diff --git a/llvm/include/llvm/Support/MemAlloc.h b/llvm/include/llvm/Support/MemAlloc.h
--- a/llvm/include/llvm/Support/MemAlloc.h
+++ b/llvm/include/llvm/Support/MemAlloc.h
@@ -24,23 +24,41 @@
 
 LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_malloc(size_t Sz) {
   void *Result = std::malloc(Sz);
-  if (Result == nullptr)
+  if (Result == nullptr) {
+    // It is implementation-defined whether allocation occurs if the space
+    // requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
+    // non-zero, if the space requested was zero.
+    if (Sz == 0)
+      return safe_malloc(1);
     report_bad_alloc_error("Allocation failed");
+  }
   return Result;
 }
 
 LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_calloc(size_t Count,
                                                         size_t Sz) {
   void *Result = std::calloc(Count, Sz);
-  if (Result == nullptr)
+  if (Result == nullptr) {
+    // It is implementation-defined whether allocation occurs if the space
+    // requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
+    // non-zero, if the space requested was zero.
+    if (Count == 0 || Sz == 0)
+      return safe_malloc(1);
     report_bad_alloc_error("Allocation failed");
+  }
   return Result;
 }
 
 LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_realloc(void *Ptr, size_t Sz) {
   void *Result = std::realloc(Ptr, Sz);
-  if (Result == nullptr)
+  if (Result == nullptr) {
+    // It is implementation-defined whether allocation occurs if the space
+    // requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
+    // non-zero, if the space requested was zero.
+    if (Sz == 0)
+      return safe_malloc(1);
     report_bad_alloc_error("Allocation failed");
+  }
   return Result;
 }