https://git.ruby-lang.org/ruby.git/commit/?id=b1b385465e

From b1b385465e4fc1cab84b2a3fa112a33a3e5ab076 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@r...>
Date: Fri, 17 May 2019 10:25:34 +0900
Subject: Do not call memcpy if copying nothing

c.f.
* e7b18ca6d9b45b7e71694557b9fab8152c62c1ed
* 34e1079aef81d108890fb167d7df69960e994ff5

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index c73fd63..0c6d7e3 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1749,6 +1749,15 @@ rb_alloc_tmp_buffer2(volatile VALUE *store, long count, size_t elsize) https://github.com/ruby/ruby/blob/trunk/include/ruby/ruby.h#L1749
 #define MEMCPY(p1,p2,type,n) memcpy((p1), (p2), sizeof(type)*(size_t)(n))
 #define MEMMOVE(p1,p2,type,n) memmove((p1), (p2), sizeof(type)*(size_t)(n))
 #define MEMCMP(p1,p2,type,n) memcmp((p1), (p2), sizeof(type)*(size_t)(n))
+#ifdef __GLIBC__
+static inline void *
+ruby_nonempty_memcpy(void *dest, const void *src, size_t n)
+{
+    /* if nothing to be copied, src may be NULL */
+    return (n ? memcpy(dest, src, n) : dest);
+}
+#define memcpy(p1,p2,n) ruby_nonempty_memcpy(p1, p2, n)
+#endif
 
 void rb_obj_infect(VALUE victim, VALUE carrier);
 
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