Curl just ran into two unrelated compiler bugs that only misbehave on ARM64, one in GCC and one in Rust.
Curl's maintainer, posting as @bagder on Mastodon, flagged the pair on October 6, 2026. One bug lives in GCC versions 15 and 16, the other in the Rust compiler, and both are specific to the ARM64 architecture. Neither is a flaw in curl's own source: they are optimization bugs in the compilers themselves, the kind of problem where the code looks correct and the compiler quietly generates something else. The report has stayed relatively quiet online so far, picking up 12 points and two comments on Hacker News.
That quiet reception undersells the point. Compiler bugs are nearly impossible to catch through code review, because nothing in the source is actually wrong, and curl ships inside an enormous range of devices, from phones to servers to routers, that increasingly run on ARM64 chips. Two such bugs turning up in two different toolchains, in the same piece of software, in the same stretch of time, says less about GCC or Rust being unusually broken and more about how much ARM64 code is now getting compiled, tested, and shipped for the first time.
ARM64 has gone from niche to default across phones, laptops, and cloud servers in just a few years, and bugs like these are the toll for that speed.