zig-debugging

Zig 调试

目的

指导 Agent 调试 Zig 程序：GDB/LLDB 会话、解读 Zig panic 和错误返回跟踪、使用 std.debug.print 记录日志、调试构建配置以及 IDE 集成。

触发条件

• “如何使用 GDB 调试 Zig 程序？”
• “如何解读 Zig panic 消息？”
• “如何使用 std.debug.print 进行调试？”
• “Zig 显示了错误返回跟踪——这是什么意思？”
• “如何在 VS Code 中设置 Zig 调试？”
• “如何获取 Zig 崩溃时的堆栈跟踪？”

工作流

1. 为调试构建

# Debug build (default) — full debug info, safety checks
zig build-exe src/main.zig -O Debug

# With build system
zig build            # uses Debug by default
zig build -Doptimize=Debug

# Run directly with debug output
zig run src/main.zig

2. 使用 GDB 调试 Zig

Zig 会生成与 GDB 兼容的标准 DWARF 调试信息：

# Build with debug info
zig build-exe src/main.zig -O Debug -femit-bin=myapp

# Launch GDB
gdb ./myapp

# GDB session
(gdb) break main
(gdb) run arg1 arg2
(gdb) next          # step over
(gdb) step          # step into
(gdb) continue
(gdb) print my_var
(gdb) info locals
(gdb) bt            # backtrace

在 Zig panic 处设置断点：

(gdb) break __zig_panic_start
(gdb) break std.builtin.default_panic

3. 使用 LLDB 调试 Zig

lldb ./myapp

(lldb) b main
(lldb) r arg1 arg2
(lldb) n            # next
(lldb) s            # step into
(lldb) p my_var     # print
(lldb) frame variable
(lldb) bt           # backtrace
(lldb) c            # continue

# Break on panic
(lldb) b __zig_panic

4. 解读 Zig panic

Zig panic 会包含源代码位置和原因：

thread 'main' panic: index out of bounds: index 5, len 3
/home/user/src/main.zig:15:14
/home/user/src/main.zig:42:9
???:?:?: (name not available)

常见的 panic 消息：

Panic	原因
index out of bounds: index N, len M	切片/数组越界访问
integer overflow	Debug/ReleaseSafe 模式下的算术溢出
attempt to unwrap null	对 null 使用可选值访问 .?
reached unreachable code	执行了 unreachable
casting...	无效的枚举标签或联合体访问
integer cast truncated bits	@intCast 的值超出范围
out of memory	分配器失败

5. 错误返回跟踪

Zig 会通过错误返回跟踪记录错误的传播位置：

error: FileNotFound
/home/user/src/main.zig:30:20: 0x10a3b in openConfig (main)
    const f = try std.fs.openFileAbsolute(path, .{});
                   ^
/home/user/src/main.zig:15:25: 0x10b12 in run (main)
    const cfg = try openConfig("/etc/myapp.conf");
                    ^
/home/user/src/main.zig:8:20: 0x10c44 in main (main)
    try run();
               ^

跟踪会显示错误传播所经过的确切 try 调用链。请从下往上阅读：main → run → openConfig。

在发布构建中启用：

// build.zig
const exe = b.addExecutable(.{
    .name = "myapp",
    .root_source_file = b.path("src/main.zig"),
    .target = target,
    .optimize = optimize,
    .error_tracing = true,  // enable even in ReleaseFast
});

6. 使用 std.debug.print 跟踪

const std = @import("std");

pub fn main() !void {
    const x: u32 = 42;
    const name = "world";

    // Basic print (always to stderr)
    std.debug.print("x = {d}, name = {s}\n", .{ x, name });

    // Print any value (useful for structs)
    const point = Point{ .x = 1, .y = 2 };
    std.debug.print("point = {any}\n", .{point});

    // Formatted output
    std.debug.print("hex: {x}, binary: {b}\n", .{ x, x });

    // Log levels (respects compile-time log level)
    const log = std.log.scoped(.my_module);
    log.debug("debug info: {d}", .{x});
    log.info("started processing", .{});
    log.warn("unusual condition", .{});
    log.err("failed: {s}", .{"reason"});
}

7. std.log 配置

// Override default log level at root
pub const std_options = std.Options{
    .log_level = .debug,  // .debug | .info | .warn | .err
};

// Custom log handler
pub fn logFn(
    comptime level: std.log.Level,
    comptime scope: @TypeOf(.enum_literal),
    comptime format: []const u8,
    args: anytype,
) void {
    const prefix = "[" ++ @tagName(level) ++ "] (" ++ @tagName(scope) ++ "): ";
    std.debug.print(prefix ++ format ++ "\n", args);
}

pub const std_options = std.Options{
    .logFn = logFn,
};

8. VS Code / IDE 集成

安装 zig.vscode-zig 扩展和 CodeLLDB。

.vscode/launch.json：

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Debug Zig",
            "program": "${workspaceFolder}/zig-out/bin/myapp",
            "args": [],
            "cwd": "${workspaceFolder}",
            "preLaunchTask": "zig build"
        }
    ]
}

.vscode/tasks.json：

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "zig build",
            "type": "shell",
            "command": "zig build",
            "group": { "kind": "build", "isDefault": true },
            "problemMatcher": ["$zig"]
        }
    ]
}

相关技能

• 使用 skills/zig/zig-compiler 了解构建模式和调试信息标志
• 使用 skills/debuggers/gdb 了解 GDB 基础知识
• 使用 skills/debuggers/lldb 了解 LLDB 基础知识
• 调试混合 Zig/C 代码时，使用 skills/zig/zig-cinterop