经过查看，发现应该是以下的问题(编译器：DEV－C++ 4.9.9.2)
printf的定义中，将以上的参数转为字符串时出错。
源代码如下：
/*******************************************************
int vsprintf(char *buf, const char *fmt, va_list args)
{
int len;
unsigned long num;
int i, base;
char *str;
char *s;
int flags;
// Flags to number()
int field_width;
// Width of output field
int precision;
// Min. # of digits for integers; max number of chars for from string
int qualifier;
// 'h', 'l', or 'L' for integer fields
for (str = buf; *fmt; fmt++)
{
if (*fmt != '%')
{
*str++ = *fmt;
continue;
}
// Process flags
flags = 0;
repeat:
fmt++; // This also skips first '%'
switch (*fmt)
{
case '-': flags |= LEFT; goto repeat;
case '+': flags |= PLUS; goto repeat;
case ' ': flags |= SPACE; goto repeat;
case '#': flags |= SPECIAL; goto repeat;
case '0': flags |= ZEROPAD; goto repeat;
}
// Get field width
field_width = -1;
if (is_digit(*fmt))
field_width = skip_atoi(&fmt);
else if (*fmt == '*')
{
fmt++;
field_width = va_arg(args, int);
if (field_width
< 0)
{
field_width = -field_width;
flags |= LEFT;
}
}
// Get the precision
precision = -1;
if (*fmt == '.')
{
++fmt;
if (is_digit(*fmt))
precision = skip_atoi(&fmt);
else if (*fmt == '*')
{
++fmt;
precision = va_arg(args, int);
}
if (precision
< 0) precision = 0;
}
// Get the conversion qualifier
qualifier = -1;
if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L')
{
qualifier = *fmt;
fmt++;
}
// Default base
base = 10;
switch (*fmt)
{
case 'c':
if (!(flags & LEFT)) while (--field_width > 0) *str++ = ' ';
*str++ = (unsigned char) va_arg(args, int);
while (--field_width > 0) *str++ = ' ';
continue;
case 's':
s = va_arg(args, char *);
if (!s)
s = " <NULL>";
len = strnlen(s, precision);
if (!(flags & LEFT)) while (len
< field_width--) *str++ = ' ';
for (i = 0; i
< len; ++i) *str++ = *s++;
while (len
< field_width--) *str++ = ' ';
continue;
case 'p':
if (field_width == -1)
{
field_width = 2 * sizeof(void *);
flags |= ZEROPAD;
}
str = number(str, (unsigned long) va_arg(args, void *), 16, field_width, precision, flags);
continue;
case 'n':
if (qualifier == 'l')
{
long *ip = va_arg(args, long *);
*ip = (str - buf);
}
else
{
int *ip = va_arg(args, int *);
*ip = (str - buf);
}
continue;
case 'A':
flags |= LARGE;
case 'a':
if (qualifier == 'l')
str = eaddr(str, va_arg(args, unsigned char *), field_width, precision, flags);
else
str = iaddr(str, va_arg(args, unsigned char *), field_width, precision, flags);
continue;
// Integer number formats - set up the flags and "break"
case 'o':
base = 8;
break;
case 'X':
flags |= LARGE;
case 'x':
base = 16;
break;
case 'd':
case 'i':
flags |= SIGN;
case 'u':
break;
case 'E':
case 'G':
case 'e':
case 'f':
case 'g':
str = flt(str, va_arg(args, double), field_width, precision, *fmt, flags | SIGN);
continue;
default:
if (*fmt != '%') *str++ = '%';
if (*fmt)
*str++ = *fmt;
else
--fmt;
continue;
}
if (qualifier == 'l')
num = va_arg(args, unsigned long);
else if (qualifier == 'h')
{
if (flags & SIGN)
num = va_arg(args, short);
else
num = va_arg(args, unsigned short);
}
else if (flags & SIGN)
num = va_arg(args, int);
else
num = va_arg(args, unsigned int);
str = number(str, num, base, field_width, precision, flags);
}
*str = '\0';
return str - buf;
}
*************************************************************************/
也就是说，有可能将float型先输出一个unsigned short,后面两个字节又与四字节的float b被输出，但只是六字节中的四个。从而出现这样问题。
所以，如果是这样的话，最后一个变量b将会被正确输出。
printf("%u,%u,%5.3e",a,b);
//%u %u 输出 float a, %5.3e 输出 float b
