From 6ce739f01ff7f0c51081eb2e4598b33fafe3486b Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 30 Apr 2018 18:19:37 +0200
Subject: libwg-go: use system Go when possible

We're still maybe curlzipping and using a binary distribution of Go, but
at least this is only the case on machines that don't have go.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 app/tools/libwg-go/Makefile | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/app/tools/libwg-go/Makefile b/app/tools/libwg-go/Makefile
index 43af1439..d931c056 100644
--- a/app/tools/libwg-go/Makefile
+++ b/app/tools/libwg-go/Makefile
@@ -10,8 +10,6 @@ NDK_GO_ARCH_MAP_mips := mipsx
 NDK_GO_ARCH_MAP_mips64 := mips64x
 
 export GOPATH := $(CURDIR)/gopath
-export GOROOT := $(CURDIR)/goroot
-export PATH := $(GOROOT)/bin:$(PATH)
 CLANG_FLAGS := --target=$(ANDROID_LLVM_TRIPLE) --gcc-toolchain=$(ANDROID_TOOLCHAIN_ROOT) --sysroot=$(ANDROID_SYSROOT)
 export CGO_CFLAGS := $(CLANG_FLAGS) $(CFLAGS)
 export CGO_LDFLAGS := $(CLANG_FLAGS) $(LDFLAGS)
@@ -20,20 +18,32 @@ export GOARCH := $(NDK_GO_ARCH_MAP_$(ANDROID_ARCH_NAME))
 export GOOS := android
 export CGO_ENABLED := 1
 
-GORELEASEVERSION := 1.10.1
-GORELEASETARBALL := https://dl.google.com/go/go$(GORELEASEVERSION).$(shell uname -s | tr '[:upper:]' '[:lower:]')-$(NDK_GO_ARCH_MAP_$(shell uname -m)).tar.gz
-
 default: $(DESTDIR)/libwg-go.so
 
+GOBUILDARCH := $(NDK_GO_ARCH_MAP_$(shell uname -m))
+GOBUILDOS := $(shell uname -s | tr '[:upper:]' '[:lower:]')
+GOBUILDVERSION := 1.10.1
+GOBUILDTARBALL := https://dl.google.com/go/go$(GOBUILDVERSION).$(GOBUILDOS)-$(GOBUILDARCH).tar.gz
+
+ifeq (go version go$(GOBUILDVERSION) $(GOBUILDOS)/$(GOBUILDARCH),$(shell go version 2>/dev/null))
+ensure_go_exists:
+	@echo "Using system go"
+else
+export GOROOT := $(CURDIR)/goroot
+export PATH := $(GOROOT)/bin:$(PATH)
 $(GOROOT)/bin/go:
 	rm -rf "$(GOROOT)"
 	mkdir -p "$(GOROOT)"
-	curl "$(GORELEASETARBALL)" | tar -C "$(GOROOT)" --strip-components=1 -xzf - || rm -rf "$(GOROOT)"
+	curl "$(GOBUILDTARBALL)" | tar -C "$(GOROOT)" --strip-components=1 -xzf - || rm -rf "$(GOROOT)"
+ensure_go_exists: $(GOROOT)/bin/go
+endif
 
-$(DESTDIR)/libwg-go.so: $(FILES) api-android.go jni.c $(GOROOT)/bin/go
+$(DESTDIR)/libwg-go.so: $(FILES) api-android.go jni.c ensure_go_exists
 	find . -name '*.go' -type l -delete
 	find . -type d -empty -delete
 	mkdir -p $(subst ../wireguard-go/,./,$(dir $(FILES)))
 	$(foreach FILE,$(FILES),ln -sfrt $(subst ../wireguard-go/,./,$(dir $(FILE))) $(FILE);)
 	go get -v -d
 	go build -v -o $(DESTDIR)/libwg-go.so -buildmode c-shared
+
+.PHONY: ensure_go_exists
-- 
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