From 26e34cd6f2471f04ba097001a215caed12a8574a Mon Sep 17 00:00:00 2001
From: John Whittington <git@jbrengineering.co.uk>
Date: Tue, 4 Aug 2020 11:51:35 +0200
Subject: [PATCH] detect and use GNU grep on macOS

---
 Common.mk | 13 +++++++++++--
 Sam.mk    |  2 +-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Common.mk b/Common.mk
index 0c1f92c..27d2135 100644
--- a/Common.mk
+++ b/Common.mk
@@ -8,8 +8,8 @@ dir_if_exists = $(if $(wildcard $(1)$(2)),$(1))
 # result = $(call READ_BOARD_TXT, 'boardname', 'parameter')
 PARSE_BOARD = $(shell if [ -f $(BOARDS_TXT) ]; \
 then \
-  grep -Ev '^\#' $(BOARDS_TXT) | \
-  grep -E "^[ \t]*$(1).$(2)=" | \
+  $(GREP) -Ev '^\#' $(BOARDS_TXT) | \
+  $(GREP) -E "^[ \t]*$(1).$(2)=" | \
   cut -d = -f 2- | \
   cut -d : -f 2; \
 fi)
@@ -45,15 +45,24 @@ $(call arduino_output,$(call ardmk_include) Configuration:)
 ########################################################################
 #
 # Detect OS
+
 ifeq ($(OS),Windows_NT)
     CURRENT_OS = WINDOWS
+    GREP := grep
 else
     UNAME_S := $(shell uname -s)
     ifeq ($(UNAME_S),Linux)
         CURRENT_OS = LINUX
+        GREP := grep
     endif
     ifeq ($(UNAME_S),Darwin)
         CURRENT_OS = MAC
+        ifeq (, $(shell which ggrep))
+            echo $(info Using macOS BSD grep, please install GNU grep to avoid warnings)
+            GREP := grep
+        else
+            GREP := ggrep
+        endif
     endif
 endif
 $(call show_config_variable,CURRENT_OS,[AUTODETECTED])
diff --git a/Sam.mk b/Sam.mk
index 7f3cd2b..f11554f 100644
--- a/Sam.mk
+++ b/Sam.mk
@@ -404,7 +404,7 @@ CFLAGS_STD += -std=gnu11
 CPPFLAGS += -DMD -D$(USB_TYPE) '-DUSB_PRODUCT=$(USB_PRODUCT)' '-DUSB_MANUFACTURER=$(USB_MANUFACTURER)'
 
 # Get extra define flags from boards.txt
-EXFLAGS := $(shell echo $(call PARSE_BOARD,$(BOARD_TAG),build.extra_flags) | grep -oE '(-D)\w+')
+EXFLAGS := $(shell echo $(call PARSE_BOARD,$(BOARD_TAG),build.extra_flags) | $(GREP) -oE '(-D)\w+')
 
 # Strip only defines from extra flags as boards file appends user {build.usb}
 CPPFLAGS += $(EXFLAGS)