使用FLT_MIN时为什么输出为0？
# include <stdio.h># include <float.h>
int main(void)
{
printf("%f\n", FLT_MIN);//输出为0
return 0;
}
2015-04-11 13:30
2015-04-11 13:36
程序代码：
/***
*float.h - constants for floating point values
*
* Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
* This file contains defines for a number of implementation dependent
* values which are commonly used by sophisticated numerical (floating
* point) programs.
* [ANSI]
*
* [Public]
*
****/
#pragma once
#ifndef _INC_FLOAT
#define _INC_FLOAT
#include <crtdefs.h>
#include <crtwrn.h>
/* Define _CRT_MANAGED_FP_DEPRECATE */
#ifndef _CRT_MANAGED_FP_DEPRECATE
#ifdef _CRT_MANAGED_FP_NO_DEPRECATE
#define _CRT_MANAGED_FP_DEPRECATE
#else /* _CRT_MANAGED_FP_NO_DEPRECATE */
#if defined (_M_CEE)
#define _CRT_MANAGED_FP_DEPRECATE _CRT_DEPRECATE_TEXT("Direct floating point control is not supported or reliable from within managed code. ")
#else /* defined (_M_CEE) */
#define _CRT_MANAGED_FP_DEPRECATE
#endif /* defined (_M_CEE) */
#endif /* _CRT_MANAGED_FP_NO_DEPRECATE */
#endif /* _CRT_MANAGED_FP_DEPRECATE */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/*
Define the floating point precision used.
For x86, results are in double precision (unless /arch:sse2
is used, in which case results are in source precision).
For x64 and ARM, results are in source precision.
If the compiler is invoked with /fp:fast, the compiler is
allowed to use the fastest precision and even mix within
a single function, so precision is indeterminable.
Note that manipulating the floating point behavior using the
float_control/fenv_access/fp_contract #pragmas may alter the
actual floating point evaluation method, which may in turn
invalidate the value of FLT_EVAL_METHOD.
*/
#if defined(_M_FP_FAST)
#define FLT_EVAL_METHOD -1
#else
#if defined(_M_IX86)
#if _M_IX86_FP == 2
#define FLT_EVAL_METHOD 0
#else
#define FLT_EVAL_METHOD 2
#endif
#else
#define FLT_EVAL_METHOD 0
#endif
#endif
#define DBL_DIG 15 /* # of decimal digits of precision */
#define DBL_EPSILON 2.2204460492503131e-016 /* smallest such that 1.0+DBL_EPSILON != 1.0 */
#define DBL_MANT_DIG 53 /* # of bits in mantissa */
#define DBL_MAX 1.7976931348623158e+308 /* max value */
#define DBL_MAX_10_EXP 308 /* max decimal exponent */
#define DBL_MAX_EXP 1024 /* max binary exponent */
#define DBL_MIN 2.2250738585072014e-308 /* min positive value */
#define DBL_MIN_10_EXP (-307) /* min decimal exponent */
#define DBL_MIN_EXP (-1021) /* min binary exponent */
#define _DBL_RADIX 2 /* exponent radix */
#define _DBL_ROUNDS 1 /* addition rounding: near */
#define FLT_DIG 6 /* # of decimal digits of precision */
#define FLT_EPSILON 1.192092896e-07F /* smallest such that 1.0+FLT_EPSILON != 1.0 */
#define FLT_GUARD 0
