1.\" 2.\" This file and its contents are supplied under the terms of the 3.\" Common Development and Distribution License ("CDDL"), version 1.0. 4.\" You may only use this file in accordance with the terms of version 5.\" 1.0 of the CDDL. 6.\" 7.\" A full copy of the text of the CDDL should have accompanied this 8.\" source. A copy of the CDDL is also available via the Internet at 9.\" http://www.illumos.org/license/CDDL. 10.\" 11.\" 12.\" Copyright 2024 Oxide Computer Company 13.\" 14.Dd October 27, 2024 15.Dt STDC_FIRST_TRAILING_ZERO 9F 16.Os 17.Sh NAME 18.Nm stdc_first_trailing_zero , 19.Nm stdc_first_trailing_zero_uc , 20.Nm stdc_first_trailing_zero_us , 21.Nm stdc_first_trailing_zero_ui , 22.Nm stdc_first_trailing_zero_ul , 23.Nm stdc_first_trailing_zero_ull 24.Nd find index of least significant zero bit 25.Sh SYNOPSIS 26.In sys/stdbit.h 27.Ft "unsigned int" 28.Fo stdc_first_trailing_zero 29.Fa "generic_value_type value" 30.Fc 31.Ft "unsigned int" 32.Fo stdc_first_trailing_zero_uc 33.Fa "unsigned char value" 34.Fc 35.Ft "unsigned int" 36.Fo stdc_first_trailing_zero_us 37.Fa "unsigned short value" 38.Fc 39.Ft "unsigned int" 40.Fo stdc_first_trailing_zero_ui 41.Fa "unsigned int value" 42.Fc 43.Ft "unsigned int" 44.Fo stdc_first_trailing_zero_ul 45.Fa "unsigned long value" 46.Fc 47.Ft "unsigned int" 48.Fo stdc_first_trailing_zero_ull 49.Fa "unsigned long long value" 50.Fc 51.Sh DESCRIPTION 52The 53.Fn stdc_first_trailing_zero 54family of functions returns the 1s-based index of the first zero bit in 55.Fa value 56starting at the least significant bit. 57If there is no zero bit in 58.Fa value 59then zero is returned. 60.Pp 61The 62.Fn stdc_first_trailing_zero 63function is generic and will operate on all 8, 16, 32, and 64-bit 64unsigned integers; however, it is only available in C23. 65The other functions all operate on a specific integer type, but 66otherwise behave the same and are available regardless of the C language 67version. 68.Sh CONTEXT 69These functions may be called from 70.Sy user , 71.Sy kernel , 72or 73.Sy interrupt 74context. 75.Sh RETURN VALUES 76The functions in the 77.Fn stdc_first_trailing_zero 78family always return the index of the first trailing 79zero bit in 80.Fa value 81plus one. 82Otherwise, if there are no zero bits in 83.Fa value , 840 will be returned. 85These functions cannot fail. 86.Sh INTERFACE STABILITY 87.Sy Committed 88.Sh SEE ALSO 89.Xr stdc_first_trailing_zero 3C , 90.Xr stdc_bit_ceil 9F , 91.Xr stdc_bit_floor 9F , 92.Xr stdc_bit_width 9F , 93.Xr stdc_count_ones 9F , 94.Xr stdc_count_zeros 9F , 95.Xr stdc_first_leading_one 9F , 96.Xr stdc_first_leading_zero 9F , 97.Xr stdc_first_trailing_one 9F , 98.Xr stdc_has_single_bit 9F , 99.Xr stdc_leading_ones 9F , 100.Xr stdc_leading_zeros 9F , 101.Xr stdc_trailing_ones 9F , 102.Xr stdc_trailing_zeros 9F 103