sizeof(long double) differs in Intel vs. ARM64 (ARM64 long doubles are just doubles). How to get extended precision in Apple Silicon?

App & System Services Core OS
ComposerShield OP
Created Feb ’21
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sizeof(long double) is 16 (aka 128 bits) in Intel Macs for alignment purposes but is actually 80 bit precision according to their documentation. In Apple Silicon, long doubles are just doubles. Anybody know how I can get 80 bit precision or better in my ARM64 slice?
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DTS Engineer OP
Apple
Feb ’21
The 80-bit floating point format you’re using is very Intel-specific. It’s not supported on Apple Silicon. AFAICT there’s no built-in support for floating-point numbers larger than Float64. If you absolutely need that, you’ll have to look for a third-party library that does this.

Keep in mind that this will be implemented in software and thus there’ll be a significant performance impact.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
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DTS Engineer OP
Apple
Jun ’21

Agh, sorry, the line feeds did not stick

Indeed. If you put your text into an answer (the Your Answer field) rather than a comment, it’ll be much more readable.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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sizeof(long double) differs in Intel vs. ARM64 (ARM64 long doubles are just doubles). How to get extended precision in Apple Silicon?
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