#define FLT_MANT_DIG 24 /* # of bits in mantissa */
#define FLT_MAX 3.402823466e+38F /* max value */
#define FLT_MAX_10_EXP 38 /* max decimal exponent */
#define FLT_MAX_EXP 128 /* max binary exponent */
#define FLT_MIN 1.175494351e-38F /* min positive value */
#define FLT_MIN_10_EXP (-37) /* min decimal exponent */
#define FLT_MIN_EXP (-125) /* min binary exponent */
#define FLT_NORMALIZE 0
#define FLT_RADIX 2 /* exponent radix */
#define FLT_ROUNDS 1 /* addition rounding: near */
#define LDBL_DIG DBL_DIG /* # of decimal digits of precision */
#define LDBL_EPSILON DBL_EPSILON /* smallest such that 1.0+LDBL_EPSILON != 1.0 */
#define LDBL_MANT_DIG DBL_MANT_DIG /* # of bits in mantissa */
#define LDBL_MAX DBL_MAX /* max value */
#define LDBL_MAX_10_EXP DBL_MAX_10_EXP /* max decimal exponent */
#define LDBL_MAX_EXP DBL_MAX_EXP /* max binary exponent */
#define LDBL_MIN DBL_MIN /* min positive value */
#define LDBL_MIN_10_EXP DBL_MIN_10_EXP /* min decimal exponent */
#define LDBL_MIN_EXP DBL_MIN_EXP /* min binary exponent */
#define _LDBL_RADIX DBL_RADIX /* exponent radix */
#define _LDBL_ROUNDS DBL_ROUNDS /* addition rounding: near */
#define DECIMAL_DIG 10 /* float rounded to decimal and back */
/* Function prototypes */
/* Reading or writing the floating point control/status words is not supported in managed code */
_CRT_MANAGED_FP_DEPRECATE _CRTIMP unsigned int __cdecl _clearfp(void);
#pragma warning(push)
#pragma warning(disable: 4141)
_CRT_MANAGED_FP_DEPRECATE _CRT_INSECURE_DEPRECATE(_controlfp_s) _CRTIMP unsigned int __cdecl _controlfp(_In_ unsigned int _NewValue,_In_ unsigned int _Mask);
#pragma warning(pop)
_CRT_MANAGED_FP_DEPRECATE _CRTIMP void __cdecl _set_controlfp(_In_ unsigned int _NewValue, _In_ unsigned int _Mask);
_CRT_MANAGED_FP_DEPRECATE _CRTIMP errno_t __cdecl _controlfp_s(_Out_opt_ unsigned int *_CurrentState, _In_ unsigned int _NewValue, _In_ unsigned int _Mask);
_CRT_MANAGED_FP_DEPRECATE _CRTIMP unsigned int __cdecl _statusfp(void);
_CRT_MANAGED_FP_DEPRECATE _CRTIMP void __cdecl _fpreset(void);
#if defined (_M_IX86)
_CRT_MANAGED_FP_DEPRECATE _CRTIMP void __cdecl _statusfp2(_Out_opt_ unsigned int *_X86_status, _Out_opt_ unsigned int *_SSE2_status);
#endif /* defined (_M_IX86) */
#define _clear87 _clearfp
#define _status87 _statusfp
/*
* Abstract User Status Word bit definitions
*/
#define _SW_INEXACT 0x00000001 /* inexact (precision) */
#define _SW_UNDERFLOW 0x00000002 /* underflow */
#define _SW_OVERFLOW 0x00000004 /* overflow */
#define _SW_ZERODIVIDE 0x00000008 /* zero divide */
#define _SW_INVALID 0x00000010 /* invalid */
#define _SW_DENORMAL 0x00080000 /* denormal status bit */
/*
* New Control Bit that specifies the ambiguity in control word.
