From 896b248c8ccea44ba52a99e2f18b6886a1a9c8d4 Mon Sep 17 00:00:00 2001
From: David Chisnall <David.Chisnall@microsoft.com>
Date: Fri, 5 Jul 2019 09:16:08 +0100
Subject: [PATCH] Fix undefined behaviour in FreeBSD PAL.

We were passing an argument less than 4K to the MAP_ALIGNED macro, which
caused an undefined shift.  The compiler helpfully propagated the undef
values back to earlier in the code and gave us some exciting nonsense.
---
 src/pal/pal_freebsd.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/src/pal/pal_freebsd.h b/src/pal/pal_freebsd.h
index 9f3725b..8487f19 100644
--- a/src/pal/pal_freebsd.h
+++ b/src/pal/pal_freebsd.h
@@ -77,10 +77,7 @@ namespace snmalloc
       // Alignment must be a power of 2.
       assert(align == bits::next_pow2(align));
 
-      if (align == 0)
-      {
-        align = 1;
-      }
+      align = bits::max<size_t>(4096, align);
 
       size_t log2align = bits::next_pow2_bits(align);