Date: Thu, 24 Jan 2002 13:52:50 -0700 From: Chad David <davidc@acns.ab.ca> To: arch@freebsd.org Subject: strtod() Message-ID: <20020124135250.A454@colnta.acns.ab.ca>
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After a short discussion with Alfred he recommended that I post
my question here.
On current (as of today) strtod() sets errno to EINVAL even when no error
actually occurs. While I understand that the value of errno is undefined
if an error does not occur, there is confusion when 0.0 is passed and the
conversion is successful.
SUSv2 states that if no conversion can be performed 0.0 is returned, and
error MAY be set to EINVAL; as well, the Solaris interpretation of SUSv2
and c89 say:
"3. If strtod() returns 0.0, one of the following occurred:
a. The "subject sequence" was not an empty string, but
evaluated to 0.0. (In this case, errno will be left
unchanged.)
b. The "subject sequence" was an empty string. (In this
case, the Single UNIX Specification version 2 allows
errno to be set to EINVAL or to be left unchanged.
The C Standard does not specify any specific behavior
in this case.)
c. The "subject sequence" specified a numeric value that
would cause a floating point underflow. (In this
case, errno may be set to ERANGE or may be left
unchanged.)"
The usage notes all so say:
"Because 0 is returned on error and is also a valid return on
success, an application wishing to check for error situa-
tions should set errno to 0, then call strtod(), then check
errno and if it is non-zero, assume an error has occurred."
I'm not saying that just because Solaris chooses to implement the
interface in this way that FreeBSD should, but I do think that there is a
lot of room for introducing (needless) complexity when porting
applications from Solaris (like I am), and that while FreeBSD does not
have to set EINVAL when an error occurs, it should NOT set it when an
error does not occur.
Note that on stable errno does not get set to EINVAL.
Thanks.
--
Chad David davidc@acns.ab.ca
www.FreeBSD.org davidc@freebsd.org
ACNS Inc. Calgary, Alberta Canada
Fourthly, The constant breeders, beside the gain of eight shillings
sterling per annum by the sale of their children, will be rid of the
charge of maintaining them after the first year. - Johnathan Swift
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