Index: lib/Fuzzer/FuzzerExtFunctionsWeak.cpp
===================================================================
--- lib/Fuzzer/FuzzerExtFunctionsWeak.cpp
+++ lib/Fuzzer/FuzzerExtFunctionsWeak.cpp
@@ -41,7 +41,8 @@
 ExternalFunctions::ExternalFunctions() {
 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)                            \
   this->NAME = ::NAME;                                                         \
-  CheckFnPtr((void *)::NAME, #NAME, WARN);
+  CheckFnPtr(reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(::NAME)),    \
+             #NAME, WARN);
 
 #include "FuzzerExtFunctions.def"