Index: lib/asan/asan_shadow_setup.cc
===================================================================
--- lib/asan/asan_shadow_setup.cc
+++ lib/asan/asan_shadow_setup.cc
@@ -31,8 +31,7 @@
   CHECK_EQ(((end + 1) % GetMmapGranularity()), 0);
   uptr size = end - beg + 1;
   DecreaseTotalMmap(size);  // Don't count the shadow against mmap_limit_mb.
-  void *res = MmapFixedNoReserve(beg, size, name);
-  if (res != (void *)beg) {
+  if (!MmapFixedNoReserve(beg, size, name)) {
     Report(
         "ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
         "Perhaps you're using ulimit -v\n",
Index: lib/dfsan/dfsan.cc
===================================================================
--- lib/dfsan/dfsan.cc
+++ lib/dfsan/dfsan.cc
@@ -425,7 +425,8 @@
 
   InitializePlatformEarly();
 
-  MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr());
+  if (!MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr()))
+    Die();
 
   // Protect the region of memory we don't use, to preserve the one-to-one
   // mapping from application to shadow memory. But if ASLR is disabled, Linux
Index: lib/hwasan/hwasan_linux.cc
===================================================================
--- lib/hwasan/hwasan_linux.cc
+++ lib/hwasan/hwasan_linux.cc
@@ -44,8 +44,7 @@
   CHECK_EQ(((end + 1) % GetMmapGranularity()), 0);
   uptr size = end - beg + 1;
   DecreaseTotalMmap(size);  // Don't count the shadow against mmap_limit_mb.
-  void *res = MmapFixedNoReserve(beg, size, name);
-  if (res != (void *)beg) {
+  if (!MmapFixedNoReserve(beg, size, name)) {
     Report(
         "ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
         "Perhaps you're using ulimit -v\n",
Index: lib/msan/msan_linux.cc
===================================================================
--- lib/msan/msan_linux.cc
+++ lib/msan/msan_linux.cc
@@ -143,7 +143,7 @@
     if (map) {
       if (!CheckMemoryRangeAvailability(start, size))
         return false;
-      if ((uptr)MmapFixedNoReserve(start, size, kMemoryLayout[i].name) != start)
+      if (!MmapFixedNoReserve(start, size, kMemoryLayout[i].name))
         return false;
       if (common_flags()->use_madv_dontdump)
         DontDumpShadowMemory(start, size);
Index: lib/msan/msan_poisoning.cc
===================================================================
--- lib/msan/msan_poisoning.cc
+++ lib/msan/msan_poisoning.cc
@@ -139,7 +139,8 @@
       if (page_end != shadow_end) {
         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
       }
-      MmapFixedNoReserve(page_beg, page_end - page_beg);
+      if (!MmapFixedNoReserve(page_beg, page_end - page_beg))
+        Die();
     }
   }
 }
Index: lib/sanitizer_common/sanitizer_common.h
===================================================================
--- lib/sanitizer_common/sanitizer_common.h
+++ lib/sanitizer_common/sanitizer_common.h
@@ -88,8 +88,8 @@
 // Behaves just like MmapOrDie, but tolerates out of memory condition, in that
 // case returns nullptr.
 void *MmapOrDieOnFatalError(uptr size, const char *mem_type);
-void *MmapFixedNoReserve(uptr fixed_addr, uptr size,
-                         const char *name = nullptr);
+bool MmapFixedNoReserve(uptr fixed_addr, uptr size, const char *name = nullptr)
+     WARN_UNUSED_RESULT;
 void *MmapNoReserveOrDie(uptr size, const char *mem_type);
 void *MmapFixedOrDie(uptr fixed_addr, uptr size);
 // Behaves just like MmapFixedOrDie, but tolerates out of memory condition, in
Index: lib/sanitizer_common/sanitizer_internal_defs.h
===================================================================
--- lib/sanitizer_common/sanitizer_internal_defs.h
+++ lib/sanitizer_common/sanitizer_internal_defs.h
@@ -211,6 +211,7 @@
 # define LIKELY(x) (x)
 # define UNLIKELY(x) (x)
 # define PREFETCH(x) /* _mm_prefetch(x, _MM_HINT_NTA) */ (void)0
+# define WARN_UNUSED_RESULT
 #else  // _MSC_VER
 # define ALWAYS_INLINE inline __attribute__((always_inline))
 # define ALIAS(x) __attribute__((alias(x)))
@@ -229,6 +230,7 @@
 # else
 #  define PREFETCH(x) __builtin_prefetch(x)
 # endif
+# define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 #endif  // _MSC_VER
 
