From 693606fa807c30ce4c0ce25e2fa852210533b19f Mon Sep 17 00:00:00 2001
From: Matthew Jaffee <jaffee@Matthews-MacBook-Pro.local>
Date: Tue, 10 Aug 2021 14:01:53 -0500
Subject: [PATCH] better explanation for 'cannot allocate memory' error

---
 syswrap/mmap.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/syswrap/mmap.go b/syswrap/mmap.go
index 238f6dd6f..2d89ce39b 100644
--- a/syswrap/mmap.go
+++ b/syswrap/mmap.go
@@ -20,6 +20,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"syscall"
+	"strings"
 
 	"github.com/pkg/errors"
 )
@@ -56,6 +57,9 @@ func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, e
 	data, err = syscall.Mmap(fd, offset, length, prot, flags)
 	if err != nil {
 		atomic.AddUint64(&mapCount, ^uint64(0)) // decrement
+		if strings.Contains(err.Error(), "cannot allocate memory") {
+			err = errors.New("mmap 'cannot allocate memory' — please see the troubleshooting how-to in the FeatureBase docs.")
+		}
 	}
 	return data, err
 }