[PATCH] D63668: [Support] Improve zero-size allocation with safe_malloc, etc.

[Andus Yu via Phabricator via llvm-commits]

andusy created this revision.
andusy added reviewers: hubert.reinterpretcast, xingxue, jasonliu.
andusy added a project: LLVM.
Herald added a subscriber: jsji.

The current implementations of the memory allocation functions mistake a `nullptr` returned from `std::malloc`, `std::calloc`, or `std::realloc` as a failure. The behaviour for each of `std::malloc`, `std::calloc`, and `std::realloc` when the size is 0 is implementation defined, and may return a `nullptr`.

If the system function returns `nullptr`, check if the size is 0 and return a non-null pointer using malloc.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D63668

Files:
  llvm/include/llvm/Support/MemAlloc.h


Index: llvm/include/llvm/Support/MemAlloc.h
===================================================================
--- llvm/include/llvm/Support/MemAlloc.h
+++ llvm/include/llvm/Support/MemAlloc.h
@@ -24,23 +24,32 @@
 
 LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_malloc(size_t Sz) {
   void *Result = std::malloc(Sz);
-  if (Result == nullptr)
+  if (Result == nullptr) {
+    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) {
+    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) {
+    if (Sz == 0)
+      return safe_malloc(1);
     report_bad_alloc_error("Allocation failed");
+  }
   return Result;
 }
 


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