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
