mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-29 19:07:07 -05:00
87 lines
1.7 KiB
Markdown
87 lines
1.7 KiB
Markdown
---
|
|
title: "Debugging and Performance"
|
|
date: 2019-06-15T10:59:30-04:00
|
|
draft: false
|
|
tags: [ "linux" ]
|
|
---
|
|
|
|
I've come to like the GNU Debugger (GDB) and the `perf` tool recently. This post will be a short summary of the various interesting commands you can use.
|
|
|
|
## GNU Debugger
|
|
|
|
To attach gbd to an existing process do the following
|
|
|
|
```bash
|
|
gdb -p pid_of_process
|
|
```
|
|
|
|
Otherwise you can start a new application
|
|
|
|
```bash
|
|
gdb name_of_executable
|
|
```
|
|
|
|
Once it loads it will bring you into it's own `REPL` environment. Usually once this comes up I find it useful to add breakpoints to the program. You can either do it by function name or by line number.
|
|
|
|
```bash
|
|
(gdb) break FunctionName
|
|
```
|
|
|
|
```bash
|
|
(gdb) break code.cpp:81
|
|
```
|
|
|
|
If you just started a new application you can begin running the program with whatever arguments you wish
|
|
|
|
```bash
|
|
(gdb) run -arg1 -arg2
|
|
```
|
|
|
|
If you have attached to a process then you can continue its execution.
|
|
|
|
```bash
|
|
(gdb) continue
|
|
```
|
|
|
|
### Breakpoints
|
|
|
|
If you have set a breakpoint, it will stop the processes' execution when it lands on the breakpoint. From here, we can take a look at what's on the stack, print variables, and do whatever other debugging we wish.
|
|
|
|
**Print variables on stack:**
|
|
|
|
```bash
|
|
(gdb) info locals
|
|
```
|
|
|
|
**Print a specific variable:**
|
|
|
|
```bash
|
|
(gdb) print variable_name
|
|
```
|
|
|
|
**Show backtrace:**
|
|
|
|
```bash
|
|
(gdb) bt
|
|
```
|
|
|
|
**Continue on with program execution:**
|
|
|
|
```bash
|
|
(gdb) continue
|
|
```
|
|
|
|
## Perf
|
|
|
|
I haven't played with `perf` as much but one thing I found that was cool was the `perf top` command. This command gives you samples of which function calls keeps the program the most busy.
|
|
|
|
To attach to a process and show samples:
|
|
|
|
```bash
|
|
perf top -p pid -K
|
|
```
|
|
|
|
|
|
|
|
|
|
|