build: move GOOS, GOARCH, GOROOT lookup into central library.

bake default values in during build.

R=r
CC=golang-dev
http://codereview.appspot.com/186173

2 files changed, 39 insertions, 0 deletions

diff --git a/src/lib9/Makefile b/src/lib9/Makefile
index 9038730b1..592bc3b1a 100644
--- a/src/lib9/Makefile
+++ b/src/lib9/Makefile
@@ -69,6 +69,7 @@ LIB9OFILES=\
 	getenv.$O\
 	getfields.$O\
 	getwd.$O\
+	goos.$O\
 	main.$O\
 	nan.$O\
 	nulldir.$O\
@@ -115,6 +116,9 @@ $(LIB): $(OFILES)
 %.$O: utf/%.c
 	$(CC) -c $(CFLAGS) $<
 
+goos.$O: goos.c
+	$(CC) -c $(CFLAGS) -DGOOS='"$(GOOS)"' -DGOARCH='"$(GOARCH)"' -DGOROOT='"$(GOROOT)"' $<
+
 clean:
 	rm -f *.$O *.6 6.out $(LIB)
 
diff --git a/src/lib9/goos.c b/src/lib9/goos.c
new file mode 100644
index 000000000..668dc1941
--- /dev/null
+++ b/src/lib9/goos.c
@@ -0,0 +1,35 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include <u.h>
+#include <libc.h>
+
+static char*
+defgetenv(char *name, char *def)
+{
+	char *p;
+	
+	p = getenv(name);
+	if(p == nil || p[0] == '\0')
+		p = def;
+	return p;
+}
+
+char*
+getgoos(void)
+{
+	return defgetenv("GOOS", GOOS);
+}
+
+char*
+getgoarch(void)
+{
+	return defgetenv("GOARCH", GOARCH);
+}
+
+char*
+getgoroot(void)
+{
+	return defgetenv("GOROOT", GOROOT);
+}