From 9b8fe84ece6844c0863fc300bb714efc0f179c1a Mon Sep 17 00:00:00 2001
From: Ryan Northey <ryan@synca.io>
Date: Fri, 12 Dec 2025 12:54:10 +0000
Subject: [PATCH] build: Pass env CFLAGS through to make

In our (envoy) build we use a sysroot to ensure hermetic builds.

This fixes a problem where configure is passed the sysroot flag and
detects kernel headers for openat2.h but then make doesnt have the sysroot
and fails.

Signed-off-by: Ryan Northey <ryan@synca.io>
---
 configure    | 6 ++++--
 src/Makefile | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 848aa7bd2..81d58760e 100755
--- a/configure
+++ b/configure
@@ -120,8 +120,9 @@ print_config() {
 }
 
 # Default CFLAGS
-CFLAGS="-D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -include config-host.h"
-BUILD_CFLAGS=""
+ENV_CFLAGS="${CFLAGS}"
+CFLAGS="${CFLAGS:+$CFLAGS }-D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -include config-host.h"
+BUILD_CFLAGS="${ENV_CFLAGS}"
 
 # Print configure header at the top of $config_host_h
 echo "/*" > $config_host_h
@@ -588,6 +589,7 @@ fi
 echo "CC=$cc" >> $config_host_mak
 print_config "CC" "$cc"
 echo "CXX=$cxx" >> $config_host_mak
+echo "BUILD_CFLAGS=$BUILD_CFLAGS" >> $config_host_mak
 print_config "CXX" "$cxx"
 
 # generate io_uring_version.h
diff --git a/src/Makefile b/src/Makefile
index 42e18773f..7febcf3c2 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -13,6 +13,7 @@ override CPPFLAGS += -D_GNU_SOURCE \
 CFLAGS ?= -O3 -Wall -Wextra -fno-stack-protector
 override CFLAGS += -Wno-unused-parameter \
 	-DLIBURING_INTERNAL \
+	$(BUILD_CFLAGS) \
 	$(LIBURING_CFLAGS)
 SO_CFLAGS=-fPIC $(CFLAGS)
 L_CFLAGS=$(CFLAGS)