This is a creation in Article, where the information may have evolved or changed. The purpose of writing this series is not to list all the features of the debugger for the Golang programming language. If you want to see these things, you can look at [Delve] (https://github.com/derekparker/delve). In this article we try to explore how the debugger usually works, how to do a basic debugging on Linux, Linux is more concerned about the function of Golang, such as [Goroutine] (https://golang.org/ref/spec#Go_ statements). Creating a debugger is not that simple. On this topic we can not finish a single article. Instead, this blog post is a start, and the ultimate goal of this series is to find a solution to handle the most common scenarios. During the period we will discuss similar [ELF] (Https://pl.wikipedia.org/wiki/Executable_and_Linkable_Format), [DWARF] (https://en.wikipedia.org/ WIKI/DWARF), there are also some architectural-related issues to be contacted. # # Environment # #整个系列文章中, we'll use [Docker] (https://www.docker.com/) to get a copy of the playground based on Debian Jessie. I'm using [x86-64] (https://en.wikipedia.org/wiki/X86-64), which can be a bit of a starting point for us to do some bottom-up discussions. The project structure is as follows: "' > Tree.├──dockerfile└──src└──github.com└──mlowicki├──debugger│└──debugger.go└──hello└──hello.go '" The main file of the debugger we're going to use right away is the *debugger.go*,*hello.go* file that contains the sample program source code that we debugged throughout our process. Now you can write the simplest of things: "' gopackage mainfunc Main () {}" We'll write a very simple Dockerfile: ' from Golang:1.8.1run apt-get update & & Apt-get install-y Tree "to compile the Docker image to (DockerThe outermost directory where file is located, run: ' > Docker build-t godebugger. ' To container acceleration, execute: ' > Docker run--rm-it-v "$PWD"/src:/go/src--secu rity-opt seccomp=unconfined Godebugger "[here] (https://docs.docker.com/engine/security/seccomp/) There is a description of the safe operation mode (SECCOMP). Now all that is left is to compile these two programs in the container. The first one can do this: "> Go install--gcflags="-n-l "Github.com/mlowicki/hello" logo--gcflag used to suppress [inline function] (https:// En.wikipedia.org/wiki/inline_expansion) (-L), compile-optimized (-N) to make debugging easier. The debugger compiles as follows: ' > Go install Github.com/mlowicki/debugger ' contains '/go/bin ' in the container's environment variable *path*, so that you can run any newly compiled program without using the full path. Whether it's ' hello ' or ' debugger '. [] (https://raw.githubusercontent.com/studygolang/gctt-images/master/making-debugger/1_ Lkltdwon2t9n4melhrdvag.jpeg) # # # The first step # #我们的第一个任务很简单. Stop the program before executing any instructions, and then run it again until the program stops (whether it is automatically stopped or an error stop occurs). Most debuggers you can start with. Set some tracking points (breakpoints), and then perform a command like ' continue ' to actually run until you stop where you want to stop. Let's see how [Delve] (Https://github.com/derekparker/delve) works: "Shell> cat hello.gopackage Mainimport" FMT "Func f () int {var n intn = 1n = 2return N}func main () {FMT. Println (f ())}> DLV debugbreak Type ' help ' for list of commands. (DLV) Break Main.fbreakpoint 1 SET @ 0x1087050 for MAIN.F ()./hello.go:5 (DLV) continue> main.f ()./hello.go:5 (hits Go Routine (1): 1 total:1) (pc:0x1087050) 1:package main 2:3: Import "FMT" 4:=> 5:func f () int {6:var n int 7:n = 1 8 : n = 2 9:return N10:} (DLV) next> main.f ()./hello.go:6 (pc:0x1087067) 1:package main 2:3: Import "FMT" 4:5: Func f () int {=> 6:var n