*/
#define _EM_AMBIGUIOUS 0x80000000 /* for backwards compatibility old spelling */
#define _EM_AMBIGUOUS 0x80000000
/*
* Abstract User Control Word Mask and bit definitions
*/
#define _MCW_EM 0x0008001f /* interrupt Exception Masks */
#define _EM_INEXACT 0x00000001 /* inexact (precision) */
#define _EM_UNDERFLOW 0x00000002 /* underflow */
#define _EM_OVERFLOW 0x00000004 /* overflow */
#define _EM_ZERODIVIDE 0x00000008 /* zero divide */
#define _EM_INVALID 0x00000010 /* invalid */
#define _EM_DENORMAL 0x00080000 /* denormal exception mask (_control87 only) */
#define _MCW_RC 0x00000300 /* Rounding Control */
#define _RC_NEAR 0x00000000 /* near */
#define _RC_DOWN 0x00000100 /* down */
#define _RC_UP 0x00000200 /* up */
#define _RC_CHOP 0x00000300 /* chop */
/*
* i386 specific definitions
*/
#define _MCW_PC 0x00030000 /* Precision Control */
#define _PC_64 0x00000000 /* 64 bits */
#define _PC_53 0x00010000 /* 53 bits */
#define _PC_24 0x00020000 /* 24 bits */
#define _MCW_IC 0x00040000 /* Infinity Control */
#define _IC_AFFINE 0x00040000 /* affine */
#define _IC_PROJECTIVE 0x00000000 /* projective */
/*
* RISC specific definitions
*/
#define _MCW_DN 0x03000000 /* Denormal Control */
#define _DN_SAVE 0x00000000 /* save denormal results and operands */
#define _DN_FLUSH 0x01000000 /* flush denormal results and operands to zero */
#define _DN_FLUSH_OPERANDS_SAVE_RESULTS 0x02000000 /* flush operands to zero and save results */
#define _DN_SAVE_OPERANDS_FLUSH_RESULTS 0x03000000 /* save operands and flush results to zero */
/* initial Control Word value */
#if defined (_M_IX86)
#define _CW_DEFAULT ( _RC_NEAR + _PC_53 + _EM_INVALID + _EM_ZERODIVIDE + _EM_OVERFLOW + _EM_UNDERFLOW + _EM_INEXACT + _EM_DENORMAL)
#elif defined (_M_X64) || defined (_M_ARM)
#define _CW_DEFAULT ( _RC_NEAR + _EM_INVALID + _EM_ZERODIVIDE + _EM_OVERFLOW + _EM_UNDERFLOW + _EM_INEXACT + _EM_DENORMAL)
#endif /* defined (_M_X64) || defined (_M_ARM) */
_CRT_MANAGED_FP_DEPRECATE _CRTIMP unsigned int __cdecl _control87(_In_ unsigned int _NewValue,_In_ unsigned int _Mask);
#if defined (_M_IX86)
_CRT_MANAGED_FP_DEPRECATE _CRTIMP int __cdecl __control87_2(_In_ unsigned int _NewValue, _In_ unsigned int _Mask,
_Out_opt_ unsigned int* _X86_cw, _Out_opt_ unsigned int* _Sse2_cw);
#endif /* defined (_M_IX86) */
/* Global variable holding floating point error code */
_Check_return_ _CRTIMP extern int * __cdecl __fpecode(void);
#define _fpecode (*__fpecode())
/* invalid subconditions (_SW_INVALID also set) */
#define _SW_UNEMULATED 0x0040 /* unemulated instruction */
#define _SW_SQRTNEG 0x0080 /* square root of a neg number */
#define _SW_STACKOVERFLOW 0x0200 /* FP stack overflow */
#define _SW_STACKUNDERFLOW 0x0400 /* FP stack underflow */
/* Floating point error signals and return codes */
#define _FPE_INVALID 0x81
#define _FPE_DENORMAL 0x82
#define _FPE_ZERODIVIDE 0x83
#define _FPE_OVERFLOW 0x84
#define _FPE_UNDERFLOW 0x85
#define _FPE_INEXACT 0x86
#define _FPE_UNEMULATED 0x87
#define _FPE_SQRTNEG 0x88
#define _FPE_STACKOVERFLOW 0x8a
#define _FPE_STACKUNDERFLOW 0x8b
#define _FPE_EXPLICITGEN 0x8c /* raise( SIGFPE ); */
