From 49901079d4567e58fe8c143909d121ec354c87f0 Mon Sep 17 00:00:00 2001
From: Alexander Egorenkov <egorenar@linux.ibm.com>
Date: Thu, 24 Jun 2021 10:04:10 +0200
Subject: [PATCH] common.mak: Introduce user-defined function
 check_header_prereq()
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The new user-defined function allows to check for C headers in
make's conditional statements.

Example:

ifeq ($(call check_header_prereq,"systemd/sd-daemon.h"),yes)
  $(warning "systemd support enabled")
else
  $(warning "systemd support disabled")
endif

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Acked-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
---
 common.mak | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/common.mak b/common.mak
index e6fd2778..8ddb571a 100644
--- a/common.mak
+++ b/common.mak
@@ -111,6 +111,20 @@ ifeq ("${ASAN}","1")
 	DEFAULT_LDFLAGS += -fsanitize=address
 endif
 
+#
+# Check for header prerequisite
+#
+# $1: Name of include file to check
+# $2: Additional compiler & linker options (optional)
+#
+# Returns "yes" on success and nothing otherwise
+#
+define check_header_prereq
+$(shell printf "#include <%s>\n int main(void) {return 0;}" $1 | \
+        ( $(CC) $(filter-out --coverage, $(ALL_CFLAGS)) $(ALL_CPPFLAGS) \
+                $2 -o /dev/null -xc - ) >/dev/null 2>&1 && echo -n yes)
+endef
+
 #
 # Check for build dependency
 #