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 <pbonz...@redhat.com> > Signed-off-by: Peter Maydell <peter.mayd...@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 <pbonz...@redhat.com>