int 7:n = 1 8:n = 2 9:return n10:}11: (DLV) print n842350461344 (DLV) next> main.f ()./hello . Go:7 (pc:0x108706f) 2:3: Import "FMT" 4:5: Func f () int {6:var n int=> 7:n = 1 8:n = 2 9:return n10:}11:12:f UNC Main () {(DLV) print n0 (DLV) next> main.f ()./hello.go:8 (pc:0x1087077) 3:import "FMT" 4:5: Func f () int {6:var n int 7:n = 1=> 8:n = 2 9:return N10:}11:12:func main () {13:fmt. Println (f ()) (DLV) Print N1 "Let's see how we do it ourselves." The first step is to find a mechanism for the process (our debugger) to control the other processes (the process we are debugging). Fortunately on Linux we have this--[Ptrace] (http://man7.org/linux/man-pages/man2/ptrace.2.html). That's not the count. Golang's [Syscall] (https://golang.org/pkg/syscall/) package provides a similar [Ptracecont] (https://golang.org/pkg/syscall/# Ptracecont) interface, you can restart the process being traced. So here's the second part, but in order to have the opportunity to set breakpoints before the program starts executing, we have to do something else. When creating a new process we can specify the process behavior by setting properties-[Sysprocattr] (https://golang.org/pkg/syscall/#SysProcAttr). One is that *ptrace* can track the process, and then the process stops and sends a [SIGSTOP signal] (http://man7.org/linux/man-pages/man7/signal.7.html) to the parent process before it is opened. We have just learned the content into a workflow ... ' shell> cat src/github.com/mlowicki/hello/hello.gopackage mainimport "FMT" Func Main () { Fmt. Println ("Hello World")}> cat Src/github.com/mlowicki/debugger/debugger.gopackage mainimport ("Flag" "Log" "OS" "os/ Exec "" Syscall ") func main () {flag. Parse () Input: = flag. ARG (0) cmd: = exec. Command (input) cmd. Args = []string{input}cmd. Stdout = OS. Stdoutcmd.stderr = OS. Stderrcmd.sysprocattr = &syscall. Sysprocattr{ptrace:true}err: = cmd. Start () if err! = Nil {log. Fatal (err)}err = cmd. Wait () log. Printf ("state:%v\n", err) log. PRINTLN ("Restarting ...") Err = Syscall. Ptracecont (cmd. ProcEss. Pid, 0) if err! = Nil {log. Panic (err)}var ws syscall. Waitstatus_, err = Syscall. WAIT4 (cmd. Process.pid, &ws, Syscall. WALL, nil) if err! = Nil {log. Fatal (Err)}log. Printf ("Exited:%v\n", WS. Exited ()) log. Printf ("Exit Status:%v\n", WS. Exitstatus ())}> go install-gcflags= "-n-l" github.com/mlowicki/hello> Go install Github.com/mlowicki/debugger > debugger/go/bin/hello2017/05/05 20:09:38 state:stop signal:trace/breakpoint trap2017/05/05 20:09:38 Restarting ... hello world2017/05/05 20:09:38 exited:true2017/05/05 20:09:38 Exit status:0 ' The first version of the debugger is implemented in a simple way. A tracked process is started, and then the process stops before executing the first instruction and sends a signal to the parent process. The parent process waits for this signal and logs ' log '. Printf ("state:%v\n", err) '. After the program restarts, the parent process waits for it to terminate. This way we have the opportunity to set breakpoints ahead of time, start the program, wait for the specified track point, look at the current value like the Stack or registry, check the status of the process. [] (Https://raw.githubusercontent.com/studygolang/gctt-images/master/making-debugger/1_qysN9I7NtfurG2K7kT_ 1SW.JPEG) Even if we know a little bit, we can do some great things. These will lay the groundwork for future improvements and practices (in the near future). Give us some praise, so that more people can see this article. If you want to get post updates or get improved at work, follow us.
Via:https://medium.com/golangspec/making-debugger-for-golang-part-i-53124284b7c8
Author: Michałłowicki Translator: arisaries proofreading: polaris1119
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