snprintf and Visual Studio 2010

Short story: Microsoft has finally implemented snprintf in Visual Studio 2015. On earlier versions you can simulate it as below.

Long version:

Here is the expected behavior for snprintf:

int snprintf( char* buffer, std::size_t buf_size, const char* format, ... );

Writes at most buf_size - 1 characters to a buffer. The resulting character string will be terminated with a null character, unless buf_size is zero. If buf_size is zero, nothing is written and buffer may be a null pointer. The return value is the number of characters that would have been written assuming unlimited buf_size, not counting the terminating null character.

Releases prior to Visual Studio 2015 didn't have a conformant implementation. There are instead non-standard extensions such as _snprintf() (which doesn't write null-terminator on overflow) and _snprintf_s() (which can enforce null-termination, but returns -1 on overflow instead of the number of characters that would have been written).

Suggested fallback for VS 2005 and up:

#if defined(_MSC_VER) && _MSC_VER < 1900#define snprintf c99_snprintf#define vsnprintf c99_vsnprintf__inline int c99_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap){    int count = -1;    if (size != 0)        count = _vsnprintf_s(outBuf, size, _TRUNCATE, format, ap);    if (count == -1)        count = _vscprintf(format, ap);    return count;}__inline int c99_snprintf(char *outBuf, size_t size, const char *format, ...){    int count;    va_list ap;    va_start(ap, format);    count = c99_vsnprintf(outBuf, size, format, ap);    va_end(ap);    return count;}#endif

snprintf is not part of C89. It's standard only in C99. Microsoft has no plan supporting C99.

(But it's also standard in C++0x...!)

See other answers below for a workaround.

If you don't need the return value, you could also just define snprintf as _snprintf_s

#define snprintf(buf,len, format,...) _snprintf_s(buf, len,len, format, __VA_ARGS__)