_vcprintf_s, _vcprintf_s_l, _vcwprintf_s, _vcwprintf_s_l

Writes formatted output to the console by using a pointer to a list of arguments. These versions of _vcprintf, _vcprintf_l, _vcwprintf, _vcwprintf_l have security enhancements, as described in Security features in the CRT.

Important

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

int _vcprintf_s(
   char const* const format,
   va_list argptr
);
int _vcprintf_s_l(
   char const* const format,
   _locale_t locale,
   va_list argptr
);
int _vcwprintf_s(
   wchar_t const* const format,
   va_list argptr
);
int _vcwprintf_s_l(
   wchar_t const* const format,
   _locale_t locale,
   va_list argptr
);

Parameters

format
Format specification.

argptr
Pointer to the list of arguments.

locale
The locale to use.

For more information, see Format specification syntax: printf and wprintf functions.

Return value

The number of characters written, or a negative value if an output error occurs.

Like the less secure versions of these functions, if format is a null pointer, the invalid parameter handler is invoked, as described in Parameter validation. Additionally, unlike the less secure versions of these functions, if format doesn't specify a valid format, an invalid parameter exception is generated. If execution is allowed to continue, these functions return an error code and set errno to that error code. The default error code is EINVAL if a more specific value doesn't apply.

Remarks

Each of these functions takes a pointer to an argument list, and then formats and writes the given data to the console. _vcwprintf_s is the wide-character version of _vcprintf_s. It takes a wide-character string as an argument.

The versions of these functions that have the _l suffix are identical except that they use the locale parameter that's passed in instead of the current locale.

Important

Ensure that format is not a user-defined string. For more information, see Avoiding buffer overruns.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_vtcprintf_s	_vcprintf_s	_vcprintf_s	_vcwprintf_s
_vtcprintf_s_l	_vcprintf_s_l	_vcprintf_s_l	_vcwprintf_s_l

Requirements

Routine	Required header	Optional headers
_vcprintf_s, _vcprintf_s_l	<conio.h> and <stdarg.h>	<varargs.h>*
_vcwprintf_s, _vcwprintf_s_l	<conio.h> or <wchar.h>, and <stdarg.h>	<varargs.h>*

* Required for UNIX V compatibility.

For more compatibility information, see Compatibility.

Important

Starting in Windows 10 version 2004 (build 19041), the printf family of functions prints exactly representable floating point numbers according to the IEEE 754 rules for rounding. In previous versions of Windows, exactly representable floating point numbers ending in '5' would always round up. IEEE 754 states that they must round to the closest even digit (also known as "Banker's Rounding"). For example, both printf("%1.0f", 1.5) and printf("%1.0f", 2.5) should round to 2. Previously, 1.5 would round to 2 and 2.5 would round to 3. This change only affects exactly representable numbers. For example, 2.35 (which, when represented in memory, is closer to 2.35000000000000008) continues to round up to 2.4. Rounding done by these functions now also respects the floating point rounding mode set by fesetround. Previously, rounding always chose FE_TONEAREST behavior. This change only affects programs built using Visual Studio 2019 version 16.2 and later. To use the legacy floating point rounding behavior, link with legacy_stdio_float_rounding.obj.

Example

// crt_vcprintf_s.cpp
#include <conio.h>
#include <stdarg.h>

// An error formatting function used to print to the console.
int eprintf_s(const char* format, ...)
{
    va_list args;
    va_start(args, format);
    int result = _vcprintf_s(format, args);
    va_end(args);
    return result;
}

int main()
{
    eprintf_s("(%d:%d): Error %s%d : %s\n", 10, 23, "C", 2111,
              "<some error text>");
    eprintf_s("    (Related to symbol '%s' defined on line %d).\n",
              "<symbol>", 5 );
}

(10,23): Error C2111 : <some error text>
    (Related to symbol '<symbol>' defined on line 5).

See also

Stream I/O
vprintf functions
_cprintf, _cprintf_l, _cwprintf, _cwprintf_l
fprintf, _fprintf_l, fwprintf, _fwprintf_l
printf, _printf_l, wprintf, _wprintf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
va_arg, va_copy, va_end, va_start