Invalid signature for main()

Vulnerability potential	None
DDoS potential	None

Go’s func main in package main must take no parameters and return no value; the compiler rejects any other signature

Impact

In Go, the program entry point must be declared exactly as func main() in package main: no parameters and no results. Declaring it with arguments (func main(args []string)), a return value (func main() int), or as a method or generic function makes the build fail with “func main must have no arguments and no return values”. The consequence is purely a compile error — no binary is produced, so there is no runtime impact. The defect usually reflects habits carried from C (int main(int argc, char **argv)) or other languages; in Go, command-line arguments and exit codes are obtained through different mechanisms.

Vulnerability potential

This defect has no security relevance. The compiler rejects the program, so no faulty executable exists to attack. It is a build-time correctness issue only.

Technical details

The Go runtime calls main.main with no arguments and ignores any return value; the language spec therefore fixes its signature. The toolchain enforces this in the type checker before code generation.

Getting arguments and exit codes the Go way

Command-line arguments are read from os.Args (a []string, where os.Args[0] is the program name), or parsed via the flag package. The process exit status is set with os.Exit(code) (note: os.Exit skips deferred functions), or by letting main return normally for exit code 0. There is no argc/argv parameter and no integer return as in C.

Related constraints

package main must also contain a main function for go build to produce an executable; an init function may exist alongside it but cannot replace it. func main cannot have type parameters.

Catching the issue

The compiler

go build / go vet reject a wrongly-typed main unconditionally; this can never reach a running program, so no runtime tooling is required.

Editor and review

gopls (the Go language server) flags the bad signature in-editor immediately. In review, simply confirm the entry point is func main() with empty parameter and result lists, and that arguments/exit codes go through os.Args/flag and os.Exit.

How to reproduce

Observe that this does not compile: “func main must have no arguments and no return values”.

package main

func main() int { // invalid: main must take no params and return nothing
	return 0
}