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Message-ID: <c5c08e3b-1e41-36-a0f5-324f4976b8df@esi.com.au> Date: Wed, 19 Jun 2024 17:09:25 +1000 (AEST) From: Damian McGuckin <damianm@....com.au> To: MUSL <musl@...ts.openwall.com> Subject: Re: roundf() (and round(), and ...) Commenting on only part of that: On Tue, 18 Jun 2024, Szabolcs Nagy wrote: > it is unspecified if (uint32_t)a raises inexact exception, > so this will be target and compiler dependent in practice. Yes. Scary. > ieee-754-2008: > > 5.8 Details of conversions from floating-point to integer formats > ... > A language standard that permits implicit conversions or expressions > involving mixed types should require that these be implemented with > the inexact-signaling conversion operations below. IEEE-754 2019 now specifies: The operations for conversion from floating-point to a specific signed or unsigned integer format without signaling the inexact exception are: One of which is: intFormatOf-convertToIntegerTowardZero(source) convertToIntegerTowardZero(x) rounds x to an integral value toward zero. AND The operations for conversion from floating-point to a specific signed or unsigned integer format, signaling if inexact, are: intFormatOf-convertToIntegerExactTowardZero(source) convertToIntegerExactTowardZero(x) rounds x to an integral value toward zero. So, it depends as you say, which of those two operations the compiler uses when it translates: (integral-type) floating-point-expression If indeed the target supports both. > c23: > > F.4 Floating to integer conversion > ... > ... whether conversion of a non-integral floating value raises the > "inexact" floating-point exception is unspecified.[note] > ... > note: In those cases where it matters, library functions can be used > to effect such conversions with or without raising the "inexact" > floating-point exception. Ah, but then such functions are lower down those that we currently name. Thanks - Damian Pacific Engineering Systems International ..... 20D Grose St, Glebe NSW 2037 Ph:+61-2-8571-0847 .. Fx:+61-2-9692-9623 | unsolicited email not wanted here Views & opinions here are mine and not those of any past or present employer
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