_vcprintf, _vcprintf_l, _vcwprintf, _vcwprintf_l

Writes formatted output to the console by using a pointer to a list of arguments. More secure versions of these functions are available, see _vcprintf_s, _vcprintf_s_l, _vcwprintf_s, _vcwprintf_s_l.

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(
   const char* format,
   va_list argptr
);
int _vcprintf_l(
   const char* format,
   _locale_t locale,
   va_list argptr
);
int _vcwprintf(
   const wchar_t* format,
   va_list argptr
);
int _vcwprintf_l(
   const wchar_t* format,
   _locale_t locale,
   va_list argptr
);

Parameters

format
Format specification.

argptr
Pointer to list of arguments.

locale
The locale to use.

For more information, see Format specification syntax.

Return value

The number of characters written, or a negative value if an output error occurs. If format is a null pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, errno is set to EINVAL, and -1 is returned.

Remarks

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

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

Important

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

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`.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_vtcprintf	_vcprintf	_vcprintf	_vcwprintf
_vtcprintf_l	_vcprintf_l	_vcprintf_l	_vcwprintf_l

Requirements

Routine	Required header	Optional headers
_vcprintf, _vcprintf_l	<conio.h> and <stdarg.h>	<varargs.h>*
_vcwprintf, _vcwprintf_l	<conio.h> or <wchar.h>, and <stdarg.h>	<varargs.h>*

* Required for UNIX V compatibility.

For more compatibility information, see Compatibility.

Example

// crt_vcprintf.cpp
// compile with: /c
#include <conio.h>
#include <stdarg.h>

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

int main()
{
    eprintf("(%d:%d): Error %s%d : %s\n", 10, 23, "C", 2111,
           "<some error text>");
    eprintf("    (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