选择buffer输出的，它们默认被输出到 main buffer中去。

2.2 打印内容所属的级别

手头需要做的事有轻重缓急，log中的信息所代表的事项也同样如此。下面是Android log 系统的几个级别

//system\libbase\include\android-base\logging.h
namespace android {
namespace base {
...
enum LogSeverity {
  VERBOSE,
  DEBUG,
  INFO,
  WARNING,
  ERROR,
  FATAL_WITHOUT_ABORT,  // For loggability tests, this is considered identical to FATAL.
  FATAL,
...
};
}
};

前面也说了，c++风格的LOG接口只支持打印到main buffer，所以和上面的log级别组合也就如下几种

//system\libbase\include\android-base\logging.h
#define LOG(severity) LOGGING_PREAMBLE(severity) && LOG_STREAM(severity)

LOG(VERBOSE)
LOG(DEBUG)
LOG(INFO)
LOG(WARNING)
LOG(ERROR)
LOG(FATAL_WITHOUT_ABORT)
LOG(FATAL)

不同级别的log使用场景可以参考上一章节。

2.3 输出 Android系统的LOG到 kmsg

上面我们所说的 main/system/radio buffer实际上都是来自于logd的内部缓存，即属于logd这个进程。
但输出log到kernel中，则需要使用到kmsg了。kmsg大家应该更加的熟悉，因为linux存在时间可比Android悠久的多，它属于linux kernel的log子系统，Android系统是基于linux，所以除了Android系统本身规划的这些log外。还有一套linux kernel的log系统，它暴露的设备节点如下

board:/ # ls /dev/kmsg -Z
u:object_r:kmsg_device:s0 /dev/kmsg

2.4 切换LOG输出 – SetLogger

Android还是一如既往的周到，提供了切换接口

//file:system\libbase\include\android-base\logging.h
LogFunction SetLogger(LogFunction&& logger);

切换kernel log

SetLogger(android::base::KernelLogger);

其中KernelLogger定义如下

// Log to the kernel log (dmesg).
void KernelLogger(LogId log_buffer_id, LogSeverity severity, const char* tag, const char* file, unsigned int line, const char* message);

在代码中，调用了如上接口后，在其之后的log都会被打印到/dev/kmsg中。我们可以通过dmesg来获取。
同样的，我们也可以将log定向到标准输出中

SetLogger(android::base::StdioLogger);

3.使用实例 – logPrintCppStyle

3.1 编译配置 – Android.bp

cc_binary {
    name: "logPrintCppStyle",
    srcs: [
        "*.cpp",
    ],
    shared_libs: [
        "libbase",
    ],
    cppflags: [
        "-Wno-unused-parameter",
    ],
}

C语言风格的log打印接口，只使用了库 libbase，所以只要包含它即可。

3.2 测试源码 – logPrintCppStyle.cpp


#define LOG_TAG     "logPrintCppStyle"


#include <stdlib.h>
#include <android-base/logging.h>//from libbase
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(int argc, char* argv[])
{
    /*
        1.print the log to stdio but not logd
            board:/ # logcat -s logPrintCppStyle&
            [1] 4971
            board:/ # logPrintCppStyle
            LOG(INFO):write INFO level to main buffer
    */
    //android::base::InitLogging(nullptr, android::base::StdioLogger);

    /**
     * 2. print the log to kernel log buffer but not logd 
     *      board:/ # logPrintCppStyle
     *      board:/ # --------- beginning of kernel
     *      11-25 18:22:11.924  4975  4975 I logPrintCppStyle: LOG(INFO):write INFO level to main buffer
     *      board:/ # dmesg|grep logPrintCpp
     *      [15331.396227] logPrintCppStyle: LOG(INFO):write INFO level to main buffer
    */
    //android::base::InitLogging(nullptr, android::base::KernelLogger);

