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mohammadmseet-hue wants to merge 2 commits into from
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net/mail: fix quadratic complexity in consumeComment #78393

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net/mail: fix quadratic complexity in consumeComment
mohammadmseet-hue Mar 27, 2026
7742dad
trigger GerritBot commit message rebuild
mohammadmseet-hue Apr 3, 2026
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6 changes: 3 additions & 3 deletions src/net/mail/message.go
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Original file line number Diff line number Diff line change
Expand Up @@ -832,7 +832,7 @@ func (p *addrParser) consumeComment() (string, bool) {
// '(' already consumed.
depth := 1

var comment string
var comment strings.Builder
for {
if p.empty() || depth == 0 {
break
Expand All @@ -846,12 +846,12 @@ func (p *addrParser) consumeComment() (string, bool) {
depth--
}
if depth > 0 {
comment += p.s[:1]
comment.WriteByte(p.s[0])
}
p.s = p.s[1:]
}

return comment, depth == 0
return comment.String(), depth == 0
}

func (p *addrParser) decodeRFC2047Word(s string) (word string, isEncoded bool, err error) {
Expand Down
19 changes: 19 additions & 0 deletions src/net/mail/message_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package mail

import (
"bytes"
"fmt"
"io"
"mime"
"reflect"
Expand Down Expand Up @@ -1260,3 +1261,21 @@ func TestEmptyAddress(t *testing.T) {
t.Errorf(`ParseAddressList("") = %v, %v, want nil, error`, list, err)
}
}

func BenchmarkConsumeComment(b *testing.B) {
for _, n := range []int{10, 100, 1000, 10000} {
b.Run(fmt.Sprintf("depth-%d", n), func(b *testing.B) {
// Build a deeply nested comment: (((...a...)))
open := strings.Repeat("(", n)
close := strings.Repeat(")", n)
// consumeComment expects the leading '(' already consumed,
// so we start with one fewer opening paren and the parser
// will handle nesting from there.
input := open[:n-1] + "a" + close
for b.Loop() {
p := addrParser{s: input}
p.consumeComment()
}
})
}
}