Merge pull request #2870 from acozzette/memcpy-memmove

Ruby: only link against specific version of memcpy if we're using glibc

ruby/ext/google/protobuf_c/wrap_memcpy.c

@@ -30,15 +30,15 @@
 
 #include <string.h>
 
-// On x86-64 Linux, we link against the 2.2.5 version of memcpy so that we
-// avoid depending on the 2.14 version of the symbol. This way, distributions
-// that are using pre-2.14 versions of glibc can successfully use the gem we
-// distribute (https://github.com/google/protobuf/issues/2783).
+// On x86-64 Linux with glibc, we link against the 2.2.5 version of memcpy so
+// that we avoid depending on the 2.14 version of the symbol. This way,
+// distributions that are using pre-2.14 versions of glibc can successfully use
+// the gem we distribute (https://github.com/google/protobuf/issues/2783).
 //
 // This wrapper is enabled by passing the linker flags -Wl,-wrap,memcpy in
 // extconf.rb.
 #ifdef __linux__
-#ifdef __x86_64__
+#if defined(__x86_64__) && defined(__GNU_LIBRARY__)
 __asm__(".symver memcpy,memcpy@GLIBC_2.2.5");
 void *__wrap_memcpy(void *dest, const void *src, size_t n) {
     return memcpy(dest, src, n);