Index: lib/libthr/Makefile
===================================================================
--- lib/libthr/Makefile
+++ lib/libthr/Makefile
@@ -68,6 +68,11 @@
 .endif
 .if !defined(NO_PIC)
 SYMLINKS+=lib${LIB}.so ${LIBDIR}/libpthread.so
+beforeinstall:
+	if ${NM} -u ${SHLIB_NAME_FULL} | grep ' mem'; then \
+	   echo "Found interposable call to memory function: "; \
+	   ${NM} -u ${SHLIB_NAME_FULL} | grep ' mem'; false; \
+	fi
 .endif
 .if ${MK_PROFILE} != "no"
 SYMLINKS+=lib${LIB}_p.a ${LIBDIR}/libpthread_p.a
Index: lib/libthr/thread/Makefile.inc
===================================================================
--- lib/libthr/thread/Makefile.inc
+++ lib/libthr/thread/Makefile.inc
@@ -30,6 +30,7 @@
 	thr_list.c \
 	thr_kern.c \
 	thr_kill.c \
+	thr_libcdeps.c \
 	thr_main_np.c \
 	thr_malloc.c \
 	thr_multi_np.c \
@@ -59,3 +60,7 @@
 	thr_symbols.c \
 	thr_umtx.c \
 	thr_yield.c
+
+# Avoid interposable function calls to memcpy(), etc. to avoid crashes when
+# running applications linked with sanitizers.
+SHARED_CFLAGS+=-DAVOID_INTERPOSABLE_LIBC_FUNCTIONS
Index: lib/libthr/thread/thr_libcdeps.c
===================================================================
--- /dev/null
+++ lib/libthr/thread/thr_libcdeps.c
@@ -0,0 +1,59 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2020 Alex Richardson <arichardson@FreeBSD.org>
+ *
+ * This software was developed by SRI International and the University of
+ * Cambridge Computer Laboratory (Department of Computer Science and
+ * Technology) under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the
+ * DARPA SSITH research programme.
+ *
+ * This work was supported by Innovate UK project 105694, "Digital Security by
+ * Design (DSbD) Technology Platform Prototype".
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef AVOID_INTERPOSABLE_LIBC_FUNCTIONS
+#include <sys/cdefs.h>
+#include <stddef.h>
+
+void *memcpy(void *, const void *, size_t) __hidden;
+void *memmove(void *, const void *, size_t) __hidden;
+void *memset(void *, int, size_t) __hidden;
+
+/*
+ * This file exists to avoid interposable calls to libc functions inside
+ * functions that are intercepted by sanitizer runtimes. One example where we
+ * need to avoid interposable function calls is the copy of the ucontext_t
+ * argument in handle_signal() as this results in crashes when linking
+ * applications with ThreadSanitizer. Another example is the libthr-internal
+ * allocator that calls memset and memcpy. With interposable function calls
+ * ThreadSanitizer reports false-positive race conditions since the locks
+ * guarding the allocation functions cannot be seen by the TSan runtime.
+ *
+ * Note: This file is only needed for the shared library build.
+ */
+#include "../../libc/string/memmove.c"
+__strong_reference(memmove, memcpy);
+#undef wsize
+#include "../../libc/string/memset.c"
+
+#endif