#define _FPE_MULTIPLE_TRAPS 0x8d /* on x86 with arch:SSE2 OS returns these exceptions */
#define _FPE_MULTIPLE_FAULTS 0x8e
/* IEEE recommended functions */
_Check_return_ _CRTIMP double __cdecl _copysign(_In_ double _Number, _In_ double _Sign);
_Check_return_ _CRTIMP double __cdecl _chgsign(_In_ double _X);
_Check_return_ _CRTIMP double __cdecl _scalb(_In_ double _X, _In_ long _Y);
_Check_return_ _CRTIMP double __cdecl _logb(_In_ double _X);
_Check_return_ _CRTIMP double __cdecl _nextafter(_In_ double _X, _In_ double _Y);
_Check_return_ _CRTIMP int __cdecl _finite(_In_ double _X);
_Check_return_ _CRTIMP int __cdecl _isnan(_In_ double _X);
_Check_return_ _CRTIMP int __cdecl _fpclass(_In_ double _X);
#ifdef _M_X64
_Check_return_ _CRTIMP float __cdecl _scalbf(_In_ float _X, _In_ long _Y);
#endif /* _M_X64 */
#define _FPCLASS_SNAN 0x0001 /* signaling NaN */
#define _FPCLASS_QNAN 0x0002 /* quiet NaN */
#define _FPCLASS_NINF 0x0004 /* negative infinity */
#define _FPCLASS_NN 0x0008 /* negative normal */
#define _FPCLASS_ND 0x0010 /* negative denormal */
#define _FPCLASS_NZ 0x0020 /* -0 */
#define _FPCLASS_PZ 0x0040 /* +0 */
#define _FPCLASS_PD 0x0080 /* positive denormal */
#define _FPCLASS_PN 0x0100 /* positive normal */
#define _FPCLASS_PINF 0x0200 /* positive infinity */
#if !__STDC__
/* Non-ANSI names for compatibility */
#define clear87 _clear87
#define status87 _status87
#define control87 _control87
_CRT_MANAGED_FP_DEPRECATE _CRTIMP void __cdecl fpreset(void);
#define DBL_RADIX _DBL_RADIX
#define DBL_ROUNDS _DBL_ROUNDS
#define LDBL_RADIX _LDBL_RADIX
#define LDBL_ROUNDS _LDBL_ROUNDS
#define EM_AMBIGUIOUS _EM_AMBIGUOUS /* for backwards compatibility old spelling */
#define EM_AMBIGUOUS _EM_AMBIGUOUS
#define MCW_EM _MCW_EM
#define EM_INVALID _EM_INVALID
#define EM_DENORMAL _EM_DENORMAL
#define EM_ZERODIVIDE _EM_ZERODIVIDE
#define EM_OVERFLOW _EM_OVERFLOW
#define EM_UNDERFLOW _EM_UNDERFLOW
#define EM_INEXACT _EM_INEXACT
#define MCW_IC _MCW_IC
#define IC_AFFINE _IC_AFFINE
#define IC_PROJECTIVE _IC_PROJECTIVE
#define MCW_RC _MCW_RC
#define RC_CHOP _RC_CHOP
#define RC_UP _RC_UP
#define RC_DOWN _RC_DOWN
#define RC_NEAR _RC_NEAR
#define MCW_PC _MCW_PC
#define PC_24 _PC_24
#define PC_53 _PC_53
#define PC_64 _PC_64
#define CW_DEFAULT _CW_DEFAULT
#define SW_INVALID _SW_INVALID
#define SW_DENORMAL _SW_DENORMAL
#define SW_ZERODIVIDE _SW_ZERODIVIDE
#define SW_OVERFLOW _SW_OVERFLOW
#define SW_UNDERFLOW _SW_UNDERFLOW
#define SW_INEXACT _SW_INEXACT
#define SW_UNEMULATED _SW_UNEMULATED
#define SW_SQRTNEG _SW_SQRTNEG
#define SW_STACKOVERFLOW _SW_STACKOVERFLOW
#define SW_STACKUNDERFLOW _SW_STACKUNDERFLOW
#define FPE_INVALID _FPE_INVALID
#define FPE_DENORMAL _FPE_DENORMAL
#define FPE_ZERODIVIDE _FPE_ZERODIVIDE
#define FPE_OVERFLOW _FPE_OVERFLOW
#define FPE_UNDERFLOW _FPE_UNDERFLOW
#define FPE_INEXACT _FPE_INEXACT
#define FPE_UNEMULATED _FPE_UNEMULATED
#define FPE_SQRTNEG _FPE_SQRTNEG
#define FPE_STACKOVERFLOW _FPE_STACKOVERFLOW
#define FPE_STACKUNDERFLOW _FPE_STACKUNDERFLOW
#define FPE_EXPLICITGEN _FPE_EXPLICITGEN
#endif /* !__STDC__ */
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* _INC_FLOAT */
2015-04-11 13:38
2015-04-11 13:56