在 macOS 中调试

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2023-12-01

如果你在 Electron 中遇到问题或者引起崩溃，你认为它不是由你的JavaScript应用程序引起的，而是由 Electron 本身引起的。调试可能有点棘手，特别是对于不习惯 native/C++ 调试的开发人员。然而，使用 lldb 和 Electron 源代码，可以在 Electron 的源代码中使用断点启用逐步调试。如果您希望用图形界面的开发工具，也可以使用XCode for debugging。

要求

Electron 的调试版本: 最简单的方法是自己构建它，使用 macOS 的构建说明中列出的工具和先决条件要求。 While you can attach to and debug Electron as you can download it directly, you will find that it is heavily optimized, making debugging substantially more difficult: The debugger will not be able to show you the content of all variables and the execution path can seem strange because of inlining, tail calls, and other compiler optimizations.
Xcode: 除了 Xcode，还安装 Xcode 命令行工具. They include LLDB, the default debugger in Xcode on macOS. It supports debugging C, Objective-C and C++ on the desktop and iOS devices and simulator.

.lldbinit: Create or edit ~/.lldbinit to allow Chromium code to be properly source-mapped.

# e.g: ['~/electron/src/tools/lldb']
script sys.path[:0] = ['<...path/to/electron/src/tools/lldb>']
script import lldbinit

附加并调试 Electron

To start a debugging session, open up Terminal and start lldb, passing a non-release build of Electron as a parameter.

$ lldb ./out/Testing/Electron.app
(lldb) target create "./out/Testing/Electron.app"
Current executable set to './out/Testing/Electron.app' (x86_64).

设置断点

LLDB是一个强大的工具，支持进行多种策略的代码检查。在这做一个基本的介绍，让我们假设你从 JavaScript 调用一个不正常的命令 - 所以你想打断该命令的 C++ 对应的 Electron 源。

Relevant code files can be found in ./shell/.

让我们假设你想调试 app.setName(), 在 browser.cc 中定义为 Browser::SetName(). 使用 breakpoint 命令进行断点，指定文件和断点位置:

(lldb) breakpoint set --file browser.cc --line 117
Breakpoint 1: where = Electron Framework`atom::Browser::SetName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) + 20 at browser.cc:118, address = 0x000000000015fdb4

然后, 启动 Electron:

(lldb) run

应用程式会立即暂停，因为 Electron 会在启动时设定应用程序名称:

(lldb) run
Process 25244 launched: '/Users/fr/Code/electron/out/Testing/Electron.app/Contents/MacOS/Electron' (x86_64)
Process 25244 stopped
* thread #1: tid = 0x839a4c, 0x0000000100162db4 Electron Framework`atom::Browser::SetName(this=0x0000000108b14f20, name="Electron") + 20 at browser.cc:118, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100162db4 Electron Framework`atom::Browser::SetName(this=0x0000000108b14f20, name="Electron") + 20 at browser.cc:118
   115  }
   116
   117  void Browser::SetName(const std::string& name) {
-> 118    name_override_ = name;
   119  }
   120
   121  int Browser::GetBadgeCount() {
(lldb)

显示当前帧的参数和局部变量, 运行 frame variable (或 fr v), 这将显示你的应用程序当前设置名称为 “Electron”.

(lldb) frame variable
(atom::Browser *) this = 0x0000000108b14f20
(const string &) name = "Electron": {
    [...]
}

在当前选择的线程中执行源级单步执行, 执行 step (或 s). 这将带你进入 name_override_.empty()。继续前进，步过，运行 next (或 n).

(lldb) step
Process 25244 stopped
* thread #1: tid = 0x839a4c, 0x0000000100162dcc Electron Framework`atom::Browser::SetName(
    this=0x0000000108b14f20, name="Electron"
) + 44 at browser.cc:119, queue = 'com.apple.main-thread', stop reason = step in
    frame #0: 0x0000000100162dcc Electron Framework`atom::Browser::SetName(
    this=0x0000000108b14f20, name="Electron"
) + 44 at browser.cc:119
   116
   117  void Browser::SetName(const std::string& name) {
   118    name_override_ = name;
-> 119  }
   120
   121  int Browser::GetBadgeCount() {
   122    return badge_count_;

NOTE: If you don't see source code when you think you should, you may not have added the ~/.lldbinit file above.

要完成此时的调试，运行 process continue。你也可以继续，直到这个线程中的某一行被命中(线程直到100)。此命令将在当前帧中运行线程，直到它到达此帧中的行100，或者如果它离开当前帧，则停止。

现在，如果你打开 Electron 的开发工具并调用 setName，你将再次命中断点。

进一步阅读

LLDB是一个强大的工具，有一个庞大的文档。 To learn more about it, consider Apple's debugging documentation, for instance the LLDB Command Structure Reference or the introduction to Using LLDB as a Standalone Debugger.

You can also check out LLDB's fantastic manual and tutorial, which will explain more complex debugging scenarios.