Add reallocarray(3).

Originally a BSD extension, now in glibc too. We've used it internally
for a while.

(cherry-pick of e4b13f7e3ca68edfcc5faedc5e7d4e13c4e8edb9.)

Bug: http://b/112163459
Test: ran tests
Change-Id: I813c3a62b13ddb91ba41e32a5a853d09207ea6bc
Merged-In: I813c3a62b13ddb91ba41e32a5a853d09207ea6bc

1 files changed, 9 insertions, 1 deletions

diff --git a/linker/linker_memory.cpp b/linker/linker_memory.cpp
index 6a54c138f..f2cce01d9 100644
--- a/linker/linker_memory.cpp
+++ b/linker/linker_memory.cpp
@@ -80,7 +80,15 @@ void* realloc(void* p, size_t byte_count) {
   return get_allocator().realloc(p, byte_count);
 }
 
+void* reallocarray(void* p, size_t item_count, size_t item_size) {
+  size_t byte_count;
+  if (__builtin_mul_overflow(item_count, item_size, &byte_count)) {
+    errno = ENOMEM;
+    return nullptr;
+  }
+  return get_allocator().realloc(p, byte_count);
+}
+
 void free(void* ptr) {
   get_allocator().free(ptr);
 }
-