    /**
     * 3.default:
     *      board:/ # logPrintCppStyle
     *      --------- beginning of main
     *      11-25 18:26:59.983  4980  4980 I logPrintCppStyle: LOG(INFO):write INFO level to main buffer
    */
    /**
     * 4.Control the log to be shown by its level
     *      4.1 INFO is the default level. So VERBOSE don't shows in default.
     *      board:/ # logPrintCppStyle
     *          11-24 19:07:43.577  2894  2894 I logPrintCppStyle: LOG(INFO):write log
     *          11-24 19:07:43.578  2894  2894 W logPrintCppStyle: LOG(WARNING):write log
     *          11-24 19:07:43.578  2894  2894 E logPrintCppStyle: LOG(ERROR):write log
     *          11-24 19:07:43.578  2894  2894 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
     *
     *      board:/ # setprop log.tag.logPrintCppStyle V
     *      board:/ # logPrintCppStyle
     *      11-24 19:08:12.676  2925  2925 V logPrintCppStyle: LOG(VERBOSE):write log
     *      11-24 19:08:12.677  2925  2925 D logPrintCppStyle: LOG(DEBUG):write log
     *      11-24 19:08:12.677  2925  2925 I logPrintCppStyle: LOG(INFO):write log
     *      11-24 19:08:12.677  2925  2925 W logPrintCppStyle: LOG(WARNING):write log
     *      11-24 19:08:12.677  2925  2925 E logPrintCppStyle: LOG(ERROR):write log
     *      11-24 19:08:12.677  2925  2925 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
     *
     *      board:/ # setprop log.tag.logPrintCppStyle I
     *      board:/ # logPrintCppStyle
     *      11-24 19:09:17.451  2929  2929 I logPrintCppStyle: LOG(INFO):write log
     *      11-24 19:09:17.451  2929  2929 W logPrintCppStyle: LOG(WARNING):write log
     *      11-24 19:09:17.451  2929  2929 E logPrintCppStyle: LOG(ERROR):write log
     *      11-24 19:09:17.451  2929  2929 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
     *
     *      board:/ # setprop log.tag.logPrintCppStyle E
     *      board:/ # logPrintCppStyle
     *      11-24 19:09:40.640  2931  2931 E logPrintCppStyle: LOG(WARNING):write log
     *      11-24 19:09:40.640  2931  2931 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
     *
     *      board:/ # setprop log.tag.logPrintCppStyle F
     *      board:/ # logPrintCppStyle
     *      11-24 19:09:47.405  2933  2933 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
    */
    LOG(VERBOSE)<<"LOG(VERBOSE):write log";
    LOG(DEBUG)<<"LOG(DEBUG):write log";
    LOG(INFO)<<"LOG(INFO):write log";
    LOG(WARNING)<<"LOG(WARNING):write log";
    LOG(ERROR)<<"LOG(ERROR):write log";
    //LOG(FATAL_WITHOUT_ABORT)<<"LOG(FATAL_WITHOUT_ABORT):write log";
    //LOG(FATAL)<<"LOG(FATAL):write log";

