Date: Mon, 29 Jun 2020 13:30:00 -0700 From: Ravi Pokala <rpokala@freebsd.org> To: Warner Losh <imp@bsdimp.com>, Ravi Pokala <rpokala@freebsd.org> Cc: Hans Petter Selasky <hselasky@freebsd.org>, src-committers <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, <svn-src-head@freebsd.org> Subject: Re: svn commit: r362781 - head/sys/compat/linuxkpi/common/include/linux Message-ID: <D3E3E5CC-6A92-40AB-BDF3-4752C7958435@panasas.com> In-Reply-To: <CANCZdfob=Ri%2B1v1QPg-m9O_%2BqXjD88NcjFQtdSkjGh%2B3GG5SZw@mail.gmail.com> References: <202006291308.05TD8eTP014019@repo.freebsd.org> <E675DB44-963F-498A-97D4-DC326DB3A0EA@panasas.com> <CANCZdfob=Ri%2B1v1QPg-m9O_%2BqXjD88NcjFQtdSkjGh%2B3GG5SZw@mail.gmail.com>
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From: <owner-src-committers@freebsd.org> on behalf of Warner Losh <imp@bsdimp.com>
Date: 2020-06-29, Monday at 13:26
To: Ravi Pokala <rpokala@freebsd.org>
Cc: Hans Petter Selasky <hselasky@freebsd.org>, src-committers <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, <svn-src-head@freebsd.org>
Subject: Re: svn commit: r362781 - head/sys/compat/linuxkpi/common/include/linux
On Mon, Jun 29, 2020, 2:15 PM Ravi Pokala <rpokala@freebsd.org> wrote:
-----Original Message-----
From: <owner-src-committers@freebsd.org> on behalf of Hans Petter Selasky <hselasky@FreeBSD.org>
Date: 2020-06-29, Monday at 06:08
To: <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, <svn-src-head@freebsd.org>
Subject: svn commit: r362781 - head/sys/compat/linuxkpi/common/include/linux
Author: hselasky
Date: Mon Jun 29 13:08:40 2020
New Revision: 362781
URL: https://svnweb.freebsd.org/changeset/base/362781
Log:
Implement is_signed(), type_max() and type_min() function macros in the
LinuxKPI.
MFC after: 1 week
Sponsored by: Mellanox Technologies
Modified:
head/sys/compat/linuxkpi/common/include/linux/kernel.h
Modified: head/sys/compat/linuxkpi/common/include/linux/kernel.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/kernel.h Mon Jun 29 12:59:09 2020 (r362780)
+++ head/sys/compat/linuxkpi/common/include/linux/kernel.h Mon Jun 29 13:08:40 2020 (r362781)
@@ -564,4 +564,20 @@ linux_ratelimited(linux_ratelimit_t *rl)
#define __is_constexpr(x) \
__builtin_constant_p(x)
Hi Hans,
+#define is_signed(x) (((x)-1 / (x)2) == (x)0)
It took me several reads to understand this, until I figured out that 'x' is not a variable, it's the name of a *type*.
If 'x' is a variable, then '(x)-1' is subtraction, but '(x)2' and '(x)0' are nonsensical.
If 'x' is a *type*, then '(x)-1' is typecasting '-1', and similarly for '(x)2' and '(x)0'.
So, perhaps a comment, or a better name for 'x'?
I had similar thoughts. Maybe 't' instead?
Letters are cheap now, Warner; we can afford to spell out "type". :-)
-Ravi (rpokala@)
Warner
Thanks,
Ravi (rpokala@)
+#define type_max(x) ( \
+ (sizeof(x) >= 8) ? (is_signed(x) ? INT64_MAX : UINT64_MAX) : \
+ (sizeof(x) >= 4) ? (is_signed(x) ? INT32_MAX : UINT32_MAX) : \
+ (sizeof(x) >= 2) ? (is_signed(x) ? INT16_MAX : UINT16_MAX) : \
+ (is_signed(x) ? INT8_MAX : UINT8_MAX) \
+)
+
+#define type_min(x) ( \
+ (sizeof(x) >= 8) ? (is_signed(x) ? INT64_MIN : 0) : \
+ (sizeof(x) >= 4) ? (is_signed(x) ? INT32_MIN : 0) : \
+ (sizeof(x) >= 2) ? (is_signed(x) ? INT16_MIN : 0) : \
+ (is_signed(x) ? INT8_MIN : 0) \
+)
+
#endif /* _LINUX_KERNEL_H_ */
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