 #if !defined(_MSC_VER) || defined(__clang__)
Index: lib/sanitizer_common/sanitizer_posix_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix_libcdep.cc
+++ lib/sanitizer_common/sanitizer_posix_libcdep.cc
@@ -328,7 +328,7 @@
 }
 #endif
 
-void *MmapFixedNoReserve(uptr fixed_addr, uptr size, const char *name) {
+bool MmapFixedNoReserve(uptr fixed_addr, uptr size, const char *name) {
   int fd = name ? GetNamedMappingFd(name, size) : -1;
   unsigned flags = MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE;
   if (fd == -1) flags |= MAP_ANON;
@@ -338,12 +338,14 @@
                          RoundUpTo(size, PageSize), PROT_READ | PROT_WRITE,
                          flags, fd, 0);
   int reserrno;
-  if (internal_iserror(p, &reserrno))
+  if (internal_iserror(p, &reserrno)) {
     Report("ERROR: %s failed to "
            "allocate 0x%zx (%zd) bytes at address %zx (errno: %d)\n",
            SanitizerToolName, size, size, fixed_addr, reserrno);
+    return false;
+  }
   IncreaseTotalMmap(size);
-  return (void *)p;
+  return true;
 }
 
 uptr ReservedAddressRange::Init(uptr size, const char *name, uptr fixed_addr) {
Index: lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- lib/sanitizer_common/sanitizer_win.cc
+++ lib/sanitizer_common/sanitizer_win.cc
@@ -202,7 +202,7 @@
   return (void *)mapped_addr;
 }
 
-void *MmapFixedNoReserve(uptr fixed_addr, uptr size, const char *name) {
+bool MmapFixedNoReserve(uptr fixed_addr, uptr size, const char *name) {
   // FIXME: is this really "NoReserve"? On Win32 this does not matter much,
   // but on Win64 it does.
   (void)name;  // unsupported
@@ -215,11 +215,13 @@
   void *p = VirtualAlloc((LPVOID)fixed_addr, size, MEM_RESERVE | MEM_COMMIT,
                          PAGE_READWRITE);
 #endif
-  if (p == 0)
+  if (p == 0) {
     Report("ERROR: %s failed to "
            "allocate %p (%zd) bytes at %p (error code: %d)\n",
            SanitizerToolName, size, size, fixed_addr, GetLastError());
-  return p;
+    return false;
+  }
+  return true;
 }
 
 // Memory space mapped by 'MmapFixedOrDie' must have been reserved by
Index: lib/tsan/rtl/tsan_platform_posix.cc
===================================================================
--- lib/tsan/rtl/tsan_platform_posix.cc
+++ lib/tsan/rtl/tsan_platform_posix.cc
@@ -54,13 +54,9 @@
 #if !SANITIZER_GO
 void InitializeShadowMemory() {
   // Map memory shadow.
-  uptr shadow =
-      (uptr)MmapFixedNoReserve(ShadowBeg(), ShadowEnd() - ShadowBeg(),
-                               "shadow");
-  if (shadow != ShadowBeg()) {
+  if (!MmapFixedNoReserve(ShadowBeg(), ShadowEnd() - ShadowBeg(), "shadow")) {
     Printf("FATAL: ThreadSanitizer can not mmap the shadow memory\n");
-    Printf("FATAL: Make sure to compile with -fPIE and "
-               "to link with -pie (%p, %p).\n", shadow, ShadowBeg());
+    Printf("FATAL: Make sure to compile with -fPIE and to link with -pie.\n");
     Die();
   }
   // This memory range is used for thread stacks and large user mmaps.
@@ -110,13 +106,11 @@
       (ShadowEnd() - ShadowBeg()) >> 30);
 
