From a0bd410d67e0632526ba3eb891791c6753b51374 Mon Sep 17 00:00:00 2001
From: Guillem Jover <guillem@hadrons.org>
Date: Sun, 12 Apr 2020 04:01:27 +0200
Subject: [PATCH] build: Honor user build flags
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CPPFLAGS, CFLAGS and LDFLAGS are user flags, which we need to preserve,
regardless of the user passing them over the environment or the
command-line. Any required flag that the build system needs, has to be
set in some other flag (which we will namespace with «MK_») so that the
build will use even if the user flags are passed, even though the user
should be able to override by appending after them. We pass CPPFLAGS to
any compilation command that missed them.

Signed-off-by: Guillem Jover <guillem@hadrons.org>
---
 harness/Makefile |    9 ++++++---
 src/Makefile     |   18 +++++++++---------
 2 files changed, 15 insertions(+), 12 deletions(-)

--- a/harness/Makefile
+++ b/harness/Makefile
@@ -6,13 +6,16 @@ PROGS:=$(PARTPROGS) $(EXTRAPROGS)
 HARNESS_SRCS:=main.c
 # io_queue.c
 
-CFLAGS+=-Wall -I../src -g -O2
+MK_CPPFLAGS = -I../src $(CPPFLAGS)
+CFLAGS ?= -Wall -g -O2
+MK_CFLAGS = $(CFLAGS)
 #-lpthread -lrt
+MK_LDFLAGS = main.c $(LIBAIO) -lpthread $(LDFLAGS)
 
 # gcc-11 does not like the test case in 3.t that
 # passes an invalid pointer (-1) to the kernel, so
 # tell the compiler we do not need a warning here
-cases/3.p:	CFLAGS+=-Wno-stringop-overflow
+cases/3.p:	MK_CFLAGS+=-Wno-stringop-overflow
 
 # Change this on the build line to run tests against the installed libraries:
 # make LIBAIO=-laio partcheck
@@ -21,7 +24,7 @@ LIBAIO?=../src/libaio.a
 all: $(PROGS)
 
 $(PROGS): %.p: %.t $(HARNESS_SRCS)
-	$(CC) $(CFLAGS) -DTEST_NAME=\"$<\" -o $@ main.c $(LIBAIO) -lpthread
+	$(CC) $(MK_CPPFLAGS) $(MK_CFLAGS) -DTEST_NAME=\"$<\" -o $@ $(MK_LDFLAGS)
 
 clean:
 	rm -f $(PROGS) *.o runtests.out rofile wofile rwfile
--- a/src/Makefile
+++ b/src/Makefile
@@ -3,12 +3,12 @@ prefix=/usr
 includedir=$(prefix)/include
 libdir=$(prefix)/lib
 
-CFLAGS ?= -g -fomit-frame-pointer -O2
-CFLAGS += -Wall -I. -fPIC
-SO_CFLAGS=-shared $(CFLAGS)
-L_CFLAGS=$(CFLAGS)
-LINK_FLAGS=
-LINK_FLAGS+=$(LDFLAGS)
+MK_CPPFLAGS = -I. $(CPPFLAGS)
+CFLAGS ?= -Wall -g -fomit-frame-pointer -O2
+MK_CFLAGS = -fPIC $(CFLAGS)
+SO_CFLAGS = -shared $(MK_CFLAGS)
+L_CFLAGS = $(MK_CFLAGS)
+MK_LDFLAGS = $(LDFLAGS)
 ENABLE_SHARED ?= 1
 
 soname=libaio.so.1
@@ -43,10 +43,10 @@ libaio_sobjs := $(patsubst %.c,%.os,$(li
 $(libaio_objs) $(libaio_sobjs): libaio.h vsys_def.h
 
 %.os: %.c
-	$(CC) $(SO_CFLAGS) -c -o $@ $<
+	$(CC) $(MK_CPPFLAGS) $(SO_CFLAGS) -c -o $@ $<
 
 %.ol: %.c
-	$(CC) $(L_CFLAGS) -c -o $@ $<
+	$(CC) $(MK_CPPFLAGS) $(L_CFLAGS) -c -o $@ $<
 
 AR ?= ar
 RANLIB ?= ranlib
@@ -56,7 +56,7 @@ libaio.a: $(libaio_objs)
 
 $(libname): $(libaio_sobjs) libaio.map
 	$(CC) $(CFLAGS) -c struct_offsets.c
-	$(CC) $(SO_CFLAGS) -Wl,--version-script=libaio.map -Wl,-soname=$(soname) -o $@ $(libaio_sobjs) $(LINK_FLAGS)
+	$(CC) $(SO_CFLAGS) -Wl,--version-script=libaio.map -Wl,-soname=$(soname) -o $@ $(libaio_sobjs) $(MK_LDFLAGS)
 
 install: $(all_targets)
 	install -d -m 755 $(includedir)