    /**
     * 5. using PLOG to show the detial error when error occurs
     * 11-24 19:17:49.677  2941  2941 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
    */
    open("/dev/fakeDev", O_APPEND);
    PLOG(ERROR) << "PLOG(ERROR):write log";
    /**
     * 6.control the location where log is shown. /dev/dmesg or logd's main buffer
     *   board:/ # logPrintCppStyle
     *   11-24 19:20:31.142  2943  2943 V logPrintCppStyle: LOG(VERBOSE):write log
     *   11-24 19:20:31.143  2943  2943 D logPrintCppStyle: LOG(DEBUG):write log
     *   11-24 19:20:31.143  2943  2943 I logPrintCppStyle: LOG(INFO):write log
     *   11-24 19:20:31.143  2943  2943 W logPrintCppStyle: LOG(WARNING):write log
     *   11-24 19:20:31.143  2943  2943 E logPrintCppStyle: LOG(ERROR):write log
     *   11-24 19:20:31.143  2943  2943 F logPrintCppStyle: LOG(FATAL_WITHOUT_ABORT):write log
     *   11-24 19:20:31.143  2943  2943 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
     *   11-24 19:20:31.143  2943  2943 I logPrintCppStyle: set StdioLogger as Logger...
     *   LOG(INFO):write log
    */
    LOG(INFO)<<"set StdioLogger as Logger...";
    SetLogger(android::base::StdioLogger);
    LOG(INFO)<<"LOG(INFO):write log";
    SetLogger(android::base::KernelLogger);
    /**
     * 7. making the crash in the application
     *  11-24 19:22:38.611  2958  2958 I crash_dump64: performing dump of process 2955 (target tid = 2955)
     *   11-24 19:22:38.642   417   417 I logd    : logdr: UID=0 GID=0 PID=2958 n tail=0 logMask=8 pid=2955 start=0ns deadline=0ns
     *   11-24 19:22:38.648   417   417 I logd    : logdr: UID=0 GID=0 PID=2958 n tail=0 logMask=1 pid=2955 start=0ns deadline=0ns
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : Build fingerprint: 'Fake/full_board_t/board:13/TP1A.220624.014/eng.flagstaff.20220920.145750:userdebug/test-keys'
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : Revision: '0'
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : ABI: 'arm64'
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : Timestamp: 2022-11-24 19:22:38.613264983+0800
     *   11-24 19:22:38.641  2958  2958 F DEBUG   : Process uptime: 2s
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : Cmdline: logPrintCppStyle
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : pid: 2955, tid: 2955, name: logPrintCppStyl  >>> logPrintCppStyle <<<
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : uid: 0
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
     *   11-24 19:22:38.642  2958  2958 F DEBUG   : Abort message: 'LOG(FATAL_WITHOUT_ABORT):write log'
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x0  0000000000000000  x1  0000000000000b8b  x2  0000000000000006  x3  0000007ffea7f850
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x4  000000000000000a  x5  000000000000000a  x6  000000000000000a  x7  7f7f7f7f7f7f7f7f
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x8  00000000000000f0  x9  0000007361352a80  x10 0000000000000001  x11 0000007361393760
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x12 0000007ffea7eb34  x13 0000000000000002  x14 0000000000000000  x15 00000073613568e2
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x16 0000007361400d58  x17 00000073613dc2a0  x18 00000073633e4000  x19 0000000000000b8b
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x20 0000000000000b8b  x21 00000000ffffffff  x22 0000007362f63000  x23 0000000000000000
     *   11-24 19:22:38.642  2958  2958 F DEBUG   :     x24 0000000000000000  x25 0000000000000000  x26 0000000000000000  x27 0000000000000000
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :     x28 0000000000000000  x29 0000007ffea7f8d0
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :     lr  0000007361384248  sp  0000007ffea7f830  pc  0000007361384274  pst 0000000000001000
     *   11-24 19:22:38.643  2958  2958 F DEBUG   : backtrace:
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :       #00 pc 0000000000053274  /apex/com.android.runtime/lib64/bionic/libc.so (abort+164) (BuildId: 2909e25171905ab2aa55000ddb487289)
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :       #01 pc 00000000000063fc  /system/lib64/liblog.so (__android_log_default_aborter+12) (BuildId: ea3eb93b960dede93d1fb67c42ed7273)
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :       #02 pc 0000000000016a50  /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+352) (BuildId: 805c1dfe4ea9454d03b5d1626665b3f0)
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :       #03 pc 00000000000015dc  /system/bin/logPrintCppStyle (main+1404) (BuildId: f7c3609dd3aa7216053ac5cd10d3df82)
     *   11-24 19:22:38.643  2958  2958 F DEBUG   :       #04 pc 000000000004b650  /apex/com.android.runtime/lib64/bionic/libc.so (__libc_init+96) (BuildId: 2909e25171905ab2aa55000ddb487289)
    */
    //LOG(FATAL)<<"LOG(FATAL):write log";

