Useful Go Delve Debugger commands

go-dlv-note.md

Particularly Useful Delve Commands for Go Debugging

You might find invaluable during Go debugging sessions:

1. Breakpoint Commands:

b or break main.go:34    - Set breakpoint at line 34
bp or breakpoints        - List all breakpoints
clear 1                  - Remove breakpoint #1
clearall                 - Remove all breakpoints
condition <bp> <expr>    - Set breakpoint condition

2. Execution Control:

c or continue           - Run until breakpoint
n or next              - Step over (execute current line)
s or step              - Step into function
stepout                - Step out of current function
restart                - Restart the debugging session

3. Variable Inspection:

p or print <var>       - Print variable value
whatis <var>          - Show variable type
vars                  - Display local variables
locals                - Show all local variables
args                  - Show function arguments

examples

# Print a variable value
p myVariable
p users[0].Name

# Print struct with all fields
print %x myStruct

# Show type information
whatis myVariable

# Show all local variables in current function
locals

# Print slice/array with 4 elements per line
p -l 4 mySlice

4. Goroutine Management:

goroutines            - List all goroutines
goroutine            - Show current goroutine
gr <id>              - Switch to specific goroutine

examples

# List all goroutines with their states
goroutines

# Show details of current goroutine
goroutine

# Switch to goroutine #12
gr 12

# Show goroutines with specific filter
goroutines -t    # Show only running goroutines
goroutines -s    # Show start location

5. Stack Manipulation:

bt or stack           - Print stack trace
frame <n>            - Select frame by number
up                   - Move up one frame
down                 - Move down one frame

6. Data Structure Navigation:

set <variable> = <value>  - Change variable value
examinemem <addr>         - Examine memory
display                   - Print value of an expression each time program stops

7. Function-related:

funcs <pattern>      - List functions matching pattern
list                - Show source code around current point
disassemble         - Disassemble current function

examples

# List all functions containing "handler"
funcs handler

# List all methods of a struct
funcs MyStruct

# Show current function source
list

# Show specific lines of code
list 15:20

8. Process Control:

exit or quit        - Exit debugger
restart             - Restart process
on <event> <cmd>    - Execute command when event occurs

Particularly useful advanced techniques:

# Conditional breakpoints
break main.go:34 -c "someVar == 5"

# Break on function
break MyFunction

# Watch variables
watch someVariable

# Print with format
p -f hex someValue    # Print in hexadecimal

Application Inspection

# Show stack trace with full argument values
stack -full

# Show all threads
threads

# Memory statistics
memstats

# Check current package/function
frame

# Register values
regs

Runtime Debugging

# Set dynamic breakpoint on function entry
b MyFunction

# Break when variable changes
watch myVariable

# Break with condition
b main.go:35 -c "err != nil"

# Print every time a variable changes
display myVariable

Quick Reference for Common Debugging Flow

# Start debugging
dlv debug ./cmd/myapp/main.go

# Set initial breakpoint
b main.main

# Run until breakpoint
continue (or c)

# Step through code
next (or n)    # Step over
step (or s)    # Step into
stepout        # Step out of function

# Examine state
bt             # Show stack trace
p variableName # Print variable
whatis v       # Show variable type

Pro Tips: 0. Use ctrl+d to exit delve

1. You can use help <command> to get detailed information about any command
2. Use config to set various debugger configurations
3. The source command can load a file containing delve commands
4. Use trace to set tracepoints that don't stop execution but print information
5. The on command is powerful for automating debugging tasks
6. Up/down arrow keys navigate command history And finally Use clear to remove breakpoints when they're no longer needed.

Happy Debugging!