Expanded comment in binding.gyp
diff --git a/binding.gyp b/binding.gyp
index b775113..ed7fc75 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -44,6 +44,10 @@
'target_defaults': {
# Emperically, Node only exports ALPN symbols if its major version is >0.
# io.js always reports versions >0 and always exports ALPN symbols.
+ # Therefore, Node's major version will be truthy if and only if it
+ # supports ALPN. The output of "node -v" is v[major].[minor].[patch],
+ # like "v4.1.1" in a recent version. We use grep to extract just the
+ # major version. "4", would be the output for the example.
'defines': [
'TSI_OPENSSL_ALPN_SUPPORT=<!(node -v | grep -oP "(?<=v)(\d+)(?=\.\d+\.\d+)")'
],