From 24eff2112b7016ef73ada178d8102a3b432f1f03 Mon Sep 17 00:00:00 2001
From: Christophe de Dinechin <dinechin@redhat.com>
Date: Fri, 24 Nov 2017 10:43:30 +0100
Subject: [PATCH] Workaround a bug in GNU make when reloading generated
 makefiles

The problem was discovered testing parallel builds.
The configuration rules depend on generated pkg-config.mk files.
However, experimentally, variables set in these files are not
correctly reloaded in rules declared in other variables.

Specifically, $(CFLAGS_PKGCONFIG) was not re-expanded after being
modified, which led to configuration builds to lack the required
flags, causing false configuration step failures.

The flags are now explicitly listed using $(shell cat...), which
is a little bit more expensive during the configuration step, but
ensures that the flags are correctly seen. Note that at that stage,
the dependency ensures that all the files were built correctly.
---
 config.gnu.mk | 10 ++++++----
 rules.mk      | 28 ++++++++++++++++++----------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/config.gnu.mk b/config.gnu.mk
index 23bbf7b..d9bb387 100644
--- a/config.gnu.mk
+++ b/config.gnu.mk
@@ -113,11 +113,13 @@ CFG_TEST=								\
 CFG_UNDEF0=								\
 	| sed -e 's|^\#define \(.*\) 0$$|/* \#undef \1 */|g' > "$@";	\
 	[ -f "$<".out ] && cat >> "$@" "$<".out; true
+CFG_CFLAGS=	$(CFLAGS)   $(shell cat $(PKG_CFLAGS) $(PKG_LDFLAGS) /dev/null)
+CFG_CXXFLAGS=	$(CXXFLAGS) $(shell cat $(PKG_CFLAGS) $(PKG_LDFLAGS) /dev/null)
 
-CFG_CC_CMD=	$$($(CC)  $(CFLAGS)   $(CFLAGS_CONFIG_$*)   $(LDFLAGS)      $(CFG_TEST))
-CFG_CXX_CMD=	$$($(CXX) $(CXXFLAGS) $(CXXFLAGS_CONFIG_$*) $(LDFLAGS)      $(CFG_TEST))
-CFG_LIB_CMD=	$$($(CC)  $(CFLAGS)   $(CFLAGS_CONFIG_$*)   $(LDFLAGS) -l$* $(CFG_TEST))
-CFG_FN_CMD=	$$($(CC)  $(CFLAGS)   $(CFLAGS_CONFIG_$*)   $(LDFLAGS)      $(CFG_TEST))
+CFG_CC_CMD=	`$(CC)  $(CFG_CFLAGS)   $(CFLAGS_CONFIG_$*)        $(CFG_TEST)`
+CFG_CXX_CMD=	`$(CXX) $(CFG_CXXFLAGS) $(CXXFLAGS_CONFIG_$*)      $(CFG_TEST)`
+CFG_LIB_CMD=	`$(CC)  $(CFG_CFLAGS)   $(CFLAGS_CONFIG_$*)   -l$* $(CFG_TEST)`
+CFG_FN_CMD=	`$(CC)  $(CFG_CFLAGS)   $(CFLAGS_CONFIG_$*)        $(CFG_TEST)`
 
 CC_CONFIG=	$(CFG_DEF) HAVE_$(CFG_UPPER)_H  $(CFG_CC_CMD)  $(CFG_UNDEF0)
 CXX_CONFIG=	$(CFG_DEF) HAVE_$(CFG_UPPER)    $(CFG_CXX_CMD) $(CFG_UNDEF0)
diff --git a/rules.mk b/rules.mk
index 7cfcd58..f5315af 100644
--- a/rules.mk
+++ b/rules.mk
@@ -94,9 +94,6 @@ BUILD_COUNT:=   $(words $(SOURCES))
 GIT_REVISION:=  $(shell git rev-parse --short HEAD 2> /dev/null || echo "unknown")
 PROFILE_OUTPUT:=$(subst $(EXE_EXT),,$(OBJROOT_EXE))_prof_$(GIT_REVISION).vsp
 
