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68 lines
2.0 KiB
Markdown
68 lines
2.0 KiB
Markdown
---
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title: Debugging [GDB]
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description:
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draft: false
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tags:
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- programming
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author: TrudeEH
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showToc: true
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---
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## GDB Debugging
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### Compile with Debug Information
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To allow `gdb` access to the source code (Provides debug symbols - Do not share publicly as it contains the source code).
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```Shell
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gcc -g <file>
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```
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### Look for / Fix Bugs
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First, initialize `gdb` with the executable to debug.
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```Shell
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gdb ./<executable> --tui
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```
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After `gdb` is ready, we can use the following commands:
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|Command|Description|
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|---|---|
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|`lay next`|Switch to the next layout (Enables TUI mode if disabled - Allows for reading the code while debugging both in `C` and `ASM`).|
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|`ref`|Refresh (if a program prints to the terminal, it can break `gdb`'s interface).`|
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|`q`|Quit `gdb`.|
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|`b main`|Add a breakpoint at the main function.|
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|`b`|Place a breakpoint at the current line.|
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|`b <N>`|Place a breakpoint at line `N`.|
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|`b +<N>`|Place a breakpoint N lines down.|
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|`b <fn>`|Place a breakpoint at `fn` function.|
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|`d`|Delete all breakpoints.|
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|`d <N>`|Delete breakpoint number `N`.|
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|`clear <fn>`|Clear the breakpoint set to `fn` function.|
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|`n`|Execute up to the next line in `C`. If a function call is found, execute the function completely.|
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|`s`|Execute up to the next line in `C`. (Jump over)|
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|`s <N>`|Run `N` lines.|
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|`u`|Same as `n`, but if in a loop, execute until the loop exits.|
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|`nexti`|Execute up to the next instruction (line in `ASM`).|
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|`r`|Run the program until a breakpoint or error is reached.|
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|`c`|Continue running the program until a breakpoint or error is reached.|
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|`x/i $pc`|Examine the previous instruction (View memory).|
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|`info registers`|Read the CPU registers used by the program.|
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|`bt`|See the call stack up to the current line. (How we got here, so to speak)|
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|`print sizeof(<variable>)`|Check the size of a struct/variable/pointer.|
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|`p <var>`|Print variable `var` value.|
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|`info break`|List breakpoints.|
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## Check for Memory Leaks
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Use `valgrind` to check for lost memory.
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```Shell
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valgrind --leak-check=full ./<executable>
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```
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