From: https://github.com/bpftrace/bpftrace/pull/4655

From: =?UTF-8?q?Viktor=20Mal=C3=ADk?= <viktor.malik@gmail.com>
Date: Thu, 25 Sep 2025 13:34:17 +0200
Subject: [PATCH] CMake: Enable UBSan builds (#4655)

Add new CMake option `BUILD_UBSAN` which will add `-fsanitize=undefined`
to the build. This helps to identify undefined behavior.

Signed-off-by: Viktor Malik <viktor.malik@gmail.com>
---
 CMakeLists.txt         |  1 +
 src/CMakeLists.txt     | 13 +++++++++++++
 src/aot/CMakeLists.txt |  4 ++++
 tests/CMakeLists.txt   |  5 +++++
 4 files changed, 23 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 898ec2f85560..5bb09a2e56be 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,7 @@ set(HARDENED_STDLIB OFF CACHE BOOL "Enable hardened definitions for standard lib
 set(STATIC_LINKING OFF CACHE BOOL "Build bpftrace as a statically linked executable")
 
 set(BUILD_ASAN OFF CACHE BOOL "Build bpftrace with -fsanitize=address")
+set(BUILD_UBSAN OFF CACHE BOOL "Build bpftrace with -fsanitize=undefined")
 set(ENABLE_MAN ON CACHE BOOL "Build man pages")
 set(BUILD_TESTING ON CACHE BOOL "Build test suite")
 set(ENABLE_TEST_VALIDATE_CODEGEN ON CACHE BOOL "Run LLVM IR validation tests")
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0432e6106e6d..d5432c0995d3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -2,6 +2,12 @@ if(HAVE_BFD_DISASM)
   set(BFD_DISASM_SRC bfd-disasm.cpp)
 endif()
 
+if (BUILD_UBSAN)
+  # This adds -fsanitize=undefined to all below compiler invocations, including
+  # subdirectories.
+  add_compile_options("-fsanitize=undefined")
+endif()
+
 add_library(required_resources required_resources.cpp)
 add_dependencies(required_resources parser)
 
@@ -201,6 +207,13 @@ if (BUILD_ASAN)
   target_link_options(bpftrace PUBLIC "-fsanitize=address")
 endif()
 
+if (BUILD_UBSAN)
+  # We do not use add_link_options here since it doesn't work for some reason.
+  # Instead, just pass -fsanitize=undefined to the linker when linking the
+  # bpftrace target.
+  target_link_options(bpftrace PUBLIC "-fsanitize=undefined")
+endif()
+
 if (STATIC_LINKING)
   if(ANDROID)
     target_link_libraries(libbpftrace "-Wl,-Bdynamic" "-ldl" "-lm" "-lz")
diff --git a/src/aot/CMakeLists.txt b/src/aot/CMakeLists.txt
index 1323bdacb6df..5267e4a1c19e 100644
--- a/src/aot/CMakeLists.txt
+++ b/src/aot/CMakeLists.txt
@@ -34,3 +34,7 @@ if(BUILD_ASAN)
   target_compile_options(bpftrace-aotrt PUBLIC "-fsanitize=address")
   target_link_options(bpftrace-aotrt PUBLIC "-fsanitize=address")
 endif()
+
+if(BUILD_UBSAN)
+  target_link_options(bpftrace-aotrt PUBLIC "-fsanitize=undefined")
+endif()
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b6002e8075ff..141b44d5a30e 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -94,6 +94,11 @@ if(BUILD_ASAN)
   target_link_options(bpftrace_test PUBLIC "-fsanitize=address")
 endif()
 
+if(BUILD_UBSAN)
+  target_compile_options(bpftrace_test PUBLIC "-fsanitize=undefined")
+  target_link_options(bpftrace_test PUBLIC "-fsanitize=undefined")
+endif()
+
 # bpftrace tests require (at minimum) version 1.11.
 # There's no great way to enforce a minimum version from cmake -- the cmake
 # modules don't respect minimum requested version.