Apple migrates the TrueType hinting interpreter from C to Swift

Category: Apple
Status: confirmed
Sources: Swift.org blog, HN discussion
Summary: Apple rewrote the TrueType hinting interpreter from C to memory-safe Swift and shipped it in the fall 2025 releases. The post states the Swift interpreter runs about 13 percent faster than the C code it replaced. Font parsers process untrusted input, making the hinting interpreter a security-critical attack surface that motivated the migration.
Why it matters: A measured performance gain alongside a memory-safety rewrite of a parser handling untrusted data is a concrete data point for C-to-Swift migration of security-sensitive system code.