Difference between revisions of "GNU Debugger (GDB)"
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= Usage = | = Usage = | ||
| + | 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 | ||
| + | # Launch | ||
| + | # Create breakpoints | ||
| + | # Execute | ||
| + | |||
| + | = GDB Commands = | ||
| + | Some useful gdb commands include: | ||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | !colspan="2"|General | ||
| + | |- | ||
| + | |help | ||
| + | |Shows details about commands | ||
| + | |- | ||
| + | !colspan="2"|Controlling Execution flow | ||
| + | |- | ||
| + | |break <line_number> | ||
| + | |Adds a breakpoint at the given line number. Other options include | ||
| + | break [file_name]:line_number | ||
| + | break <file_name:function_name> | ||
| + | |- | ||
| + | |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. | ||
| + | |- | ||
| + | !colspan="2"|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 | ||
| + | |- | ||
| + | |} | ||
| + | |||
| + | == Additional gdb commands when using 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: | ||
| + | {| class="wikitable" | ||
| + | |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 [http://sourceware.org/gdb/current/onlinedocs/gdb/Memory.html |this link] for more. | ||
| + | |- | ||
| + | |} | ||
Revision as of 10:48, 24 July 2020
The GNU Project Debugger (GDB)
Contents
Installation
Ubuntu
GDB comes isntalled by default on most Unix-like systems, but if it's not installed, you can run the following:
sudo apt install gdb
Usage
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
- Launch
- Create breakpoints
- Execute
GDB Commands
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 break <file_name:function_name> |
| 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 |
Additional gdb commands when using 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:
| 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. |
