Add Basic Delve Debugging Session as a Go TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1555 TILs and counting..._
+_1556 TILs and counting..._
 
 ---
 
@@ -403,6 +403,7 @@ _1555 TILs and counting..._
 
 - [Access Go Docs Offline](go/access-go-docs-offline.md)
 - [Add A Method To A Struct](go/add-a-method-to-a-struct.md)
+- [Basic Delve Debugging Session](go/basic-delve-debugging-session.md)
 - [Build For A Specific OS And Architecture](go/build-for-a-specific-os-and-architecture.md)
 - [Check If Cobra Flag Was Set](go/check-if-cobra-flag-was-set.md)
 - [Combine Two Slices](go/combine-two-slices.md)

go/basic-delve-debugging-session.md

@@ -0,0 +1,63 @@
+# Basic Delve Debugging Session
+
+When using [delve](https://github.com/go-delve/delve) to debug a Go program,
+these are the series of things I usually find myself doing.
+
+First, I start running the program with `dlv` including any arguments after a `--` (in my case, the `solve` subcommand and a filename).
+
+```bash
+$ dlv debug . -- solve samples/001.txt
+```
+
+`dlv` starts up and is ready to run my program from the beginning. I'll need to
+set a couple breakpoints before continuing. I do this with the `break` command,
+specifying the filename and line number.
+
+```
+(dlv) break main.go:528
+Breakpoint 1 set at 0x10c1a5bea for main.traversePuzzleIterative() ./main.go:528
+(dlv) break main.go:599
+Breakpoint 2 set at 0x10c1a6dcc for main.traversePuzzleIterative() ./main.go:599 
+```
+
+Now I can continue which will run the program until hitting a breakpoint.
+
+```
+(dlv) continue
+> [Breakpoint 2] main.traversePuzzleIterative() ./main.go:599 (hits goroutine(1):1 total:1) (PC: 0x10c1a6dcc)
+   594:                                 }
+   595:                         }
+   596:
+   597:                         topStackFrame := stack[len(stack)-1]
+   598:                         // if the current stack frame has more values, try the next
+=> 599:                         if len(topStackFrame.PossibleValues) > 0 {
+   600:                                 nextValue := topStackFrame.PossibleValues[0]
+   601:                                 topStackFrame.PossibleValues = topStackFrame.PossibleValues[1:]
+   602:                                 topStackFrame.CurrValue = nextValue
+   603:
+   604:                                 // Undo the last placement and make a new one
+```
+
+I can see the context around the line we've stopped on. From here I can dig
+into the current state of the program by looking at local variables (`locals`)
+or printing out a specific value (`print someVar`). I can continue to step
+through the program line by line with `next` or eventually run `continue` to
+proceed to the next breakpoint.
+
+```
+(dlv) locals
+diagnostics = main.Diagnostics {BacktrackCount: 0, NodeVisitCount: 1, ValidityCheckCount: 2,...+2 more}
+stack = []main.StackData len: 1, cap: 1, [...]
+emptyCellPositions = [][]int len: 3, cap: 4, [...]
+emptyCellIndex = 1
+status = "Invalid"
+topStackFrame = main.StackData {RowIndex: 1, ColumnIndex: 7, PossibleValues: []int len: 8, cap: 8, [...],...+1 more}
+(dlv) print topStackFrame
+main.StackData {
+        RowIndex: 1,
+        ColumnIndex: 7,
+        PossibleValues: []int len: 8, cap: 8, [2,3,4,5,6,7,8,9],
+        CurrValue: 1,}
+(dlv) next
+> main.traversePuzzleIterative() ./main.go:600 (PC: 0x10c1a6dea)
+```