[Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types

[Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types

[Peter Maydell]

In our various supported host OSes, the time_t type may be either 32
or 64 bit, and could in theory also be either signed or unsigned.
Notably, in OpenBSD time_t is a 64 bit type even if 'long' is 32
bits, so using LONG_MAX for TIME_MAX is incorrect.

Use an approach suggested by Paolo Bonzini which calculates
the maximum value of the type rather than hardcoding it;
to do this we use the TYPE_MAXIMUM macro from Gnulib.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 include/qemu/osdep.h | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 281782d..e8568a0 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -147,8 +147,35 @@ extern int daemon(int, int);
 #if !defined(ESHUTDOWN)
 #define ESHUTDOWN 4099
 #endif
+
+/* time_t may be either 32 or 64 bits depending on the host OS, and
+ * can be either signed or unsigned, so we can't just hardcode a
+ * specific maximum value. This is not a C preprocessor constant,
+ * so you can't use TIME_MAX in an #ifdef, but for our purposes
+ * this isn't a problem.
+ */
+
+/* The macros TYPE_SIGNED, TYPE_WIDTH, and TYPE_MAXIMUM are from
+ * Gnulib, and are under the LGPL v2.1 or (at your option) any
+ * later version.
+ */
+
+/* True if the real type T is signed.  */
+#define TYPE_SIGNED(t) (!((t)0 < (t)-1))
+
+/* The width in bits of the integer type or expression T.
+ * Padding bits are not supported.
+ */
+#define TYPE_WIDTH(t) (sizeof(t) * CHAR_BIT)
+
+/* The maximum and minimum values for the integer type T.  */
+#define TYPE_MAXIMUM(t)                                                \
+  ((t) (!TYPE_SIGNED(t)                                                \
+        ? (t)-1                                                        \
+        : ((((t)1 << (TYPE_WIDTH(t) - 2)) - 1) * 2 + 1)))
+
 #ifndef TIME_MAX
-#define TIME_MAX LONG_MAX
+#define TIME_MAX TYPE_MAXIMUM(time_t)
 #endif
 
 /* HOST_LONG_BITS is the size of a native pointer in bits. */
-- 
2.7.4

Re: [Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types

[no-reply]

Hi,

This series seems to have some coding style problems. See output below for
more information:

Subject: [Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types
Type: series
Message-id: 1511452598-6077-1-git-send-email-peter.maydell@linaro.org

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

git config --local diff.renamelimit 0
git config --local diff.renames True

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
 * [new tag]               patchew/1511452598-6077-1-git-send-email-peter.maydell@linaro.org -> patchew/1511452598-6077-1-git-send-email-peter.maydell@linaro.org
Switched to a new branch 'test'
1fc46e38d0 osdep.h: Make TIME_MAX handle different time_t types

=== OUTPUT BEGIN ===
Checking PATCH 1/1: osdep.h: Make TIME_MAX handle different time_t types...
ERROR: spaces required around that '-' (ctx:VxV)
#41: FILE: include/qemu/osdep.h:164:
+#define TYPE_SIGNED(t) (!((t)0 < (t)-1))
                                     ^

ERROR: spaces required around that '-' (ctx:VxV)
#51: FILE: include/qemu/osdep.h:174:
+        ? (t)-1                                                        \
              ^

total: 2 errors, 0 warnings, 36 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

=== OUTPUT END ===

Test command exited with code: 1


---
Email generated automatically by Patchew [http://patchew.org/].
Please send your feedback to patchew-devel@freelists.org

Re: [Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types

[Paolo Bonzini]

On 23/11/2017 16:56, Peter Maydell wrote:
> In our various supported host OSes, the time_t type may be either 32
> or 64 bit, and could in theory also be either signed or unsigned.
> Notably, in OpenBSD time_t is a 64 bit type even if 'long' is 32
> bits, so using LONG_MAX for TIME_MAX is incorrect.
> 
> Use an approach suggested by Paolo Bonzini which calculates
> the maximum value of the type rather than hardcoding it;
> to do this we use the TYPE_MAXIMUM macro from Gnulib.
> 
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/qemu/osdep.h | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 281782d..e8568a0 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -147,8 +147,35 @@ extern int daemon(int, int);
>  #if !defined(ESHUTDOWN)
>  #define ESHUTDOWN 4099
>  #endif
> +
> +/* time_t may be either 32 or 64 bits depending on the host OS, and
> + * can be either signed or unsigned, so we can't just hardcode a
> + * specific maximum value. This is not a C preprocessor constant,
> + * so you can't use TIME_MAX in an #ifdef, but for our purposes
> + * this isn't a problem.
> + */
> +
> +/* The macros TYPE_SIGNED, TYPE_WIDTH, and TYPE_MAXIMUM are from
> + * Gnulib, and are under the LGPL v2.1 or (at your option) any
> + * later version.
> + */
> +
> +/* True if the real type T is signed.  */
> +#define TYPE_SIGNED(t) (!((t)0 < (t)-1))
> +
> +/* The width in bits of the integer type or expression T.
> + * Padding bits are not supported.
> + */
> +#define TYPE_WIDTH(t) (sizeof(t) * CHAR_BIT)
> +
> +/* The maximum and minimum values for the integer type T.  */
> +#define TYPE_MAXIMUM(t)                                                \
> +  ((t) (!TYPE_SIGNED(t)                                                \
> +        ? (t)-1                                                        \
> +        : ((((t)1 << (TYPE_WIDTH(t) - 2)) - 1) * 2 + 1)))
> +
>  #ifndef TIME_MAX
> -#define TIME_MAX LONG_MAX
> +#define TIME_MAX TYPE_MAXIMUM(time_t)
>  #endif
>  
>  /* HOST_LONG_BITS is the size of a native pointer in bits. */
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Re: [Qemu-devel] [PATCH for-2.11?] osdep.h: Make TIME_MAX handle different time_t types

[Peter Maydell]

On 23 November 2017 at 16:00, Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 23/11/2017 16:56, Peter Maydell wrote:
>> In our various supported host OSes, the time_t type may be either 32
>> or 64 bit, and could in theory also be either signed or unsigned.
>> Notably, in OpenBSD time_t is a 64 bit type even if 'long' is 32
>> bits, so using LONG_MAX for TIME_MAX is incorrect.
>>
>> Use an approach suggested by Paolo Bonzini which calculates
>> the maximum value of the type rather than hardcoding it;
>> to do this we use the TYPE_MAXIMUM macro from Gnulib.
>>
>> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---

> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks; applied to master.

-- PMM