From e7b47c22e2df14d55e3e4426688c929bf8e3f7fb Mon Sep 17 00:00:00 2001 From: Peter Maydell <peter.maydell@linaro.org> Date: Thu, 23 Nov 2017 15:56:38 +0000 Subject: [PATCH] osdep.h: Make TIME_MAX handle different time_t types 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> Message-id: 1511452598-6077-1-git-send-email-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 281782d526..e8568a0a54 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. */ -- 2.30.2