<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Aug 18, 2024, at 3:19 PM, Fred J. Tydeman <tydeman@tybor.com> wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">On Thu, 15 Aug 2024 18:21:37 -0700 Jim Thomas wrote:</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><blockquote type="cite">On Aug 14, 2024, at 3:28PM, Fred J. Tydeman <tydeman@tybor.com> wrote:<br><br>On Wed, 14 Aug 2024 10:11:55 -0500 (COT) Fred J. Tydeman wrote:<br><blockquote type="cite"><br>Subject: [SC22WG14.26260] Can nan set errno?<br></blockquote><br>7.5 Errors <errno.h> has the general statement:<br><br>The value of errno may be set to nonzero by a library function call<br>whether or not there is an error, provided the use of errno is not<br>documented in the description of the function in this document.<br><br>7.12.2 Treatment of error conditions has several specific statements<br>that apply to all <math.h> functions. So, overrides the 7.5 general<br>statement.<span class="Apple-converted-space"> </span><br><br>nan() is a <math.h> function, but is not a mathematical function.<br>strtod() is not a <math.h> function; but it has words about<br>overflow and underflow in the Returns section (that mirror 7.12.2).<br><br>So, what should happen for<span class="Apple-converted-space"> </span><br>nan("a_very_long_string_________");<br>strtod("NAN(a_very_long_string_________)", nullptr);<br>when the n-char-sequence is longer than what the nan returned can hold?<br></blockquote><br>As stated in the strtod Description (7.24.2.6 #5), "the meaning of the n-char sequence is implementation-defined." In particular, it does not need to be represented in the return NaN. An implementation is free to return the same NaN for all n-char sequences.<br></blockquote><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">OK for the return value.</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">But, is an implementation allowed to indicate an error</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">(either via errno or the FP exception flags)?</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"></div></blockquote><div><br></div>The strtod specification documents the use of errno (7.24.2.6 #12 and 13) which should mean that the functions can’t set errno in other ways. One could quibble about whether “description” in 7.5 means in the general sense or refers to the Description section. For strtod, errno is documented in the Returns section.</div><div><br></div><div>7.12.2 #1<span class="Apple-tab-span" style="white-space:pre"> </span>says "Each function shall execute as if it were a single operation without raising SIGFPE and without generating any of the floating-point exceptions</div><div>"invalid", "divide-by-zero", or "overflow" except to reflect the result of the function. This applies to the <math.h> nan() function which in the case above is equivalent to strtod(). One might argue that this doesn’t fully cover strtod(). </div><div><br></div><div>F.8.7 says "Operations defined in 6.5.1 and functions and macros defined for the standard libraries change floating-point status flags and control modes just as indicated by their specifications (including conformance to ISO/IEC 60559). They do not change flags or modes (so as to be detectable by the user) in any other cases.” So Annex F implementations are not permitted to raise a floating-point exception for the strtod case you mention. </div><div><br></div><div>How far should we go to specify floating-point exceptions for implementations that don’t conform to the Annex F (ISO/IEC 60559) specification for exceptions?</div><div><br></div><div>- Jim Thomas</div><div><br></div><div><blockquote type="cite"><div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">---</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">Fred J. 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