From b4f3eb0637df31602df515b32b445acbf0039703 Mon Sep 17 00:00:00 2001
From: Calascibetta Romain <romain.calascibetta@gmail.com>
Date: Wed, 26 Feb 2020 11:38:55 +0100
Subject: [PATCH] Fix getrandom on Ubuntu 16.04 (GLIBC 2.23) (#14)

* use system call SYS_getrandom
* Add Ubuntu 16.04 to Travis CI script
---
 .travis.yml                   |  2 ++
 rng/unix/mc_getrandom_stubs.c | 12 +++++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 1d308afd..151c6a1e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,5 +11,7 @@ matrix:
   include:
   - os: osx
     env: OCAML_VERSION=4.08
+  - dist: xenial
+    env: OCAML_VERSION=4.08
 notifications:
   email: false
diff --git a/rng/unix/mc_getrandom_stubs.c b/rng/unix/mc_getrandom_stubs.c
index fc8b7413..88bc9019 100644
--- a/rng/unix/mc_getrandom_stubs.c
+++ b/rng/unix/mc_getrandom_stubs.c
@@ -6,9 +6,16 @@
 #include <caml/bigarray.h>
 
 #if defined(__linux)
+# include <errno.h>
 // on Linux, we use getrandom and loop
-#include <sys/random.h>
-#include <errno.h>
+
+# if __GLIBC__ && __GLIBC__ <= 2 && __GLIBC_MINOR__ < 25
+# include <sys/syscall.h>
+# define getrandom(buf, len, flags) syscall(SYS_getrandom, (buf), (len), (flags))
+# else
+# include <sys/random.h>
+# define getrandom(buf, len, flags) getrandom((buf), (len), (flags))
+# endif
 
 void raw_getrandom (uint8_t *data, uint32_t len) {
   int r, off = 0;
@@ -19,7 +26,6 @@ void raw_getrandom (uint8_t *data, uint32_t len) {
     off += r;
   }
 }
-
 #elif (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__APPLE__))
 // on BSD and macOS, loop (in pieces of 256) getentropy
 #if defined(__APPLE__)