File 2021-erts-Add-gcc-compile-error-Werror-undef.patch of Package erlang

From e770c849d011d8d5872e5f1400d77c25a9268186 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Wed, 9 Nov 2016 17:25:25 +0100
Subject: [PATCH 1/3] erts: Add gcc compile error -Werror=undef

to get errors for "#if UNDEFINED_MACRO"
---
 erts/configure.in | 1 +
 1 file changed, 1 insertion(+)

diff --git a/erts/configure.in b/erts/configure.in
index 4bff2eb..fe340b3 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -533,6 +533,7 @@ if test "x$GCC" = xyes; then
   # Treat certain GCC warnings as errors
   LM_TRY_ENABLE_CFLAG([-Werror=return-type], [WERRORFLAGS])
   LM_TRY_ENABLE_CFLAG([-Werror=implicit], [WERRORFLAGS])
+  LM_TRY_ENABLE_CFLAG([-Werror=undef], [WERRORFLAGS])
 
   # until the emulator can handle this, I suggest we turn it off!
   #WFLAGS="-Wall -Wshadow -Wcast-qual -Wmissing-declarations"
-- 
2.10.2