圣经诗篇150篇歌曲:语句不懂

sprintf(qq,"%-12.12f",numb)最终调用的是vsnprintf
调用形式为：
vsnprintf(qq,0xFFFFFFFFUL,"%-12.12f",arg)
其中的arg是一个参数列表，里面包含了所有的参数，因为sprintf有可能有不确定的多个参数。现在这种情况下arg中只有numb一个。

参考linux 2.4.20中vsnprintf的实现为：
int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
{
int len;
unsigned long long num;
int i, base;
char *str, *end, c;
const 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 */
/* 'z' support added 23/7/1999 S.H. */
/* 'z' changed to 'Z' --davidm 1/25/99 */

str = buf;
end = buf + size - 1;

if (end < buf - 1) {
end = ((void *) -1);
size = end - buf + 1;
}

for (; *fmt ; ++fmt) {
if (*fmt != '%') {
if (str <= end)
*str = *fmt;
++str;
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 (isdigit(*fmt))
field_width = skip_atoi(&fmt);
else if (*fmt == '*') {
++fmt;
/* it's the next argument */
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 (isdigit(*fmt))
precision = skip_atoi(&fmt);
else if (*fmt == '*') {
++fmt;
/* it's the next argument */
precision = va_arg(args, int);
}
if (precision < 0)
precision = 0;
}

/* get the conversion qualifier */
qualifier = -1;
if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' || *fmt =='Z') {
qualifier = *fmt;
++fmt;
if (qualifier == 'l' && *fmt == 'l') {
qualifier = 'L';
++fmt;
}
}

/* default base */
base = 10;

switch (*fmt) {
case 'c':
if (!(flags & LEFT)) {
while (--field_width > 0) {
if (str <= end)
*str = ' ';
++str;
}
}
c = (unsigned char) va_arg(args, int);
if (str <= end)
*str = c;
++str;
while (--field_width > 0) {
if (str <= end)
*str = ' ';
++str;
}
continue;

case 's':
s = va_arg(args, char *);
if (!s)
s = "<NULL>";

len = strnlen(s, precision);

if (!(flags & LEFT)) {
while (len < field_width--) {
if (str <= end)
*str = ' ';
++str;
}
}
for (i = 0; i < len; ++i) {
if (str <= end)
*str = *s;
++str; ++s;
}
while (len < field_width--) {
if (str <= end)
*str = ' ';
++str;
}
continue;

case 'p':
if (field_width == -1) {
field_width = 2*sizeof(void *);
flags |= ZEROPAD;
}
str = number(str, end,
(unsigned long) va_arg(args, void *),
16, field_width, precision, flags);
continue;

case 'n':
/* FIXME:
* What does C99 say about the overflow case here? */
if (qualifier == 'l') {
long * ip = va_arg(args, long *);
*ip = (str - buf);
} else if (qualifier == 'Z') {
size_t * ip = va_arg(args, size_t *);
*ip = (str - buf);
} else {
int * ip = va_arg(args, int *);
*ip = (str - buf);
}
continue;

case '%':
if (str <= end)
*str = '%';
++str;
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;

default:
if (str <= end)
*str = '%';
++str;
if (*fmt) {
if (str <= end)
*str = *fmt;
++str;
} else {
--fmt;
}
continue;
}
if (qualifier == 'L')
num = va_arg(args, long long);
else if (qualifier == 'l') {
num = va_arg(args, unsigned long);
if (flags & SIGN)
num = (signed long) num;
} else if (qualifier == 'Z') {
num = va_arg(args, size_t);
} else if (qualifier == 'h') {
num = (unsigned short) va_arg(args, int);
if (flags & SIGN)
num = (signed short) num;
} else {
num = va_arg(args, unsigned int);
if (flags & SIGN)
num = (signed int) num;
}
str = number(str, end, num, base,
field_width, precision, flags);
}
if (str <= end)
*str = '\0';
else if (size > 0)
/* don't write out a null byte if the buf size is zero */
*end = '\0';
/* the trailing null byte doesn't count towards the total
* ++str;
*/
return str-buf;
}

所以实际返回值应该是实际赋值的长度，至少在LINUX中是如此

C语言里的吧？

hehe.. 将打印成功与否true or false返回给i