Date: Mon, 4 Feb 2013 14:10:02 GMT
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: freebsd-bugs@FreeBSD.org
Subject: Re: kern/175759: Correct data types for fields of struct qm_trace{} from <sys/queue.h>
Message-ID: <201302041410.r14EA1gT065089@freefall.freebsd.org>
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The following reply was made to PR kern/175759; it has been noted by GNATS.
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Andrey Simonenko <simon@comsys.ntu-kpi.kiev.ua>
Cc: FreeBSD-gnats-submit@freebsd.org
Subject: Re: kern/175759: Correct data types for fields of struct qm_trace{}
from <sys/queue.h>
Date: Mon, 4 Feb 2013 18:05:54 +0400
Andrey,
On Fri, Feb 01, 2013 at 03:49:07PM +0200, Andrey Simonenko wrote:
A> > A> 1. File name fields should have "const char *" type.
A> >
A> > Paragraph 6.10.8 of standard says that __FILE__ is "a character string
A> > literal". It doesn't say that it can be referenced only by a pointer
A> > with const qualifier.
A> >
A> > However, the proposed change definitely makes sence.
A>
A> Yes, but values these pointers are pointed to are not expected
A> to be modified and pointing (char *) to __FILE__ will generate above
A> given warning message.
Thanks for sample code.
A> > A> 2. Line number fields should have "long" or "unsigned long" type,
A> > A> considering C99 standard and its values for [U]INT_MAX, __LINE__
A> > A> and #line.
A> >
A> > Paragraph 6.10.8 of standard says that __LINE__ is "an integer constant".
A> >
A> > Paragraph 6.4.4.1 on integer constants says that "The type of an integer
A> > constant is the first of the corresponding list in which its value can
A> > be represented." The corresponding list starts with "int". According to
A> > paragraph 6.10.4 line number can't get bigger that 2147483647 (INT_MAX),
A> > and this value can be represented by int.
A> >
A> > Thus, I don't see where standard says that line number should be long.
A>
A> 5.2.4.2.1 says "Their implementation-defined values shall be equal or
A> greater in magnitude (absolute value) to those shown, with the same sign."
A>
A> -- maximum value for an object of type int
A> INT_MAX +32767 // 2^15-1
A> -- maximum value for an object of type unsigned int
A> UINT_MAX 65535 // 2^16-1
A> -- maximum value for an object of type long int
A> LONG_MAX +2147483647 // 2^31-1
A> -- maximum value for an object of type unsigned long int
A> ULONG_MAX 4294967295 // 2^32-1
A>
A> According to this information the closest integer data type to the maximum
A> value of a line number given in #line is "long" or "unsigned long".
A>
A> Even if we assume that INT_MAX is bigger that 2^31-1 then specifying
A> "unsigned long" in that structure (without changing the order of its fields)
A> will not change its size on i386 and amd64.
Yes, my error was that I looked into INT_MAX on my machine, not in standard.
Thanks again.
--
Totus tuus, Glebius.
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