Bug #22416: Respect timezone abbreviation encodings in `Time#strftime`

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED

[nobu (Nobuyoshi Nakada)]

Time#strftime treats non-ASCII timezone abbreviations as if their bytes use the locale encoding. However, a timezone object's abbr method can return a String in another encoding. In that case, formatting %Z can produce corrupted text or a result with an unexpected encoding.

Timezone objects have been supported since Ruby 2.6.0, so this issue affects Ruby 2.6.0 and later.

Reproduction:

zone = Object.new
def zone.local_to_utc(t) = t
def zone.utc_to_local(t) = t
def zone.abbr(t) = "東京標準時".encode(Encoding::Shift_JIS)

time = Time.new(2020, 1, 1, 0, 0, 0, zone)
result = time.strftime("☆%Z")
p result
p result.encoding

Expected: result contains ☆東京標準時 and is valid UTF-8. Instead, the text may be corrupted because the abbreviation's bytes are interpreted using the locale encoding.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|54cc01ede02b6cca15eeded10842c5d4ab11b9e4.

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[Bug #22416] Respect timezone abbreviation encodings in strftime

Timezone objects can return abbreviations in encodings beyond the
locale. Respect their encoding when formatting %Z to avoid
misinterpreting their bytes.