--include $(PKGCONFIGS:%=$(OBJROOT)/%.pkg-config.mk)
-
-
 #------------------------------------------------------------------------------
 #   User targets
 #------------------------------------------------------------------------------
@@ -182,7 +179,6 @@ objects:$(OBJDIR:%=%/.mkdir) $(OBJECTS)
 
 # "Hooks" for pre and post build steps
 config: $(VARIANTS:%=%.variant)
-config: $(PKGCONFIGS:%=$(OBJROOT)/%.pkg-config.mk)
 config: $(CONFIG:%=config.h)
 prebuild: config
 postbuild:
@@ -209,11 +205,6 @@ product.test: product .ALWAYS
 %.install_hdr: $(PREFIX_HDR).mkdir
 	$(PRINT_INSTALL) $(INSTALL) $* $(PREFIX_HDR)
 
-# Check pkg-config
-$(OBJROOT)/%.pkg-config.mk: $(MAKEFILE_DEPS) $(OBJROOT)/.mkdir
-	$(PRINT_PKGCONFIG) pkg-config $*
-	$(PRINT_COMMAND)  (echo CFLAGS_PKGCONFIG+=`pkg-config --cflags $*` && echo LDFLAGS_PKGCONFIG+=`pkg-config --libs $*`) > $@
-
 # Benchmarking (always done with profile target)
 benchmark:	$(BENCHMARK:%=%.benchmark) $(BENCHMARKS:%=%.benchmark)
 product.benchmark: product .ALWAYS
@@ -391,6 +382,23 @@ ifeq ($(MAKECMDGOALS),build)
 endif
 
 
+#------------------------------------------------------------------------------
+#   Package configuration
+#------------------------------------------------------------------------------
+
+# Package configuration file
+PKG_CFLAGS=$(PKGCONFIGS:%=$(OBJROOT)/%.pkg-config.cflags)
+PKG_LDFLAGS=$(PKGCONFIGS:%=$(OBJROOT)/%.pkg-config.ldflags)
+$(OBJROOT)/pkg-config.mk: $(PKG_CFLAGS) $(PKG_LDFLAGS)
+	$(PRINT_COMMAND) (echo CFLAGS_PKGCONFIG=`cat $(PKG_CFLAGS)`; echo LDFLAGS_PKGCONFIG=`cat $(PKG_LDFLAGS)`) > $@
+-include $(PKGCONFIGS:%=$(OBJROOT)/pkg-config.mk)
+
+$(OBJROOT)/%.pkg-config.cflags: $(MAKEFILE_DEPS) $(OBJROOT)/.mkdir
+	$(PRINT_PKGCONFIG)  pkg-config --cflags $* > $@
+$(OBJROOT)/%.pkg-config.ldflags: $(MAKEFILE_DEPS) $(OBJROOT)/.mkdir
+	$(PRINT_COMMAND)  pkg-config --libs $* > $@
+
+
 #------------------------------------------------------------------------------
 #   Configuration rules
 #------------------------------------------------------------------------------
@@ -398,7 +406,7 @@ endif
 NORM_CONFIG=$(subst <,.lt.,$(subst >,.gt.,$(subst /,.sl.,$(CONFIG))))
 ORIG_TARGET=$(subst .lt.,<,$(subst .gt.,>,$(subst .sl.,/,$*)))
 CONFIG_DEPS=	$(MAKEFILE_DEPS) $(OBJDIR)/.mkdir			\
-		$(PKGCONFIGS:%=$(OBJROOT)/%.pkg-config.mk)
+		$(PKGCONFIGS:%=$(OBJROOT)/pkg-config.mk)
 
 config.h: $(NORM_CONFIG:%=$(OBJDIR)/CFG_HAVE_%.h)
 	$(PRINT_GENERATE) cat $^ > $@