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Re: strtold does not set errno when it should
- From: Bruno Haible <bruno at clisp dot org>
- To: newlib at sourceware dot org, Corinna Vinschen <corinna-cygwin at cygwin dot com>
- Date: Mon, 16 Dec 2019 11:05:34 +0100
- Subject: Re: strtold does not set errno when it should
- References: <3561570.L6m47ClBex@omega> <20191216091104.GK10310@calimero.vinschen.de>
Hi Corinna,
> The code for strtold is almost verbatim taken from
>
> https://github.com/jwiegley/gdtoa.git
>
> There haven't been any patches upstream.
Probably that's because the code is good enough for ISO C compliance;
however, POSIX [1] adds the "ERANGE upon underflow" requirement,
whereas ISO C only has an "ERANGE upon overflow" requirement.
[1] <https://pubs.opengroup.org/onlinepubs/9699919799/functions/strtod.html>
> diff --git a/newlib/libc/stdlib/strtodg.c b/newlib/libc/stdlib/strtodg.c
> index 013315946c1b..d6fb26ad3b45 100644
> --- a/newlib/libc/stdlib/strtodg.c
> +++ b/newlib/libc/stdlib/strtodg.c
> @@ -1091,6 +1091,10 @@ _strtodg_l (struct _reent *p, const char *s00, char **se, FPI *fpi, Long *exp,
> irv |= STRTOG_Underflow;
> }
> }
> +#ifndef NO_ERRNO
> + if (irv & STRTOG_Underflow)
> + errno = ERANGE;
> +#endif
> if (se)
> *se = (char *)s;
> if (sign)
>
> which seems to do the trick. But, does it make sense? If not, I'd
> really appreciate a patch.
I think it goes in the right direction.
It can be improved a bit, though: The existing code for overflow is careful
to do the errno stuff only when STRTOG_Overflow is being set/added. I.e.
keep this overflow/underflow handling out of the main path, in order not
to slow down the 99.99% of the cases that don't need it.
My attempt to do this would look like the attached patch. Untested.
Bruno
diff --git a/newlib/libc/stdlib/strtodg.c b/newlib/libc/stdlib/strtodg.c
index 0133159..743f60b 100644
--- a/newlib/libc/stdlib/strtodg.c
+++ b/newlib/libc/stdlib/strtodg.c
@@ -348,6 +348,9 @@ rvOK (struct _reent *p, double d, FPI *fpi, Long *exp, __ULong *bits, int exact,
if (k > nb || fpi->sudden_underflow) {
b->_wds = inex = 0;
*irv = STRTOG_Underflow | STRTOG_Inexlo;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
}
else {
k1 = k - 1;
@@ -362,9 +365,15 @@ rvOK (struct _reent *p, double d, FPI *fpi, Long *exp, __ULong *bits, int exact,
if (carry) {
b = increment(p, b);
inex = STRTOG_Inexhi | STRTOG_Underflow;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
}
else if (lostbits)
inex = STRTOG_Inexlo | STRTOG_Underflow;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
}
}
else if (e > fpi->emax) {
@@ -761,6 +770,9 @@ _strtodg_l (struct _reent *p, const char *s00, char **se, FPI *fpi, Long *exp,
rvb->_x[0] = 0;
*exp = emin;
irv = STRTOG_Underflow | STRTOG_Inexlo;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
goto ret;
}
rvb->_x[0] = rvb->_wds = rvbits = 1;
@@ -940,6 +952,9 @@ _strtodg_l (struct _reent *p, const char *s00, char **se, FPI *fpi, Long *exp,
rvb->_wds = 0;
rve = emin;
irv = STRTOG_Underflow | STRTOG_Inexlo;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
break;
}
adj0 = dval(adj) = 1.;
@@ -1083,12 +1098,18 @@ _strtodg_l (struct _reent *p, const char *s00, char **se, FPI *fpi, Long *exp,
if (sudden_underflow) {
rvb->_wds = 0;
irv = STRTOG_Underflow | STRTOG_Inexlo;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
}
else {
irv = (irv & ~STRTOG_Retmask) |
(rvb->_wds > 0 ? STRTOG_Denormal : STRTOG_Zero);
if (irv & STRTOG_Inexact)
irv |= STRTOG_Underflow;
+#ifndef NO_ERRNO
+ errno = ERANGE;
+#endif
}
}
if (se)