Difference between revisions of "GNU Debugger (GDB)"
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= Installation = | = Installation = | ||
| + | == Windows == | ||
| + | On Windows, gdb is a part of MinGW. See [[MinGW]] for more information. | ||
== Ubuntu == | == Ubuntu == | ||
| − | GDB comes | + | GDB comes installed by default on most Unix-like systems, but if it's not installed, you can run the following: |
<syntaxhighlight lang="Bash"> | <syntaxhighlight lang="Bash"> | ||
sudo apt install gdb | sudo apt install gdb | ||
| Line 12: | Line 14: | ||
This section defines simple usage of GDB. It is by no means comprehensive, but it should be sufficient for a fair amount of debugging scenarios. | This section defines simple usage of GDB. It is by no means comprehensive, but it should be sufficient for a fair amount of debugging scenarios. | ||
| − | + | <ol> | |
| − | + | <li>Compile <br> | |
| − | + | You would compile your file as per usual, but attach the g flag: | |
| − | + | <pre>$ cc -g main.c</pre> | |
| + | </li> | ||
| + | <li>Launch | ||
| + | To launch gdb, run the following, where "a.out" is the output of the compile command above | ||
| + | </li> | ||
| + | <li> Configure Debug | ||
| + | See below for useful debugging commands such as adding breakpoints, stepping through functions or printing the values of variables | ||
| + | </li> | ||
| + | <li>Run | ||
| + | Run the program with your added breakpoints by typing the "run" command. | ||
| + | </li> | ||
| + | <li>Finish | ||
| + | To close gdb, you can enter "q" | ||
| + | </li> | ||
| + | </ol> | ||
= GDB Commands = | = GDB Commands = | ||
| Line 29: | Line 45: | ||
|- | |- | ||
|break <line_number> | |break <line_number> | ||
| − | |Adds a breakpoint at the given line number. Other options include | + | |Adds a breakpoint at the given line number. Other options include<br> |
| − | break | + | break <file_name:line_number><br> |
break <file_name:function_name> | break <file_name:function_name> | ||
|- | |- | ||
| Line 37: | Line 53: | ||
|- | |- | ||
|next | |next | ||
| − | |Debugger will execute the next line as single instruction. This includes whole functions | + | |Debugger will execute the next line as single instruction. This includes whole functions<br> |
Can be abbreviated to n. | Can be abbreviated to n. | ||
|- | |- | ||
| Line 66: | Line 82: | ||
|info args | |info args | ||
|Will return information on the arguments passed | |Will return information on the arguments passed | ||
| + | |- | ||
| + | !colspan="2"|Dealing with Pointers | ||
| + | |- | ||
| + | |print *<pointer> | ||
| + | |Prints what the pointer is pointing to | ||
| + | |- | ||
| + | |print &<variable> | ||
| + | |Displays the address of the variable | ||
|- | |- | ||
|} | |} | ||
| − | == | + | == gdb for openOCD == |
| − | See the openOCD page for more details on using it. Here are some additional gdb commands that might be useful when debugging on hardware: | + | See the [[openOCD]] page for more details on using it. Here are some additional gdb commands that might be useful when debugging on hardware: |
{| class="wikitable" | {| class="wikitable" | ||
|monitor <command> | |monitor <command> | ||
| Line 86: | Line 110: | ||
|x/format address | |x/format address | ||
|Reads the contents of address and displays it according to format. | |Reads the contents of address and displays it according to format. | ||
| − | See [http://sourceware.org/gdb/current/onlinedocs/gdb/Memory.html | + | See [http://sourceware.org/gdb/current/onlinedocs/gdb/Memory.html this link] for more. |
|- | |- | ||
|} | |} | ||
Latest revision as of 12:04, 18 August 2020
The GNU Project Debugger (GDB)
Installation[edit]
Windows[edit]
On Windows, gdb is a part of MinGW. See MinGW for more information.
Ubuntu[edit]
GDB comes installed by default on most Unix-like systems, but if it's not installed, you can run the following:
sudo apt install gdb
Usage[edit]
This section defines simple usage of GDB. It is by no means comprehensive, but it should be sufficient for a fair amount of debugging scenarios.
- Compile
You would compile your file as per usual, but attach the g flag:$ cc -g main.c
- Launch To launch gdb, run the following, where "a.out" is the output of the compile command above
- Configure Debug See below for useful debugging commands such as adding breakpoints, stepping through functions or printing the values of variables
- Run Run the program with your added breakpoints by typing the "run" command.
- Finish To close gdb, you can enter "q"
GDB Commands[edit]
Some useful gdb commands include:
| General | |
|---|---|
| help | Shows details about commands |
| Controlling Execution flow | |
| break <line_number> | Adds a breakpoint at the given line number. Other options include break <file_name:line_number> |
| run | Executes the program in gdb |
| next | Debugger will execute the next line as single instruction. This includes whole functions Can be abbreviated to n. |
| step | Runs a single line of code. Will enter into a called function, unlike next.
Can be abbreviated to s. |
| continue | Continues execution until the next breakpoint.
Can be abbreviated to c. |
| finish | If you're in a function which returns at some point, you can use the finish command to execute the program until the end of the function.
It's equivalent to setting a breakpoint at the return line of a function, and then letting the program run. |
| Gathering information | |
| print <variable> | prints the value of a specified variable.
Can be abbreviated to p. |
| info variables | Will give information on all variables, including some that you haven't defined |
| info locals | Will give information on variables in the current scope |
| info args | Will return information on the arguments passed |
| Dealing with Pointers | |
| print *<pointer> | Prints what the pointer is pointing to |
| print &<variable> | Displays the address of the variable |
gdb for openOCD[edit]
See the openOCD page for more details on using it. Here are some additional gdb commands that might be useful when debugging on hardware:
| monitor <command> | [asses <command> directly to openOCD. Allows openOCD commands to be passed through gdb |
| info registers | prints the names and values of the CPU registers |
| info registers rX | Prints the value of the specifed register rX, where X is a number of a register (0-15 in ARM). |
| set $rX=val | sets register X (O-15 in ARM) to the value val |
| x/format address | Reads the contents of address and displays it according to format.
See this link for more. |
