From 703412368c8afc811f2cec47684054e3875b607b Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sun, 31 Aug 2025 10:30:59 -0400
Subject: build: Allow ./configure CFLAGS=... to override auto-detected flags

---
 build/auto.mk | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 build/auto.mk

(limited to 'build/auto.mk')

diff --git a/build/auto.mk b/build/auto.mk
new file mode 100644
index 0000000..9cdf9e3
--- /dev/null
+++ b/build/auto.mk
@@ -0,0 +1,54 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile that generates gen/auto.mk
+
+include build/prelude.mk
+include gen/vars.mk
+include gen/early.mk
+include gen/late.mk
+include build/exports.mk
+
+# Auto-detected flags
+AUTO_FLAGS := \
+    gen/flags/std.mk \
+    gen/flags/bind-now.mk \
+    gen/flags/deps.mk \
+    gen/flags/pthread.mk \
+    gen/flags/Wformat.mk \
+    gen/flags/Wimplicit-fallthrough.mk \
+    gen/flags/Wimplicit.mk \
+    gen/flags/Wmissing-decls.mk \
+    gen/flags/Wmissing-var-decls.mk \
+    gen/flags/Wshadow.mk \
+    gen/flags/Wsign-compare.mk \
+    gen/flags/Wstrict-prototypes.mk \
+    gen/flags/Wundef-prefix.mk
+
+gen/auto.mk: ${AUTO_FLAGS}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@cat $^ >>$@
+	@cat ${^:%=%.log} >gen/flags.log
+	${VCAT} $@
+.PHONY: gen/auto.mk
+
+# Check that the C compiler works at all
+cc::
+	@build/cc.sh -q build/empty.c -o gen/.cc.out; \
+	    ret=$$?; \
+	    build/msg-if.sh "[ CC ] build/empty.c" test $$ret -eq 0; \
+	    exit $$ret
+
+# The short name of the config test
+SLUG = ${@:gen/%.mk=%}
+# The source file to build
+CSRC = build/${SLUG}.c
+# The hidden output file name
+OUT = ${SLUG:flags/%=gen/flags/.%.out}
+
+${AUTO_FLAGS}: cc
+	@${MKDIR} ${@D}
+	@build/flags-if.sh ${CSRC} -o ${OUT} >$@ 2>$@.log; \
+	    build/msg-if.sh "[ CC ] ${SLUG}.c" test $$? -eq 0
+.PHONY: ${AUTO_FLAGS}
-- 
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