| Message ID | 20171106005656.GC84093@humpty.home.comstyle.com |
|---|---|
| State | New |
| Headers | show |
| Series | osdep: Deal with TIME_MAX and OpenBSD 64-bit time_t | expand |
On 6 November 2017 at 00:56, Brad Smith <brad@comstyle.com> wrote: > Define TIME_MAX to LLONG_MAX for OpenBSD since OpenBSD uses 64-bit time_t. > > Signed-off-by: Brad Smith <brad@comstyle.com> > > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index 6855b94bbf..824714049b 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -132,8 +132,12 @@ extern int daemon(int, int); > #define ESHUTDOWN 4099 > #endif > #ifndef TIME_MAX > +#ifdef __OpenBSD__ > +#define TIME_MAX LLONG_MAX > +#else > #define TIME_MAX LONG_MAX > #endif > +#endif I'm not really a fan of adding new OS-specific #ifdefs -- what if one of the other BSDs uses or switches to 64-bit time_t for 32-bit platforms? Is there some way we can detect this generically at compile time (possibly in configure) ? thanks -- PMM
On Mon, Nov 06, 2017 at 10:51:16AM +0000, Peter Maydell wrote: > On 6 November 2017 at 00:56, Brad Smith <brad@comstyle.com> wrote: > > Define TIME_MAX to LLONG_MAX for OpenBSD since OpenBSD uses 64-bit time_t. > > > > Signed-off-by: Brad Smith <brad@comstyle.com> > > > > > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > > index 6855b94bbf..824714049b 100644 > > --- a/include/qemu/osdep.h > > +++ b/include/qemu/osdep.h > > @@ -132,8 +132,12 @@ extern int daemon(int, int); > > #define ESHUTDOWN 4099 > > #endif > > #ifndef TIME_MAX > > +#ifdef __OpenBSD__ > > +#define TIME_MAX LLONG_MAX > > +#else > > #define TIME_MAX LONG_MAX > > #endif > > +#endif > > I'm not really a fan of adding new OS-specific #ifdefs -- > what if one of the other BSDs uses or switches to 64-bit > time_t for 32-bit platforms? Is there some way we can detect > this generically at compile time (possibly in configure) ? You could use a pair of compile time asserts to figure it out. Would need one compile test to check 32 vs 64 bit: #include <time.h> char time_t_64bit[sizeof(time_t) == 8 ? 1 : -1]; and a second to check signed vs unsigned: #include <time.h> char time_t_signed[(time_t) -1 < 0 ? 1 : -1]; Save each of these programs to the file $TMPC, and then run 'compile_object' from configure. You then have a decision matrix for 4 different TIME_MAX values to write into config-host.h. Regards, Daniel
On 06.11.2017 11:51, Peter Maydell wrote: > On 6 November 2017 at 00:56, Brad Smith <brad@comstyle.com> wrote: >> Define TIME_MAX to LLONG_MAX for OpenBSD since OpenBSD uses 64-bit time_t. >> >> Signed-off-by: Brad Smith <brad@comstyle.com> >> >> >> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h >> index 6855b94bbf..824714049b 100644 >> --- a/include/qemu/osdep.h >> +++ b/include/qemu/osdep.h >> @@ -132,8 +132,12 @@ extern int daemon(int, int); >> #define ESHUTDOWN 4099 >> #endif >> #ifndef TIME_MAX >> +#ifdef __OpenBSD__ >> +#define TIME_MAX LLONG_MAX >> +#else >> #define TIME_MAX LONG_MAX >> #endif >> +#endif > > I'm not really a fan of adding new OS-specific #ifdefs -- > what if one of the other BSDs uses or switches to 64-bit > time_t for 32-bit platforms? Is there some way we can detect > this generically at compile time (possibly in configure) ? > NetBSD 32-bit ports switched to 64-bit in 2009. There are no longer supported releases with 32-bit time_t. > thanks > -- PMM >
On 06/11/2017 12:26, Daniel P. Berrange wrote: > On Mon, Nov 06, 2017 at 10:51:16AM +0000, Peter Maydell wrote: >> On 6 November 2017 at 00:56, Brad Smith <brad@comstyle.com> wrote: >>> Define TIME_MAX to LLONG_MAX for OpenBSD since OpenBSD uses 64-bit time_t. >>> >>> Signed-off-by: Brad Smith <brad@comstyle.com> >>> >>> >>> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h >>> index 6855b94bbf..824714049b 100644 >>> --- a/include/qemu/osdep.h >>> +++ b/include/qemu/osdep.h >>> @@ -132,8 +132,12 @@ extern int daemon(int, int); >>> #define ESHUTDOWN 4099 >>> #endif >>> #ifndef TIME_MAX >>> +#ifdef __OpenBSD__ >>> +#define TIME_MAX LLONG_MAX >>> +#else >>> #define TIME_MAX LONG_MAX >>> #endif >>> +#endif >> >> I'm not really a fan of adding new OS-specific #ifdefs -- >> what if one of the other BSDs uses or switches to 64-bit >> time_t for 32-bit platforms? Is there some way we can detect >> this generically at compile time (possibly in configure) ? > > You could use a pair of compile time asserts to figure it out. > > Would need one compile test to check 32 vs 64 bit: > > #include <time.h> > char time_t_64bit[sizeof(time_t) == 8 ? 1 : -1]; > > and a second to check signed vs unsigned: > > #include <time.h> > char time_t_signed[(time_t) -1 < 0 ? 1 : -1]; > > > Save each of these programs to the file $TMPC, and then run 'compile_object' > from configure. You then have a decision matrix for 4 different TIME_MAX > values to write into config-host.h. What about #define type_max(t) \ ((t) -1 > 0 \ ? (t)~0 \ : (((t)1) << \ (sizeof(t) * 8 - 1)) - 1) \ #define TIME_MAX type_max(time_t) ? We don't need it to be a cpp constant, do we? Or if we did, we could assume it to be signed, it's enough for the three users. Thanks, Paolo
On 6 November 2017 at 17:41, Paolo Bonzini <pbonzini@redhat.com> wrote: > What about > > #define type_max(t) \ > ((t) -1 > 0 \ > ? (t)~0 \ > : (((t)1) << \ > (sizeof(t) * 8 - 1)) - 1) \ > > #define TIME_MAX type_max(time_t) > > ? We don't need it to be a cpp constant, do we? Or if we did, we could > assume it to be signed, it's enough for the three users. GCC doesn't like this phrasing, it complains qmp.c: In function ‘qmp_expire_password’: qmp.c:334:89: error: integer overflow in expression [-Werror=overflow] because of the shift into the sign bit. Instead we can borrow the TYPE_MAXIMUM macro from gnulib, which uses basically the same approach but avoids the UB and the compiler warning. I'll send a patch in a bit. thanks -- PMM
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index 6855b94bbf..824714049b 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -132,8 +132,12 @@ extern int daemon(int, int); #define ESHUTDOWN 4099 #endif #ifndef TIME_MAX +#ifdef __OpenBSD__ +#define TIME_MAX LLONG_MAX +#else #define TIME_MAX LONG_MAX #endif +#endif /* HOST_LONG_BITS is the size of a native pointer in bits. */ #if UINTPTR_MAX == UINT32_MAX
Define TIME_MAX to LLONG_MAX for OpenBSD since OpenBSD uses 64-bit time_t. Signed-off-by: Brad Smith <brad@comstyle.com>