diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2017-11-23 15:56:38 +0000 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2017-11-24 13:23:36 +0000 |
| commit | e7b47c22e2df14d55e3e4426688c929bf8e3f7fb (patch) | |
| tree | 86c5eb9a8a3e1a6c93b066685c3db3a96e620927 | |
| parent | 79283dda3021316aa6b552086ec6a4aaa3b3b329 (diff) | |
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
| -rw-r--r-- | include/qemu/osdep.h | 29 |
1 files changed, 28 insertions, 1 deletions
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. */ |