golang/go

cmd/vet: incorrect printf "invalid argument index" with ... argument

Open

#34,007 opened on Sep 1, 2019

View on GitHub
 (2 comments) (1 reaction) (0 assignees)Go (19,008 forks)batch import
AnalysisNeedsFixhelp wanted

Repository metrics

Stars
 (133,883 stars)
PR merge metrics
 (No merged PRs in 30d)

Description

What version of Go are you using (go version)?

tip (79669dc705)

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

darwin/amd64

What did you do?

https://play.golang.org/p/uIeIGQWBhgB

package main

import (
	"fmt"
)

func main() {
	s := []interface{}{"Hello", "playground"}
	fmt.Printf("%[2]s\n", s...)
}

What did you expect to see?

No vet warning.

I think this is a valid program, which prints "playground" as intended. It doesn't seem like a potential bug to me.

What did you see instead?

./prog.go:9:2: Printf format has invalid argument index [2]

Contributor guide

Research direction
Investigate the vet printf checker to understand why it incorrectly reports an invalid argument index for variadic `...` arguments.
Tech stack
go
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Go
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65