[gn build] Allow option to build with asan/tsan/ubsan

[aeubanks]

format

[aeubanks]

I got asan to fire on some out of bounds stuff with this change, but couldn't get ubsan to trigger on integer overflow for some reason. -fsanitize=undefined is in the ninja files, so maybe I just didn't trip it in the right way.

[vitalybuka]

In D88056#2286450, @aeubanks wrote:

I got asan to fire on some out of bounds stuff with this change, but couldn't get ubsan to trigger on integer overflow for some reason. -fsanitize=undefined is in the ninja files, so maybe I just didn't trip it in the right way.

maybe because "-fsanitize=local-bounds is not included in -fsanitize=undefined" https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html

[vitalybuka]

In D88056#2286473, @vitalybuka wrote:

In D88056#2286450, @aeubanks wrote:

I got asan to fire on some out of bounds stuff with this change, but couldn't get ubsan to trigger on integer overflow for some reason. -fsanitize=undefined is in the ninja files, so maybe I just didn't trip it in the right way.

I assume you are asking about the same code which triggers asan and you expect some ubsan report there.
Never mind if the question was about -fsanitize=signed-integer-overflow

[aeubanks]

In D88056#2286494, @vitalybuka wrote:

In D88056#2286473, @vitalybuka wrote:

In D88056#2286450, @aeubanks wrote:

I got asan to fire on some out of bounds stuff with this change, but couldn't get ubsan to trigger on integer overflow for some reason. -fsanitize=undefined is in the ninja files, so maybe I just didn't trip it in the right way.

I assume you are asking about the same code which triggers asan and you expect some ubsan report there.
Never mind if the question was about -fsanitize=signed-integer-overflow

Poorly worded on my part, I meant -fsanitize=signed-integer-overflow on different code. (I was trying to repro a bot failure caught by ubsan but couldn't repro it with this, I was wondering if I got something wrong, but separately was able to get asan to trigger on some bad code, so at least I know that the flags are probably correct)

[rnk]

Looks good to me. My only question is whether to optimistically assume these work out of the box on Mac, and to relax the asserts. Let's wait for input from Nico, though.

[thakis]

I believe I used this (by hacking up the gn files) locally on mac a while ago, but I'm not sure. LG, I'll try asan on mac and relax the assert if it works.

Naming-wise, it's maybe unclear if use_?san turns on the sanitizer for building llvm itself or for the output of clang or what, but it's consistent with the existing is_clang so maybe let's not worry about this too much for now.

llvm/utils/gn/build/BUILD.gn

if (is_clang) {
     }
     if (use_relative_paths_in_debug_info) {
       cflags += [
         "-fdebug-compilation-dir",
         ".",
       ]
     }
   }
+
+  if (use_ubsan) {
+    assert(is_clang && current_os == "linux",
+           "ubsan only supported on Linux/Clang")
+    cflags += [ "-fsanitize=undefined" ]
+    ldflags += [ "-fsanitize=undefined" ]
+  }
+
+  if (use_asan) {
+    assert(is_clang && current_os == "linux",
+           "asan only supported on Linux/Clang")
+    cflags += [ "-fsanitize=address" ]
+    ldflags += [ "-fsanitize=address" ]
+  }
+
+  if (use_tsan) {
+    assert(is_clang && current_os == "linux",
+           "tsan only supported on Linux/Clang")
+    cflags += [ "-fsanitize=thread" ]
+    ldflags += [ "-fsanitize=thread" ]
+  }
 }
 
 config("no_exceptions") {
   if (host_os != "win") {
     cflags_cc = [ "-fno-exceptions" ]
   }
 }
 

llvm/utils/gn/build/buildflags.gni

 declare_args() {
   # Whether to build with debug information.
   is_debug = false
+
+  # Whether to build with tsan.
+  use_tsan = false
+
+  # Whether to build with ubsan.
+  use_ubsan = false
+
+  # Whether to build with asan.
+  use_asan = false
 }
 
 # args that depend on other args must live in a later declare_args() block.
 declare_args() {
   # Whether to build with optimizations.
   is_optimized = !is_debug
 
   # Whether to enable assertions.
   llvm_enable_assertions = true
 
   # Whether to enable expensive checks.
   llvm_enable_expensive_checks = false
 }