include/u.h: define _DEFAULT_SOURCE for new glibc

glibc devs have apparently decided _BSD_SOURCE will be
deprecated on Linux, and issue a preprocessor warning if
declaring _BSD_SOURCE without _DEFAULT_SOURCE.

https://sourceware.org/glibc/wiki/Release/2.20

Fixes #8397.

LGTM=iant
R=dave, gobot, iant
CC=golang-codereviews
https://golang.org/cl/112530043

diff --git a/include/u.h b/include/u.h
index 6b2d50cc1f97143f22edeeebcaa138f1768aba7b..489b2a3886b568c6e848b8bb110fb2f6adfed1e4 100644 (file)
--- a/include/u.h
+++ b/include/u.h
@@ -40,6 +40,7 @@ extern "C" {
 #endif
 #define _BSD_SOURCE 1
 #define _NETBSD_SOURCE 1       /* NetBSD */
+#define _DEFAULT_SOURCE 1      /* glibc > 2.19 */
 #define _SVID_SOURCE 1
 #if !defined(__APPLE__) && !defined(__OpenBSD__)
 #      define _XOPEN_SOURCE 1000