gdb

source/_posts/2015-03-14-introduce-to-gdb.markdown

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+---
+layout: post
+title: "Introduce to gdb"
+date: 2015-03-14 22:01:22 +0800
+comments: true
+categories: os, debug
+---
+
+### 0. Purpose
+
+I'm a freshman to use gdb or c, because I mainly use java, but there is some situation for java programer to use gdb tools to solve problem. So I 'mark' this article~
+
+
+### 1. Debug Target
+
+gdb could debug many kinds of programming languages, like c, c++, objective-c, and so on. It doesn't like debug tools in java, we often use it's command-line interface instead of GUI.
+
+Before we start to debug, we should take code compile with debug information. 
+
+for example, using `gcc` we should add `-g` flag
+
+    $ gcc example.c -g -o example
+
+This is the reason why if we want to debug jvm, we must build it with debug info first.
+
+
+### 2. Run as debug
+
+using
+
+    $ gdb ./example
+
+then we enter the gdb-commandline, and we can use `tab` key to complete or list all command
+
+there are some basic command
+
+| command|description
+|--------|------------------
+| dir [directories]| set source code folder 
+| r | run it 
+| b [where] | add a break, where is an express like 'xx_method' or linenum 
+| b [where] if [condition] | break when condition 
+| l | list code 
+|step | step into a method 
+|c| continue 
+|finish| finish current method 
+|p [var name]|watch a variable value 
+|x/? [address] | watch the memory address 
+|dump memory [file] [sadd] [eadd] | dump memory between to address into file 
+|info thread | list threads 
+|info break | list all break 
+|thread [tid]| switch thread 
+|bt | show stacktrace 
+|[enter]| redo last command 
+
+and so on...
+
+
+### 2. Attach to running process
+
+using 
+
+    $ gdb ./example [pid]
+
+to attach to pid process..
+
+
+### 3. Run with coredump file
+
+using 
+
+    $ gdb ./example [coredump file path]
+
+the [previous blog](http://lysu.github.io/blog/2015/03/07/Troubleshooting-tools/) tell some detail of debug coredump file.
+
+
+Also see
+
+- [GDB调试程序](http://blog.csdn.net/haoel/article/details/2879)
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+        
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