   // Map meta shadow.
-  uptr meta_size = MetaShadowEnd() - MetaShadowBeg();
-  uptr meta =
-      (uptr)MmapFixedNoReserve(MetaShadowBeg(), meta_size, "meta shadow");
-  if (meta != MetaShadowBeg()) {
+  const uptr meta = MetaShadowBeg();
+  const uptr meta_size = MetaShadowEnd() - meta;
+  if (!MmapFixedNoReserve(meta, meta_size, "meta shadow")) {
     Printf("FATAL: ThreadSanitizer can not mmap the shadow memory\n");
-    Printf("FATAL: Make sure to compile with -fPIE and "
-               "to link with -pie (%p, %p).\n", meta, MetaShadowBeg());
+    Printf("FATAL: Make sure to compile with -fPIE and to link with -pie.\n");
     Die();
   }
   NoHugePagesInShadow(meta, meta_size);
Index: lib/tsan/rtl/tsan_rtl.cc
===================================================================
--- lib/tsan/rtl/tsan_rtl.cc
+++ lib/tsan/rtl/tsan_rtl.cc
@@ -246,7 +246,8 @@
   const uptr kPageSize = GetPageSizeCached();
   uptr shadow_begin = RoundDownTo((uptr)MemToShadow(addr), kPageSize);
   uptr shadow_end = RoundUpTo((uptr)MemToShadow(addr + size), kPageSize);
-  MmapFixedNoReserve(shadow_begin, shadow_end - shadow_begin, "shadow");
+  if (!MmapFixedNoReserve(shadow_begin, shadow_end - shadow_begin, "shadow"))
+    Die();
 
   // Meta shadow is 2:1, so tread carefully.
   static bool data_mapped = false;
@@ -258,7 +259,8 @@
   if (!data_mapped) {
     // First call maps data+bss.
     data_mapped = true;
-    MmapFixedNoReserve(meta_begin, meta_end - meta_begin, "meta shadow");
+    if (!MmapFixedNoReserve(meta_begin, meta_end - meta_begin, "meta shadow"))
+      Die();
   } else {
     // Mapping continous heap.
     // Windows wants 64K alignment.
@@ -268,7 +270,8 @@
       return;
     if (meta_begin < mapped_meta_end)
       meta_begin = mapped_meta_end;
-    MmapFixedNoReserve(meta_begin, meta_end - meta_begin, "meta shadow");
+    if (!MmapFixedNoReserve(meta_begin, meta_end - meta_begin, "meta shadow"))
+      Die();
     mapped_meta_end = meta_end;
   }
   VPrintf(2, "mapped meta shadow for (%p-%p) at (%p-%p)\n",
@@ -280,10 +283,9 @@
   CHECK_GE(addr, TraceMemBeg());
   CHECK_LE(addr + size, TraceMemEnd());
   CHECK_EQ(addr, addr & ~((64 << 10) - 1));  // windows wants 64K alignment
-  uptr addr1 = (uptr)MmapFixedNoReserve(addr, size, name);
-  if (addr1 != addr) {
-    Printf("FATAL: ThreadSanitizer can not mmap thread trace (%p/%p->%p)\n",
-        addr, size, addr1);
+  if (!MmapFixedNoReserve(addr, size, name)) {
+    Printf("FATAL: ThreadSanitizer can not mmap thread trace (%p/%p)\n",
+        addr, size);
     Die();
   }
 }
@@ -923,7 +925,8 @@
     u64 *p1 = p;
     p = RoundDown(end, kPageSize);
     UnmapOrDie((void*)p1, (uptr)p - (uptr)p1);
-    MmapFixedNoReserve((uptr)p1, (uptr)p - (uptr)p1);
+    if (!MmapFixedNoReserve((uptr)p1, (uptr)p - (uptr)p1))
+      Die();
     // Set the ending.
     while (p < end) {
       *p++ = val;
Index: lib/tsan/rtl/tsan_sync.cc
===================================================================
--- lib/tsan/rtl/tsan_sync.cc
+++ lib/tsan/rtl/tsan_sync.cc
@@ -176,7 +176,8 @@
   uptr metap = (uptr)MemToMeta(p0);
   uptr metasz = sz0 / kMetaRatio;
   UnmapOrDie((void*)metap, metasz);
-  MmapFixedNoReserve(metap, metasz);
+  if (!MmapFixedNoReserve(metap, metasz))
+    Die();
 }
 
 MBlock* MetaMap::GetBlock(uptr p) {