From bfb72ec2342409ff196bc5efa34ea367cb8c963e Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Thu, 4 Feb 2021 02:45:45 +0000
Subject: [PATCH] [build] Avoid spurious "make clean" when building for the
 first time

The function trace recorder build logic defaults to making "clean" a
dependency of the first build in a clean checkout.  This is redundant
and causes problems if the build process spins up multiple make
invocations to handle multiple build architectures.

Fix by replacing with logic based on the known-working patterns used
for the ASSERT and PROFILE build parameters.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/Makefile.housekeeping | 61 ++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 29 deletions(-)

diff --git a/src/Makefile.housekeeping b/src/Makefile.housekeeping
index 91be542ab..f379ff4ef 100644
--- a/src/Makefile.housekeeping
+++ b/src/Makefile.housekeeping
@@ -468,35 +468,6 @@ ASFLAGS		+= --fatal-warnings
 HOST_CFLAGS	+= -Werror
 endif
 
-# Function trace recorder state in the last build.  This is needed
-# in order to correctly rebuild whenever the function recorder is
-# enabled/disabled.
-#
-FNREC_STATE	:= $(BIN)/.fnrec.state
-ifeq ($(wildcard $(FNREC_STATE)),)
-FNREC_OLD	:= <invalid>
-else
-FNREC_OLD	:= $(shell cat $(FNREC_STATE))
-endif
-ifeq ($(FNREC_OLD),$(FNREC))
-$(FNREC_STATE) :
-else
-$(FNREC_STATE) : clean
-$(shell $(ECHO) "$(FNREC)" > $(FNREC_STATE))
-endif
-
-VERYCLEANUP	+= $(FNREC_STATE)
-MAKEDEPS	+= $(FNREC_STATE)
-
-ifeq ($(FNREC),1)
-# Enabling -finstrument-functions affects gcc's analysis and leads to spurious
-# warnings about use of uninitialised variables.
-#
-CFLAGS		+= -Wno-uninitialized
-CFLAGS		+= -finstrument-functions
-CFLAGS		+= -finstrument-functions-exclude-file-list=core/fnrec.c
-endif
-
 # Enable per-item sections and section garbage collection.  Note that
 # some older versions of gcc support -fdata-sections but treat it as
 # implying -fno-common, which would break our build.  Some other older
@@ -808,6 +779,38 @@ include/ipxe/profile.h : $(PROFILE_LIST)
 
 .PRECIOUS : include/ipxe/profile.h
 
+# (Single-element) list of function recorder configuration
+#
+FNREC_LIST := $(BIN)/.fnrec.list
+ifeq ($(wildcard $(FNREC_LIST)),)
+FNREC_OLD := <invalid>
+else
+FNREC_OLD := $(shell cat $(FNREC_LIST))
+endif
+ifneq ($(FNREC_OLD),$(FNREC))
+$(shell $(ECHO) "$(FNREC)" > $(FNREC_LIST))
+endif
+
+$(FNREC_LIST) : $(MAKEDEPS)
+
+VERYCLEANUP += $(FNREC_LIST)
+
+# Function recorder configuration
+#
+ifeq ($(FNREC),1)
+# Enabling -finstrument-functions affects gcc's analysis and leads to spurious
+# warnings about use of uninitialised variables.
+#
+CFLAGS		+= -Wno-uninitialized
+CFLAGS		+= -finstrument-functions
+CFLAGS		+= -finstrument-functions-exclude-file-list=core/fnrec.c
+endif
+
+include/compiler.h : $(FNREC_LIST)
+	$(Q)$(TOUCH) $@
+
+.PRECIOUS : include/compiler.h
+
 # These files use .incbin inline assembly to include a binary file.
 # Unfortunately ccache does not detect this dependency and caches
 # builds even when the binary file has changed.
-- 
2.47.3