`_get_printf_count_output`

Article
10/26/2022

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.