Linux and Windows snprintf differentiate __linux

Today, when you use the snprintf function, you think:
strcpy, strncpy
strcmp, strncmp
Strcat, Strncat
sprintf, snprintf

Most like to use is snprintf, because it will automatically add '/0 ' in the back. Read it on the Internet. The original VC _snprintf is not like this.

VC in the _SNPRINTF function does not follow this rule, it is not large enough output buffer will not output the end of the '/0 ' (similar to the behavior of the strncpy). So to make the above program work properly, you must make the appropriate changes.

Char buf[5];
_snprintf (BUF, 5, "This is a test string."); BUF becomes "This" and buf[4] is '
BUF[4] = 0; BUF[4] is '/0 ' now. To be safe, manually add the
　　
_snprintf (buf, 6, "This is a test string."); Error:buffer Overflow
_snprintf (BUF, 5, "abc"); BUF becomes "ABC", the value of buf[3] is '/0 ', buf[4] is undefined.

If you want to ensure portability, you have to follow the VC's writing, do one for the standard is very superfluous "fill 0" operation, and then through the definition of a macro to distinguish between the platform selected snprintf or _snprintf.

A small test code:
You can see that there are two different places:
1>. End of '/0 ' processing.
2>. function return value is not the same.

# include < stdio. H>
# include < string. H>

# define Str_len 32

# ifdef _WIN32
# define SNPRINTF _snprintf
# endif

/**
* Dump string
*/
static void Dump_str (const char * title, const char * str, int len)
{
int i;

printf ("%s[%d].%p/n", title, Len, str);
for (i = 0; i < len; i+ +)
printf ("<%c,%02x>", str[i], (unsigned char) str[i]);

printf ("n");
}

int main (int argc, char * * argv)
{
int t;
Char str1[Str_len], str2[Str_len];

strcpy (str1, "123456789");
Dump_str ("str1", str1, Str_len);

t = snprintf (str2, Str_len, "%s", str1);
Dump_str ("str2", str2, Str_len);
printf ("snprintf () ret.%d/n", t);

t = snprintf (STR2, 5, "%s", str1);
Dump_str ("str2", str2, Str_len);
printf ("snprintf () ret.%d/n", t);

return (0);
}

/*
Test ENV:
GCC version 3.4.5 20051201 (Red Hat 3.4.5-2)

Result:
str1[32].0xbffb9190
<1,31><2,32><3,33><4,34><5,35><6,36><7,37><8,38><9,39> <,00><?fb><?bf><?d5><?82><,04><,08><,00><,00><,00> <,00><,00><,00><,00><, 00><?c8><?91><?fb><?bf><& 26><?85><,04><,08>
str2[32].0xbffb9170
<1,31><2,32><3,33><4,34><5,35><6,36><7,37><8,38><9,39> <,00><w,77><,01><, 00><?92><?fb><?bf><?f8><d,64><?ad ><,00><,00><,00><,00><,00><,00><,00><,00><,00><, 00 ><,00><,00><,00>
snprintf () ret.9
str2[32].0xbffb9170
<1,31><2,32><3,33><4,34><,00><6,36><7,37><8,38><9,39> <,00><w,77><,01><, 00><?92><?fb><?bf><?f8><d,64><?ad ><,00><,00><,00><,00><,00><,00><,00><,00><,00><, 00 ><,00><,00><,00>
snprintf () ret.9

-------------------------------------------------------------------------
Test ENV:
Microsoft Windows XP [version 5.1.2600]
Microsoft (R) 32-bit/C + + optimizing Compiler Version 12.00.8168 for 80x86


Result:
Str1[32].0012ff60
<1,31><2,32><3,33><4,34><5,35><6,36><7,37><8,38><9,39> <,00><,12><,00><,10><,1d><@,40><,00><,00><,08><, 00 ><,00><,04><,00><,00><,00><,00><,00><,00><, 00&GT;&LT;?E0 ><,1e><@,40><,00>
str2[32].0012ff3c
<1,31><2,32><3,33><4,34><5,35><6,36><7,37><8,38><9,39> <,00><?93><|,7c><& #63733;,ff><& #63733;,ff><& #63733;,ff>< & #63733;,ff><?eb><,06><?93><|,7c><?ef><0,30><@,40><,00> <,00><,00><7,37><,00><,09><,00><,00><,00>
snprintf () ret.9
str2[32].0012ff3c
<1,31><2,32><3,33><4,34><5,35><6,36><7,37><8,38><9,39> <,00><?93><|,7c><& #63733;,ff><& #63733;,ff><& #63733;,ff>< & #63733;,ff><?eb><,06><?93><|,7c><?ef><0,30><@,40><,00> <,00><,00><7,37><,00><,09><,00><,00><,00>
snprintf () ret.-1
*/

http://blog.csdn.net/locape/article/details/5657378