    /**
     * 8.
     *   11-27 12:37:17.677  5706  5706 V logPrintCppStyle: LOG(VERBOSE):write log
     *   11-27 12:37:17.677  5706  5706 D logPrintCppStyle: LOG(DEBUG):write log
     *   11-27 12:37:17.677  5706  5706 I logPrintCppStyle: LOG(INFO):write log
     *   11-27 12:37:17.678  5706  5706 W logPrintCppStyle: LOG(WARNING):write log
     *   11-27 12:37:17.678  5706  5706 E logPrintCppStyle: LOG(ERROR):write log
     *   11-27 12:37:17.678  5706  5706 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
     *   11-27 12:37:17.678  5706  5706 I logPrintCppStyle: set StdioLogger as Logger...
     *   11-27 12:37:17.687  5706  5706 F logPrintCppStyle: Check failed: false == true (false=0, true=1)
     * error information:
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Build fingerprint: 'Fake/full_board_t/board:13/TP1A.220624.014/eng.flagstaff.20220920.145750:userdebug/test-keys'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Revision: '0'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : ABI: 'arm64'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Timestamp: 2022-11-27 12:37:17.707826659+0800
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Process uptime: 1s
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Cmdline: logPrintCppStyle
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : pid: 5706, tid: 5706, name: logPrintCppStyl  >>> logPrintCppStyle <<<
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : uid: 0
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : Abort message: 'Check failed: false == true (false=0, true=1) '
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x0  0000000000000000  x1  000000000000164a  x2  0000000000000006  x3  0000007fde3c3c90
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x4  000000000000000a  x5  000000000000000a  x6  000000000000000a  x7  7f7f7f7f7f7f7f7f
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x8  00000000000000f0  x9  0000007864688a80  x10 0000000000000001  x11 00000078646c9760
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x12 0000007fde3c2f74  x13 0000000000000002  x14 0000000000000000  x15 000000786468c8e2
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x16 0000007864736d58  x17 00000078647122a0  x18 0000007868288000  x19 000000000000164a
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x20 000000000000164a  x21 00000000ffffffff  x22 0000007867a27000  x23 00000058c8e3fb8e
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x24 00000058c8e3fc17  x25 00000058c8e3fc1a  x26 00000058c8e3fc6c  x27 00000058c8e3fbb3
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x28 00000058c8e3fc8c  x29 0000007fde3c3d10
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     lr  00000078646ba248  sp  0000007fde3c3c70  pc  00000078646ba274  pst 0000000000001000
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : backtrace:
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #00 pc 0000000000053274  /apex/com.android.runtime/lib64/bionic/libc.so (abort+164) (BuildId: 2909e25171905ab2aa55000ddb487289)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #01 pc 00000000000063fc  /system/lib64/liblog.so (__android_log_default_aborter+12) (BuildId: ea3eb93b960dede93d1fb67c42ed7273)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #02 pc 0000000000016a50  /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+352) (BuildId: 805c1dfe4ea9454d03b5d1626665b3f0)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #03 pc 000000000000131c  /system/bin/logPrintCppStyle (main+700) (BuildId: dc17c42573ba586fece229f605ff661a)
     *       11-27 12:37:17.726  5709  5709 F DEBUG   :       #04 pc 000000000004b650  /apex/com.android.runtime/lib64/bionic/libc.so (__libc_init+96) (BuildId: 2909e25171905ab2aa55000ddb487289)
    */
    CHECK_EQ(false, true);
    return EXIT_SUCCESS;
}

上面的例子大致包含了如下几种用法
a)使用接口SetLogger设置log的输出位置，其中 InitLogging 的功能和它是类似的，只不过更加自由，可以重新设置abort级别的log输出。
b)输出各级别的log
c)PLOG的使用，这个还是比较有意思的，因为他会直接把错误码直接转换成人类可阅读的形式输出log，下面是例子

    /**
     * 5. using PLOG to show the detial error when error occurs
     * 11-24 19:17:49.677  2941  2941 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
    */
    open("/dev/fakeDev", O_APPEND);
    PLOG(ERROR) << "PLOG(ERROR):write log";

