diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -498,6 +498,21 @@
 
 append_list_if(MINGW -fms-extensions SANITIZER_COMMON_CFLAGS)
 
+# When lsan scans the stack for detecting reachable pointers, it's possible for
+# a leaked pointer, which was pushed to the stack on an earlier function call,
+# to still exist on the stack when doing a leak check if that part of the stack
+# was not overwritten. In particular, if there's any uninitialized data in the
+# lsan runtime, and the SP we start from is sufficiently deep into the runtime,
+# then a leaked pointer could be marked as reachable. Such instances could be
+# mitigated by clobbering any uninitialized data. Note that this won't cover
+# all possible uninitialized stack contents, such as those used for register
+# spill slots, unused portions for alignment, or even local variables not
+# yet in scope at a certain point in the function.
+#
+# Note that this type of issue was discovered with lsan, but can apply to other
+# sanitizers.
+append_list_if(COMPILER_RT_HAS_TRIVIAL_AUTO_INIT -ftrivial-auto-var-init=pattern SANITIZER_COMMON_CFLAGS)
+
 # Set common link flags.
 # TODO: We should consider using the same model as libc++, that is use either
 # -nostdlib++ and --unwindlib=none if supported, or -nodefaultlibs otherwise.
diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
--- a/compiler-rt/cmake/config-ix.cmake
+++ b/compiler-rt/cmake/config-ix.cmake
@@ -93,6 +93,7 @@
 check_cxx_compiler_flag(--sysroot=.          COMPILER_RT_HAS_SYSROOT_FLAG)
 check_cxx_compiler_flag("-Werror -mcrc"      COMPILER_RT_HAS_MCRC_FLAG)
 check_cxx_compiler_flag(-fno-partial-inlining COMPILER_RT_HAS_FNO_PARTIAL_INLINING_FLAG)
+check_cxx_compiler_flag(-Werror -ftrivial-auto-var-init=pattern COMPILER_RT_HAS_TRIVIAL_AUTO_INIT)
 
 if(NOT WIN32 AND NOT CYGWIN)
   # MinGW warns if -fvisibility-inlines-hidden is used.