Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -7724,6 +7724,50 @@
 #define INIT_MODCTL
 #endif
 
+#if SANITIZER_INTERCEPT_STRTONUM
+INTERCEPTOR(long long, strtonum, const char *nptr, long long minval,
+            long long maxval, const char **errstr) {
+  void *ctx;
+  INTMAX_T res = 0;
+  COMMON_INTERCEPTOR_ENTER(ctx, strtonum, nptr, minval, maxval, errstr);
+  const char *rerrstr;
+  if (!errstr)
+    errstr = &rerrstr;
+
+  if (minval > maxval) {
+    *errstr = "invalid";
+  } else {
+    int saved_errno = errno;
+    errno = 0;
+
+    char *real_endptr;
+    res = REAL(strtoimax)(nptr, &real_endptr, 10);
+    StrtolFixAndCheck(ctx, nptr, nullptr, real_endptr, 10);
+    if (nptr == real_endptr || *real_endptr != '\0')
+      *errstr = "invalid";
+    else if ((res == INTMAX_MAX && errno == errno_ERANGE) || (maxval < res))
+       *errstr = "too large";
+    else if ((res == INTMAX_MIN && errno == errno_ERANGE) || (minval > res))
+      *errstr = "too small";
+    else
+      *errstr = nullptr;
+
+    errno = saved_errno;
+  }
+
+  COMMON_INTERCEPTOR_WRITE_RANGE(ctx, errstr, sizeof(*errstr));
+  if (*errstr) {
+    res = 0;
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, *errstr, REAL(strlen)(*errstr) + 1);
+  }
+
+  return res;
+}
+#define INIT_STRTONUM COMMON_INTERCEPT_FUNCTION(strtonum)
+#else
+#define INIT_STRTONUM
+#endif
+
 static void InitializeCommonInterceptors() {
   static u64 metadata_mem[sizeof(MetadataHashMap) / sizeof(u64) + 1];
   interceptor_metadata_map = new((void *)&metadata_mem) MetadataHashMap();
@@ -7988,6 +8032,7 @@
   INIT_SYSCTLGETMIBINFO;
   INIT_NL_LANGINFO;
   INIT_MODCTL;
+  INIT_STRTONUM;
 
   INIT___PRINTF_CHK;
 }
Index: lib/sanitizer_common/sanitizer_errno.cc
===================================================================
--- lib/sanitizer_common/sanitizer_errno.cc
+++ lib/sanitizer_common/sanitizer_errno.cc
@@ -24,6 +24,7 @@
 COMPILER_CHECK(errno_ENOMEM == ENOMEM);
 COMPILER_CHECK(errno_EBUSY == EBUSY);
 COMPILER_CHECK(errno_EINVAL == EINVAL);
+COMPILER_CHECK(errno_ERANGE == ERANGE);
 
 // EOWNERDEAD is not present in some older platforms.
 #if defined(EOWNERDEAD)
Index: lib/sanitizer_common/sanitizer_errno_codes.h
===================================================================
--- lib/sanitizer_common/sanitizer_errno_codes.h
+++ lib/sanitizer_common/sanitizer_errno_codes.h
@@ -25,6 +25,7 @@
 #define errno_ENOMEM 12
 #define errno_EBUSY 16
 #define errno_EINVAL 22
+#define errno_ERANGE 34
 
 // Those might not present or their value differ on different platforms.
 extern const int errno_EOWNERDEAD;
Index: lib/sanitizer_common/sanitizer_internal_defs.h
===================================================================
--- lib/sanitizer_common/sanitizer_internal_defs.h
+++ lib/sanitizer_common/sanitizer_internal_defs.h
@@ -363,6 +363,10 @@
 #define INT64_MAX              (__INT64_C(9223372036854775807))
 #undef UINT64_MAX
 #define UINT64_MAX             (__UINT64_C(18446744073709551615))
+#undef INTMAX_MIN
+#define INTMAX_MIN             INT64_MIN
+#undef INTMAX_MAX
+#define INTMAX_MAX             INT64_MAX
 #undef UINTPTR_MAX
 #if SANITIZER_WORDSIZE == 64
 # define UINTPTR_MAX           (18446744073709551615UL)
Index: lib/sanitizer_common/sanitizer_platform_interceptors.h
===================================================================
--- lib/sanitizer_common/sanitizer_platform_interceptors.h
+++ lib/sanitizer_common/sanitizer_platform_interceptors.h
@@ -528,5 +528,6 @@
 #define SANITIZER_INTERCEPT_SYSCTLGETMIBINFO SI_NETBSD
 #define SANITIZER_INTERCEPT_NL_LANGINFO (SI_NETBSD || SI_FREEBSD)
 #define SANITIZER_INTERCEPT_MODCTL SI_NETBSD
+#define SANITIZER_INTERCEPT_STRTONUM SI_NETBSD
 
 #endif  // #ifndef SANITIZER_PLATFORM_INTERCEPTORS_H
Index: test/sanitizer_common/TestCases/NetBSD/strtonum.cc
===================================================================
--- /dev/null
+++ test/sanitizer_common/TestCases/NetBSD/strtonum.cc
@@ -0,0 +1,58 @@
+// RUN: %clangxx -O0 -g %s -o %t && %run %t 2>&1 | FileCheck %s
+
+#define _OPENBSD_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+  const char *errstr;
+
+  printf("strtonum\n");
+
+  long long l = strtonum("100", 1, 100, &errstr);
+  if (errstr)
+    abort();
+  printf("%lld\n", l);
+
+  l = strtonum("200", 1, 100, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  l = strtonum("300", 1000, 1001, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  l = strtonum("abc", 1000, 1001, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  l = strtonum("1000", 1001, 1000, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  l = strtonum("1000abc", 1000, 1001, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  l = strtonum("1000.0", 1000, 1001, &errstr);
+  if (!errstr)
+    abort();
+  printf("%s\n", errstr);
+
+  // CHECK: strtonum
+  // CHECK: 100
+  // CHECK: too large
+  // CHECK: too small
+  // CHECK: invalid
+  // CHECK: invalid
+  // CHECK: invalid
+  // CHECK: invalid
+
+  return 0;
+}