d)FATAL级别和CHECK_XX系列的接口，前者会直接造成程序进入abort分支，导致程序异常退出。后者在条件满足的条件下和前者表现完全一致

    /**
     * 8.
     *   11-27 12:37:17.677  5706  5706 V logPrintCppStyle: LOG(VERBOSE):write log
     *   11-27 12:37:17.677  5706  5706 D logPrintCppStyle: LOG(DEBUG):write log
     *   11-27 12:37:17.677  5706  5706 I logPrintCppStyle: LOG(INFO):write log
     *   11-27 12:37:17.678  5706  5706 W logPrintCppStyle: LOG(WARNING):write log
     *   11-27 12:37:17.678  5706  5706 E logPrintCppStyle: LOG(ERROR):write log
     *   11-27 12:37:17.678  5706  5706 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
     *   11-27 12:37:17.678  5706  5706 I logPrintCppStyle: set StdioLogger as Logger...
     *   11-27 12:37:17.687  5706  5706 F logPrintCppStyle: Check failed: false == true (false=0, true=1)
     * error information:
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Build fingerprint: 'Fake/full_board_t/board:13/TP1A.220624.014/eng.flagstaff.20220920.145750:userdebug/test-keys'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Revision: '0'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : ABI: 'arm64'
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Timestamp: 2022-11-27 12:37:17.707826659+0800
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Process uptime: 1s
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : Cmdline: logPrintCppStyle
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : pid: 5706, tid: 5706, name: logPrintCppStyl  >>> logPrintCppStyle <<<
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : uid: 0
     *       11-27 12:37:17.724  5709  5709 F DEBUG   : tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : Abort message: 'Check failed: false == true (false=0, true=1) '
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x0  0000000000000000  x1  000000000000164a  x2  0000000000000006  x3  0000007fde3c3c90
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x4  000000000000000a  x5  000000000000000a  x6  000000000000000a  x7  7f7f7f7f7f7f7f7f
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x8  00000000000000f0  x9  0000007864688a80  x10 0000000000000001  x11 00000078646c9760
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x12 0000007fde3c2f74  x13 0000000000000002  x14 0000000000000000  x15 000000786468c8e2
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x16 0000007864736d58  x17 00000078647122a0  x18 0000007868288000  x19 000000000000164a
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x20 000000000000164a  x21 00000000ffffffff  x22 0000007867a27000  x23 00000058c8e3fb8e
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x24 00000058c8e3fc17  x25 00000058c8e3fc1a  x26 00000058c8e3fc6c  x27 00000058c8e3fbb3
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     x28 00000058c8e3fc8c  x29 0000007fde3c3d10
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :     lr  00000078646ba248  sp  0000007fde3c3c70  pc  00000078646ba274  pst 0000000000001000
     *       11-27 12:37:17.725  5709  5709 F DEBUG   : backtrace:
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #00 pc 0000000000053274  /apex/com.android.runtime/lib64/bionic/libc.so (abort+164) (BuildId: 2909e25171905ab2aa55000ddb487289)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #01 pc 00000000000063fc  /system/lib64/liblog.so (__android_log_default_aborter+12) (BuildId: ea3eb93b960dede93d1fb67c42ed7273)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #02 pc 0000000000016a50  /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+352) (BuildId: 805c1dfe4ea9454d03b5d1626665b3f0)
     *       11-27 12:37:17.725  5709  5709 F DEBUG   :       #03 pc 000000000000131c  /system/bin/logPrintCppStyle (main+700) (BuildId: dc17c42573ba586fece229f605ff661a)
     *       11-27 12:37:17.726  5709  5709 F DEBUG   :       #04 pc 000000000004b650  /apex/com.android.runtime/lib64/bionic/libc.so (__libc_init+96) (BuildId: 2909e25171905ab2aa55000ddb487289)
    */
    CHECK_EQ(false, true);

4.使用属性控制log级别输出

打印到logd中的log和C语言形式的log一样，也是支持根据log级别做有选择的方式进行输出的。但对于输出到标准输出以及kmsg的情况则是不适用的。

board:/ # setprop log.tag.logPrintCppStyle V
board:/ # logPrintCppStyle
LOG(INFO):write log
11-27 17:20:19.197  5914  5914 V logPrintCppStyle: LOG(VERBOSE):write log
11-27 17:20:19.197  5914  5914 D logPrintCppStyle: LOG(DEBUG):write log
11-27 17:20:19.197  5914  5914 I logPrintCppStyle: LOG(INFO):write log
11-27 17:20:19.197  5914  5914 W logPrintCppStyle: LOG(WARNING):write log
11-27 17:20:19.197  5914  5914 E logPrintCppStyle: LOG(ERROR):write log
11-27 17:20:19.197  5914  5914 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
11-27 17:20:19.197  5914  5914 I logPrintCppStyle: set StdioLogger as Logger...
11-27 17:20:19.206  5914  5914 F logPrintCppStyle: Check failed: false == true (false=0, true=1)
Aborted
board:/ # setprop log.tag.logPrintCppStyle E
board:/ # logPrintCppStyle
11-27 17:20:24.767  5923  5923 E logPrintCppStyle: LOG(ERROR):write log
11-27 17:20:24.767  5923  5923 E logPrintCppStyle: PLOG(ERROR):write log: No such file or directory
11-27 17:20:24.775  5923  5923 F logPrintCppStyle: Check failed: false == true (false=0, true=1)
Aborted