get-printf-count-output.md

description	title	ms.date	api_name	api_location	api_type	topic_type	f1_keywords	helpviewer_keywords
Learn more about: _get_printf_count_output	_get_printf_count_output	3/9/2021	_get_printf_count_output	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-stdio-l1-1-0.dll	DLLExport	apiref	get_printf_count_output _get_printf_count_output	%n format get_printf_count_output function _get_printf_count_output function

_get_printf_count_output

Indicates whether printf, _printf_l, wprintf, _wprintf_l-family functions support the %n format.

Syntax

int _get_printf_count_output();

Return value

Non-zero if %n is supported; 0 if %n isn't supported.

Remarks

If %n isn't supported (the default), any %n found in the format string of one of the printf functions invokes the invalid parameter handler, as described in Parameter validation. If %n support is enabled (see _set_printf_count_output), then %n behaves as described in Format specification syntax: printf and wprintf functions.

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`.

Requirements

Routine	Required header
_get_printf_count_output	<stdio.h>

For more compatibility information, see Compatibility.

Example

See the example for _set_printf_count_output.

See also

_set_printf_count_output