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https://github.com/jbranchaud/til
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64 lines
2.6 KiB
Markdown
64 lines
2.6 KiB
Markdown
# Basic Delve Debugging Session
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When using [delve](https://github.com/go-delve/delve) to debug a Go program,
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these are the series of things I usually find myself doing.
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First, I start running the program with `dlv` including any arguments after a `--` (in my case, the `solve` subcommand and a filename).
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```bash
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$ dlv debug . -- solve samples/001.txt
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```
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`dlv` starts up and is ready to run my program from the beginning. I'll need to
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set a couple breakpoints before continuing. I do this with the `break` command,
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specifying the filename and line number.
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```
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(dlv) break main.go:528
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Breakpoint 1 set at 0x10c1a5bea for main.traversePuzzleIterative() ./main.go:528
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(dlv) break main.go:599
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Breakpoint 2 set at 0x10c1a6dcc for main.traversePuzzleIterative() ./main.go:599
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```
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Now I can continue which will run the program until hitting a breakpoint.
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```
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(dlv) continue
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> [Breakpoint 2] main.traversePuzzleIterative() ./main.go:599 (hits goroutine(1):1 total:1) (PC: 0x10c1a6dcc)
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594: }
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595: }
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596:
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597: topStackFrame := stack[len(stack)-1]
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598: // if the current stack frame has more values, try the next
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=> 599: if len(topStackFrame.PossibleValues) > 0 {
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600: nextValue := topStackFrame.PossibleValues[0]
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601: topStackFrame.PossibleValues = topStackFrame.PossibleValues[1:]
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602: topStackFrame.CurrValue = nextValue
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603:
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604: // Undo the last placement and make a new one
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```
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I can see the context around the line we've stopped on. From here I can dig
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into the current state of the program by looking at local variables (`locals`)
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or printing out a specific value (`print someVar`). I can continue to step
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through the program line by line with `next` or eventually run `continue` to
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proceed to the next breakpoint.
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```
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(dlv) locals
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diagnostics = main.Diagnostics {BacktrackCount: 0, NodeVisitCount: 1, ValidityCheckCount: 2,...+2 more}
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stack = []main.StackData len: 1, cap: 1, [...]
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emptyCellPositions = [][]int len: 3, cap: 4, [...]
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emptyCellIndex = 1
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status = "Invalid"
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topStackFrame = main.StackData {RowIndex: 1, ColumnIndex: 7, PossibleValues: []int len: 8, cap: 8, [...],...+1 more}
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(dlv) print topStackFrame
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main.StackData {
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RowIndex: 1,
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ColumnIndex: 7,
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PossibleValues: []int len: 8, cap: 8, [2,3,4,5,6,7,8,9],
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CurrValue: 1,}
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(dlv) next
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> main.traversePuzzleIterative() ./main.go:600 (PC: 0x10c1a6dea)
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```
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