Question

我正在使用 Windows 8.1 64位。

IDE： Eclipse Luna（4.4.0）。

并使用 MinGW v4.9.1

我在eclipse中输入了这个程序，但它显示的是在long double中显示零。我尝试了％llf和％Lf，并尝试了类型转换，但没有任何方法可以帮助我。

1.   int main(void) {  
2.   float floatNumber;
3.   double doubleNumber;
4.   long double longDoubleNumber;
5.
6.   // Size of floating point types
7.   printf("Storage size for unsigned float : %lu  bytes \n", sizeof(float));
8.   printf("Storage size for double :         %lu  bytes \n", sizeof(double));
9.   printf("Storage size for long double :   %lu  bytes \n", sizeof(long double));
10.
11.  floatNumber = 2.0/3.0;
12.  doubleNumber = 2.0/3.0;
13.  longDoubleNumber = 2.0/3.0;
14.
15.  puts("\nCompare precision at 4 decimal points:");
16.  printf("floatNumber      = %1.4f\n", floatNumber);
17.  printf("doubleNumber     = %1.4lf\n", doubleNumber);
18.  printf("longDoubleNumber = %1.4Lf\n", longDoubleNumber);
19.
20.  puts("\nCompare precision at 10 decimal points:");
21.  printf("floatNumber      = %1.10f\n", floatNumber);
22.  printf("doubleNumber     = %1.10lf\n", doubleNumber);
23.  printf("longDoubleNumber = %1.10Lf\n", longDoubleNumber);
24.
25.  puts("\nCompare precision at 30 decimal points:");
26.  printf("floatNumber      = %1.30f\n", floatNumber);
27.  printf("doubleNumber     = %1.50lf\n", doubleNumber);
28.  printf("longDoubleNumber = %1.50Lf\n", longDoubleNumber);
29.  return 0;
30.  }

这是输出： -

Floating point type usage in C:
Storage size for unsigned float : 4  bytes 
Storage size for double :         8  bytes 
Storage size for long double :   16  bytes 

Compare precision at 4 decimal points:
floatNumber      = 0.6667
doubleNumber     = 0.6667
longDoubleNumber = 0.0000

Compare precision at 10 decimal points:
floatNumber      = 0.6666666865
doubleNumber     = 0.6666666667
longDoubleNumber = 0.0000000000

Compare precision at 30 decimal points:
floatNumber      = 0.666666686534881590000000000000
doubleNumber     = 0.66666666666666663000000000000000000000000000000000
longDoubleNumber = 0.00000000000000000000000000000000000000000000000000

当我尝试这个时：

printf("Storage size for unsigned float : %zu  bytes \n", sizeof floatNumber);
printf("Storage size for double :         %zu  bytes \n", sizeof doubleNumber);
printf("Storage size for long double :   %zu  bytes \n", sizeof longDoubleNumber);

输出是：

Floating point type usage in C:
Storage size for unsigned float : zu  bytes 
Storage size for double :         zu  bytes 
Storage size for long double :   zu  bytes

其他一切与上述相同。

Eclipse显示的警告列表是： -

line 7,8,9,18,23,28:- too many arguments for format [-Wformat-extra-args]
line 18,23,28:- unknown conversion type character 'L' in format [-Wformat=]
line 7,8,9:- format '%lu' expects argument of type 'long unsigned int', but argument
             2 has type 'long long unsigned int' [-Wformat=]

{if i use %zu instead of %lu}
line 7,8,9:- unknown conversion type character 'z' in format [-Wformat=]

long double的格式说明符是什么？

Answer 1

size_t是类型sizeof()返回，因此请使用zu格式说明符。使用错误的格式说明符会导致未定义的行为。

printf("Storage size for unsigned float : %zu  bytes \n", sizeof(float));

注意：%zd适用于已签名的ssize_t

c中long double的Format Specifier

1 个答案: