Occasional off-by-one in the line numbers of runtime.Func.FileLine() #1100
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> (BTW, is there a simple way to get $GOOS and $GOARCH now that they are optional since release.2010-08-25?) Thanks. I changed the questions to ask for the compiler name and operating system. Thanks for these reports. It would help if you could send programs that use package main and define a main function, so they are easier to run. This is actually working as intended. It's a subtle thing, but runtime.Callers returns the return PCs going up the stack. The return PCs are the PCs of the instruction that the call returns to, not the call itself. The code that formats the traceback for a crash subtracts 1 from each PC before translating it to a line number. The equivalent change in your code would be to call f.FileLine(pc - 1). runtime.Callers could lie and do the subtraction, but this is pretty subtle already and I think it's clearer for all involved to hand out the raw data and let clients adjust. Otherwise the clients who want the return PCs have to add 1, and then if that changes they're all broken, and so on and so on. Owner changed to r...@golang.org. Status changed to WorkingAsIntended. |
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by esko.luontola:
What steps will reproduce the problem? package gospec import ( "testing" "runtime" "fmt" ) func TestLineNumbersOfFuncFileLine(t *testing.T) { defer func() { if cause := recover(); cause != nil { callers := make([]uintptr, 100) count := runtime.Callers(0, callers) callers = callers[0:count] for _, pc := range callers { f := runtime.FuncForPC(pc) name := f.Name() file, line := f.FileLine(pc) fmt.Printf("%v %v:%v\n", name, file, line) } } }() var x *Foo = nil x.Fail() } func TestLineNumbersOfPanic(t *testing.T) { var x *Foo = nil x.Fail() } type Foo struct { x string } func (this *Foo) Fail() string { return this.x } What is the expected output? The line number of sigpanic in file runtime/linux/thread.c should be 286 in both stack traces. What do you see instead? panicstring /home/orfjackal/go/src/pkg/runtime/runtime.c:83 sigpanic /home/orfjackal/go/src/pkg/runtime/linux/thread.c:287 gospec.*Foo·Fail /home/orfjackal/devel/gospec/src/gospec/bug_test.go:42 ... panicstring+0x69 /home/orfjackal/go/src/pkg/runtime/runtime.c:83 panicstring(0x48ded8, 0x2b207ce90850) sigpanic+0x148 /home/orfjackal/go/src/pkg/runtime/linux/thread.c:286 sigpanic() gospec.*Foo·Fail+0x18 /home/orfjackal/devel/gospec/src/gospec/bug_test.go:42 gospec.*Foo·Fail(0x4166e1, 0x0, 0x2b207ce8bcf0, 0x2b207ce8bcf0) What is your $GOOS? $GOARCH? linux amd64 (BTW, is there a simple way to get $GOOS and $GOARCH now that they are optional since release.2010-08-25?) Which revision are you using? (hg identify) 97ccc7fb2173 tip Please provide any additional information below. This might be related to https://golang.org/issue/754The text was updated successfully, but these errors were encountered: