[Sanitizer] Undefined Behavior Sanitizer support proposal for DragonFlyBSD

[krytarowski]

This contains unrelated code to ubsan/dragonflybsd. While there can you remove unsupported code for other OSs you introduced? That was never operational?

[devnexen]

In D89631#2337028, @krytarowski wrote:

This contains unrelated code to ubsan/dragonflybsd. While there can you remove unsupported code for other OSs you introduced? That was never operational?

Well DragonFly does not support sanitizers that s kind of mandatory or should I cut into different differential ?

[krytarowski]

Please, First remove unused + unusable code for already introduced OS. At most cutting it to ubsan.

[devnexen]

Focusing on ubsan change only

[vitalybuka]

I have nothing against the patch in general but I am uncomfortable with the fact that I can accidentally undo this change and very likely I will know nothing about breakages for weeks.
Build bot which run just few times a week could be super helpful.

Also I am personally not sure if such unpopular distribution is worth of supporting, But some patches are already accepted by llvm, so this one is LGTM.
I hope we will not need to add a lot of special cases in other sanitizers and just keep them as unsupported.

compiler-rt/lib/ubsan/ubsan_platform.h

 //===-- ubsan_platform.h ----------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Defines the platforms which UBSan is supported at.
 //
 //===----------------------------------------------------------------------===//
 #ifndef UBSAN_PLATFORM_H
 #define UBSAN_PLATFORM_H
 
 // Other platforms should be easy to add, and probably work as-is.
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__) ||        \
-    defined(__NetBSD__) || \
+    defined(__NetBSD__) || defined(__DragonFly__) \
     (defined(__sun__) && defined(__svr4__)) || \
     defined(_WIN32) || defined(__Fuchsia__) || defined(__rtems__)
 # define CAN_SANITIZE_UB 1
 #else
 # define CAN_SANITIZE_UB 0
 #endif
 
 #endif