Index: compiler-rt/trunk/lib/esan/esan.h
===================================================================
--- compiler-rt/trunk/lib/esan/esan.h
+++ compiler-rt/trunk/lib/esan/esan.h
@@ -33,6 +33,7 @@
 namespace __esan {
 
 extern bool EsanIsInitialized;
+extern bool EsanDuringInit;
 
 void initializeLibrary(ToolType Tool);
 int finalizeLibrary();
Index: compiler-rt/trunk/lib/esan/esan.cpp
===================================================================
--- compiler-rt/trunk/lib/esan/esan.cpp
+++ compiler-rt/trunk/lib/esan/esan.cpp
@@ -30,6 +30,7 @@
 namespace __esan {
 
 bool EsanIsInitialized;
+bool EsanDuringInit;
 ShadowMapping Mapping;
 
 // Different tools use different scales within the same shadow mapping scheme.
@@ -173,11 +174,13 @@
 }
 
 void initializeLibrary(ToolType Tool) {
-  // We assume there is only one thread during init.
-  if (EsanIsInitialized) {
-    CHECK(Tool == __esan_which_tool);
+  // We assume there is only one thread during init, but we need to
+  // guard against double-init when we're (re-)called from an
+  // early interceptor.
+  if (EsanIsInitialized || EsanDuringInit)
     return;
-  }
+  EsanDuringInit = true;
+  CHECK(Tool == __esan_which_tool);
   SanitizerToolName = "EfficiencySanitizer";
   CacheBinaryName();
   initializeFlags();
@@ -203,6 +206,7 @@
   }
 
   EsanIsInitialized = true;
+  EsanDuringInit = false;
 }
 
 int finalizeLibrary() {
Index: compiler-rt/trunk/lib/esan/esan_interceptors.cpp
===================================================================
--- compiler-rt/trunk/lib/esan/esan_interceptors.cpp
+++ compiler-rt/trunk/lib/esan/esan_interceptors.cpp
@@ -47,10 +47,15 @@
 #define COMMON_INTERCEPT_FUNCTION_VER(name, ver)                          \
   INTERCEPT_FUNCTION_VER(name, ver)
 
+// We must initialize during early interceptors, to support tcmalloc.
+// This means that for some apps we fully initialize prior to
+// __esan_init() being called.
 // We currently do not use ctx.
 #define COMMON_INTERCEPTOR_ENTER(ctx, func, ...)                               \
   do {                                                                         \
     if (UNLIKELY(COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)) {                 \
+      if (!UNLIKELY(EsanDuringInit))                                           \
+        initializeLibrary(__esan_which_tool);                                  \
       return REAL(func)(__VA_ARGS__);                                          \
     }                                                                          \
     ctx = nullptr;                                                             \
@@ -332,6 +337,8 @@
 
 INTERCEPTOR(void *, mmap, void *addr, SIZE_T sz, int prot, int flags,
                  int fd, OFF_T off) {
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, mmap, addr, sz, prot, flags, fd, off);
   if (!fixMmapAddr(&addr, sz, flags))
     return (void *)-1;
   void *result = REAL(mmap)(addr, sz, prot, flags, fd, off);
@@ -341,6 +348,8 @@
 #if SANITIZER_LINUX
 INTERCEPTOR(void *, mmap64, void *addr, SIZE_T sz, int prot, int flags,
                  int fd, OFF64_T off) {
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, mmap64, addr, sz, prot, flags, fd, off);
   if (!fixMmapAddr(&addr, sz, flags))
     return (void *)-1;
   void *result = REAL(mmap64)(addr, sz, prot, flags, fd, off);