snprintf_s.c File Reference

#include "safe_str_lib.h"

Include dependency graph for snprintf_s.c:

Functions
EXPORT int	snprintf_s (char *restrict dest, rsize_t dmax, const char *restrict fmt,...)
	The truncating snprintf_s function composes a string with same test that would be printed if format was used on printf. More...

Function Documentation

snprintf_s()

EXPORT int snprintf_s	(	char *restrict	dest,
		rsize_t	dmax,
		const char *restrict	fmt,
			...
	)

The truncating snprintf_s function composes a string with same test that would be printed if format was used on printf.

Instead of being printed, the content is stored in dest. More than dmax - 1 characters might be written, so this variant is unsafe! Always use sprintf_s instead. The resulting character string will be terminated with a null character, unless dmax is zero. If dmax is zero, nothing is written and dest may be a null pointer, however the return value (number of bytes that would be written) is still calculated and returned. Warning: Unlike the safe variant sprintf_s, snprintf_s does not guarantee that the buffer will be null-terminated unless the buffer size is zero.

Note

POSIX specifies that errno is set on error. However, the safeclib extended ES* errors do not set errno, only when the underlying system vsnprintf call fails, errno is set.

Remarks

SPECIFIED IN

• C11 standard (ISO/IEC 9899:2011): K.3.5.3.6 The snprintf_s function (p: 594-595) http://en.cppreference.com/w/c/io/fprintf
• only included in safeclib with –enable-unsafe

Parameters

[out]	dest	pointer to string that will be written into.
[in]	dmax	restricted maximum length of dest
[in]	fmt	format-control string.
[in]	...	optional arguments

Precondition

Neither dest nor fmt shall be a null pointer.

dmax shall not be greater than RSIZE_MAX_STR.

dmax shall not equal zero.

dmax shall be greater than strnlen_s(dest, dmax).

fmt shall not contain the conversion specifier n.

None of the arguments corresponding to s is a null pointer. (not yet)

No encoding error shall occur.

Returns

Number of characters not including the terminating null character (which is always written as long as buffer is not a null pointer and dmax is not zero and not greater than RSIZE_MAX_STR), which would have been written to dest if dmax was ignored, or a negative value if a runtime constraints violation or an encoding error occurred.

Return values

-ESNULLP	when dest/fmt is NULL pointer
-ESZEROL	when dmax = 0
-ESLEMAX	when dmax > RSIZE_MAX_STR
-EINVAL	when fmt contains n

See also

sprintf_s(), vsnprintf_s()