1.\" $OpenBSD: clang-local.1,v 1.24 2024/06/02 15:40:43 deraadt Exp $ 2.\" 3.\" Copyright (c) 2016 Pascal Stumpf <pascal@stumpf.co> 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.\" 18.Dd $Mdocdate: June 2 2024 $ 19.Dt CLANG-LOCAL 1 20.Os 21.Sh NAME 22.Nm clang-local 23.Nd OpenBSD-specific behavior of LLVM/clang 24.Sh DESCRIPTION 25On 26.Ox , 27the LLVM/clang compiler exhibits the following characteristics: 28.Bl -dash 29.It 30.Nm clang 31does not search under 32.Pa /usr/local 33for include files or libraries: 34as a system compiler, it only searches the system paths by default. 35.It 36.Nm clang 37comes with stack protection enabled by default, equivalent to the 38.Fl fstack-protector-strong 39option on other systems. 40The system will report any violation of the stack protector cookie along 41with the function name via 42.Xr syslog 3 43at 44.Dv LOG_CRIT 45priority. 46.It 47.Nm clang 48will generate PIE code by default, allowing the system to load the resulting 49binary at a random location. 50This behavior can be turned off by passing 51.Fl fno-pie 52to the compiler and 53.Fl nopie 54to the linker. 55It is also turned off when the 56.Fl pg 57flag is used. 58.It 59The 60.Fl fstrict-aliasing 61option is turned off by default unless 62.Fl Ofast 63has been selected. 64.It 65.Nm clang 66does not store its version string in objects. 67There is no option to control this. 68.It 69The 70.Fl p 71flag is an alias of 72.Fl pg . 73.It 74.Nm clang 75does not warn for passing pointer arguments or assignment with 76different signedness outside of 77.Fl pedantic . 78This can be 79re-enabled with the 80.Fl Wpointer-sign 81flag. 82.It 83The warning option 84.Fl Waddress-of-packed-member 85is disabled by default. 86.It 87Color diagnostic messages are disabled by default and can be re-enabled with 88.Fl fdiagnostics-color . 89.It 90The 91.Fl fwrapv 92option to treat signed integer overflows as defined is enabled by default to 93prevent dangerous optimizations which could remove security critical overflow 94checks. 95.It 96The base system includes the ubsan_minimal sanitizer runtime 97but not the fully-featured ubsan runtime. 98See the documentation for the 99.Fl fsanitize-minimal-runtime 100flag. 101.It 102The 103.Xr malloc 3 , 104.Xr calloc 3 , 105.Xr realloc 3 , 106.Xr strdup 3 , 107.Xr strndup 3 , 108.Xr valloc 3 109and 110.Xr free 3 111builtins are disabled to prevent undesirable optimizations of calls to 112these functions. 113.It 114.Nm clang 115includes a security pass that exchanges some ROP-friendly instructions 116with safer alternatives on i386 and amd64. 117This can be disabled with the 118.Fl fno-fixup-gadgets 119option. 120.It 121.Nm clang 122includes a security pass that can clear the return address on the 123stack upon return from calling a function, on i386 and amd64. 124This can be enabled with the 125.Fl fret-clean 126option. 127.It 128.Nm clang 129includes the retguard security feature on amd64, arm64, mips64, powerpc 130and powerpc64. 131This feature can be disabled with the 132.Fl fno-ret-protector 133or 134.Fl fno-stack-protector 135options. 136.It 137.Nm clang 138has 139.Fl mretpoline 140enabled by default on amd64 to protect against branch target injection attacks. 141It can be disabled with 142.Fl mno-retpoline . 143.It 144A new warning for 145.Cm %n 146format specifier usage in 147.Xr printf 3 148family functions has been added. 149.El 150.Sh SEE ALSO 151.Xr clang 1 152