From 610b9ea269b6875c7ca990a7b69e5e949606ddf7 Mon Sep 17 00:00:00 2001
From: Chris Kleeschulte <chrisk@bitpay.com>
Date: Wed, 10 Feb 2016 17:18:08 -0500
Subject: [PATCH] Added a doc fragment in build.md about cross compilation and
 clarified the error message.

---
 bin/variables.sh |  2 +-
 docs/build.md    | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/bin/variables.sh b/bin/variables.sh
index 21b962ed..0988e0fa 100755
--- a/bin/variables.sh
+++ b/bin/variables.sh
@@ -25,7 +25,7 @@ get_host_and_platform () {
         arch="${SYS[0]}"
         platform="${SYS[1]}"-"${SYS[2]}"
       else
-        error_message="You've specified a cross compiler, but we could not compute the host-platform-triplet for cross compilation. Please set CC and CXX environment variables with host-platform-triplet-*. Example: CC=arm-linux-gnueabihf-gcc CXX=arm-linux-gnueabihf-g++"
+        error_message="You've specified a cross compiler, but we could not compute the host-platform-triplet for cross compilation. Please set CC and CXX environment variables with host-platform-triplet-*. Also ensure the cross compiler exists on your system and is available on your path. Example: CC=arm-linux-gnueabihf-gcc CXX=arm-linux-gnueabihf-g++"
         return_error_message
       fi
     fi
diff --git a/docs/build.md b/docs/build.md
index 1846356f..d22b8411 100644
--- a/docs/build.md
+++ b/docs/build.md
@@ -80,6 +80,34 @@ And finally run the build which will take several minutes. A script in the "bin"
 npm install
 ```
 
+## Cross Compilation
+If you desire to cross compile to ARM or Windows from a system that has cross compilation tools available for use, please use the following directions:
+
+Using a Debian (Jessie) system as the host system (the system that will be doing the compiling):
+
+```bash
+echo -n "deb http://emdebian.org/tools/debian/ jessie main" | sudo tee -a /etc/apt/sources.list
+sudo dpkg --add-architecture armhf  #or whatever arch you are interested in compiling for
+sudo apt-get update #you will get GPG KEY warnings, you can decide if you would like to trust the key
+sudo apt-get install crossbuild-essential-armhf
+```
+
+Next is to use the cross compilation toolchain instead of the defaults:
+
+```bash
+CXX=arm-linux-gnueabihf-g++ CC=arm-linux-gnueabihf-gcc npm install
+```
+
+The only thing different is the setting of CC/CXX environment variables. Please make sure those compilers (arm-linux-gnueabihf-gcc) actually exist and are on your path.
+
+```bash
+arm-linux-gnueabihf-g++ -v
+arm-linux-gnueabihf-gcc -v
+```
+
+You should get output with the last line ending with something like this:
+gcc version 4.9.2 ( 4.9.2-10)
+
 Once everything is built, you can run bitcore-node via:
 
 ```bash