Io Writestring Byte Slice

ID

go.io_writestring_byte_slice

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Code Smell

Language

Go

Tags

CWE:1164, code-smell, readability

Description

Reports io.WriteString(w, string(b)) where b is a []byte.

Rationale

io.WriteString exists to write a string without an intermediate byte-slice conversion. Converting a byte slice to a string only to pass it to WriteString allocates a copy of the data and then writes it byte-for-byte; calling w.Write(b) directly avoids the round-trip. The rule fires only when the second argument is a string(…​) conversion of an unnamed []byte; a named byte-slice type or an unresolved value is left alone.

import "io"

func fn(w io.Writer, b []byte) {
    io.WriteString(w, string(b)) // FLAW — use w.Write(b)
    io.WriteString(w, "literal") // OK
}

Remediation

Write the byte slice directly with w.Write(b) instead of converting it to a string.

References