diff --git a/CMakeLists.txt b/CMakeLists.txt
index 18407e864523..cb013d6cd588 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -211,8 +211,8 @@ if(NOT PYTHON_ONLY)
 
 endif(NOT PYTHON_ONLY)
 
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall ${CXX_ISYSTEM_DIRS}")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Werror=undef")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror=undef ${CXX_ISYSTEM_DIRS}")
 
 add_subdirectory(src)
 add_subdirectory(introspection)
diff --git a/src/cc/frontends/clang/CMakeLists.txt b/src/cc/frontends/clang/CMakeLists.txt
index f45365fc02c6..1469c5cd9ae4 100644
--- a/src/cc/frontends/clang/CMakeLists.txt
+++ b/src/cc/frontends/clang/CMakeLists.txt
@@ -7,6 +7,8 @@ if(DEFINED BCC_CUR_CPU_IDENTIFIER)
 endif()
 if(DEFINED BCC_BACKUP_COMPILE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DBCC_BACKUP_COMPILE='${BCC_BACKUP_COMPILE}'")
+else()
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DBCC_BACKUP_COMPILE=0")
 endif()
 
 add_library(clang_frontend-objects OBJECT loader.cc b_frontend_action.cc tp_frontend_action.cc kbuild_helper.cc)
diff --git a/src/cc/usdt/usdt.cc b/src/cc/usdt/usdt.cc
index a6213653ec6e..24960e52a88b 100644
--- a/src/cc/usdt/usdt.cc
+++ b/src/cc/usdt/usdt.cc
@@ -36,15 +36,15 @@ Location::Location(uint64_t addr, const std::string &bin_path, const char *arg_f
     : address_(addr),
       bin_path_(bin_path) {
 
-#ifdef __aarch64__
+#if defined(__aarch64__)
   ArgumentParser_aarch64 parser(arg_fmt);
-#elif __loongarch64
+#elif defined(__loongarch64)
   ArgumentParser_loongarch64 parser(arg_fmt);
-#elif __powerpc64__
+#elif defined(__powerpc64__)
   ArgumentParser_powerpc64 parser(arg_fmt);
-#elif __s390x__
+#elif defined(__s390x__)
   ArgumentParser_s390x parser(arg_fmt);
-#elif __riscv
+#elif defined(__riscv)
   ArgumentParser_riscv64 parser(arg_fmt);
 #else
   ArgumentParser_x64 parser(arg_fmt);
diff --git a/tests/cc/test_usdt_args.cc b/tests/cc/test_usdt_args.cc
index d9c4d46a394d..db77fb426fa5 100644
--- a/tests/cc/test_usdt_args.cc
+++ b/tests/cc/test_usdt_args.cc
@@ -59,15 +59,15 @@ static void verify_register(USDT::ArgumentParser &parser, int arg_size,
 
 TEST_CASE("test usdt argument parsing", "[usdt]") {
   SECTION("parse failure") {
-#ifdef __aarch64__
+#if defined(__aarch64__)
     USDT::ArgumentParser_aarch64 parser("4@[x32,200]");
-#elif __loongarch64
+#elif defined(__loongarch64)
     USDT::ArgumentParser_loongarch64 parser("4@[$r32,200]");
-#elif __powerpc64__
+#elif defined(__powerpc64__)
     USDT::ArgumentParser_powerpc64 parser("4@-12(42)");
-#elif __s390x__
+#elif defined(__s390x__)
     USDT::ArgumentParser_s390x parser("4@-12(%r42)");
-#elif __riscv
+#elif defined(__riscv)
     USDT::ArgumentParser_riscv64 parser("4@20(s35)");
 #elif defined(__x86_64__)
     USDT::ArgumentParser_x64 parser("4@i%ra+1r");
@@ -82,7 +82,7 @@ TEST_CASE("test usdt argument parsing", "[usdt]") {
     REQUIRE(i < 10);
   }
   SECTION("argument examples from the Python implementation") {
-#ifdef __aarch64__
+#if defined(__aarch64__)
     USDT::ArgumentParser_aarch64 parser(
         "-1@x0 4@5 8@[x12] -4@[x30,-40] -4@[x31,-40] 8@[sp, 120]");
     verify_register(parser, -1, "regs[0]");
@@ -91,7 +91,7 @@ TEST_CASE("test usdt argument parsing", "[usdt]") {
     verify_register(parser, -4, "regs[30]", -40);
     verify_register(parser, -4, "sp", -40);
     verify_register(parser, 8, "sp", 120);
-#elif __loongarch64
+#elif defined(__loongarch64)
     USDT::ArgumentParser_loongarch64 parser(
 	"-1@$r0 4@5 8@[$r12] -4@[$r30,-40] -4@[$r3,-40] 8@[sp, 120]");
     verify_register(parser, -1, "regs[0]");
@@ -100,7 +100,7 @@ TEST_CASE("test usdt argument parsing", "[usdt]") {
     verify_register(parser, -4, "regs[30]", -40);
     verify_register(parser, -4, "sp", -40);
     verify_register(parser, 8, "sp", 120);
-#elif __powerpc64__
+#elif defined(__powerpc64__)
     USDT::ArgumentParser_powerpc64 parser(
         "-4@0 8@%r0 8@i0 4@0(%r0) -2@0(0) "
         "1@0 -2@%r3 -8@i9 -1@0(%r4) -4@16(6) "
@@ -144,7 +144,7 @@ TEST_CASE("test usdt argument parsing", "[usdt]") {
     verify_register(parser, 2, 1097);
     verify_register(parser, 4, "gpr[30]", 108);
     verify_register(parser, -2, "gpr[31]", -4);
-#elif __s390x__
+#elif defined(__s390x__)
     USDT::ArgumentParser_s390x parser(
         "-4@%r0 8@%r0 8@0 4@0(%r0) -2@0(%r0) "
         "1@%r0 -2@%r3 -8@9 -1@0(%r4) -4@16(%r6) "
@@ -188,7 +188,7 @@ TEST_CASE("test usdt argument parsing", "[usdt]") {
     verify_register(parser, 2, 1097);
     verify_register(parser, 4, "gprs[7]", 108);
     verify_register(parser, -2, "gprs[6]", -4);
-#elif __riscv
+#elif defined(__riscv)
     USDT::ArgumentParser_riscv64 parser(
 	"-4@s5 -4@a0 4@20(s1) -4@-1 8@-72(s0) 8@0");
     verify_register(parser, -4, "s5");
diff --git a/tests/python/include/folly/tracing/StaticTracepoint.h b/tests/python/include/folly/tracing/StaticTracepoint.h
index 858b7dbc0cee..8e580309fd9f 100644
--- a/tests/python/include/folly/tracing/StaticTracepoint.h
+++ b/tests/python/include/folly/tracing/StaticTracepoint.h
@@ -17,7 +17,7 @@
 #pragma once
 
 #if defined(__ELF__) && (defined(__x86_64__) || defined(__i386__)) && \
-    !FOLLY_DISABLE_SDT
+    !(defined(FOLLY_DISABLE_SDT) && FOLLY_DISABLE_SDT)
 
 #include <folly/tracing/StaticTracepoint-ELFx86.h>