build: add build opts for enabling sanitizers

INSTALL.md

@@ -28,6 +28,20 @@ pro hand -p true -s false -n false SIGBUS
 pro hand -p true -s false -n false SIGSEGV
 ```
 
+### Sanitizers
+
+In order to use address sanitizer (`-Dasan`) and undefined behavior sanitizer (`-Dubsan`), you need to have version 18 of llvm and clang installed on your machine. You also have to build natively, since cross-compilation is not supported.
+
+macOS:
+```terminal
+brew install llvm@18
+```
+
+linux:
+```terminal
+apt-get install llvm-18 clang-18
+```
+
 ## Build
 
 Once you install `zig`, you're ready to build:
@@ -73,6 +87,12 @@ Supported values:
 Provide additional compiler flags. These propagate to all build artifacts and
 dependencies.
 
+#### `-Dasan`
+Enable address sanitizer. Supported in native builds only. Requires llvm and clang 18, see [prerequisites](#sanitizers).
+
+#### `-Dubsan`
+Enable undefined behavior sanitizer. Supported in native builds only. Requires llvm and clang 18, see [prerequisites](#sanitizers).
+
 <!-- ## LSP Integration -->
 
 <!-- ```console -->

build.zig

@@ -19,6 +19,8 @@ const BuildCfg = struct {
     mem_dbg: bool = false,
     c3dbg: bool = false,
     snapshot_validation: bool = false,
+    ubsan: bool = false,
+    asan: bool = false,
 };
 
 pub fn build(b: *std.Build) !void {
@@ -85,6 +87,18 @@ pub fn build(b: *std.Build) !void {
         "Binary name (Default: urbit)",
     ) orelse "urbit";
 
+    const asan = b.option(
+        bool,
+        "asan",
+        "Enable address sanitizer (native only, requires llvm & clang 18)",
+    ) orelse false;
+
+    const ubsan = b.option(
+        bool,
+        "ubsan",
+        "Enable undefined behavior sanitizer (native only, requires llvm & clang 18)",
+    ) orelse false;
+
     // Parse short git rev
     //
     var file = try std.fs.cwd().openFile(".git/logs/HEAD", .{});
@@ -118,6 +132,8 @@ pub fn build(b: *std.Build) !void {
         .mem_dbg = mem_dbg,
         .c3dbg = c3dbg,
         .snapshot_validation = snapshot_validation,
+        .asan = asan,
+        .ubsan = ubsan,
         .include_test_steps = !all,
     };
 
@@ -156,12 +172,38 @@ fn build_single(
 
     try global_flags.appendSlice(cfg.flags);
     try global_flags.appendSlice(&.{
-        "-fno-sanitize=all",
         "-g",
         "-Wall",
         "-Werror",
     });
 
+    if (!cfg.asan and !cfg.ubsan)
+        try global_flags.appendSlice(&.{
+            "-fno-sanitize=all",
+        });
+
+    if (cfg.asan and !cfg.ubsan)
+        try global_flags.appendSlice(&.{
+            "-Wno-deprecated",
+            "-fsanitize=address",
+            "-fno-sanitize=undefined",
+            "-fno-sanitize-trap=undefined",
+        });
+
+    if (!cfg.asan and cfg.ubsan)
+        try global_flags.appendSlice(&.{
+            "-fsanitize=undefined",
+            "-fno-sanitize-trap=undefined",
+        });
+
+    if (cfg.asan and cfg.ubsan)
+        try global_flags.appendSlice(&.{
+            "-Wno-deprecated",
+            "-fsanitize=address",
+            "-fsanitize=undefined",
+            "-fno-sanitize-trap=undefined",
+        });
+
     //
     // CFLAGS for Urbit Libs and Binaries
     //
@@ -861,6 +903,31 @@ fn build_single(
 
     urbit.linkLibC();
 
+    if (t.isDarwin()) {
+        // Requires llvm@18 homebrew installation
+        if (cfg.asan or cfg.ubsan)
+            urbit.addLibraryPath(.{
+                .cwd_relative = "/opt/homebrew/opt/llvm/lib/clang/18/lib/darwin",
+            });
+        if (cfg.asan) urbit.linkSystemLibrary("clang_rt.asan_osx_dynamic");
+        if (cfg.ubsan) urbit.linkSystemLibrary("clang_rt.ubsan_osx_dynamic");
+    }
+
+    if (t.os.tag == .linux) {
+        urbit.addLibraryPath(.{ .cwd_relative = "/usr/lib/clang/18/lib/linux" });
+        // Requires llvm-18 and clang-18 installation
+        if (t.cpu.arch == .x86_64) {
+            if (cfg.asan) urbit.linkSystemLibrary("clang_rt.asan-x86_64");
+            if (cfg.ubsan)
+                urbit.linkSystemLibrary("clang_rt.ubsan_standalone-x86_64");
+        }
+        if (t.cpu.arch == .aarch64) {
+            if (cfg.asan) urbit.linkSystemLibrary("clang_rt.asan-aarch64");
+            if (cfg.ubsan)
+                urbit.linkSystemLibrary("clang_rt.ubsan_standalone-aarch64");
+        }
+    }
+
     urbit.linkLibrary(vere);
     urbit.linkLibrary(pkg_noun);
     urbit.linkLibrary(pkg_c3);

pkg/c3/portable.h

@@ -129,7 +129,11 @@
 #       define U3_OS_LoomBits 30
 #   elif defined(U3_OS_osx)
 #     ifdef __LP64__
-#       define U3_OS_LoomBase 0x28000000000
+#       ifdef ASAN_ENABLED
+#         define U3_OS_LoomBase 0x728000000000
+#       else
+#         define U3_OS_LoomBase 0x28000000000
+#       endif
 #     else
 #       define U3_OS_LoomBase 0x4000000
 #     endif