[PATCH] Makefile: detect compiler and enable more warnings in DEVELOPER=1

From

Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

Date

Mar 18, 2018, 08:18 UTC

Message-ID

<20180318081834.16081-1-pclouds@gmail.com>

In-Reply-To

<20180317160832.GB15772@sigill.intra.peff.net>

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 -dumpversion does not work correctly for clang. So I use "-v" instead
 which seems to produce the same output for both gcc and clang (with a
 minor difference in freebsd where it says "FreeBSD clang" instead of
 just "clang"). Not sure if it helps your "cc on debian" case though

 Tested with clang-5.0.1 and gcc-6.4.0 (too lazy to test on freebsd
 clang 3.4.1 but I don't expect surprises there)

 I will still need to pull more modern gcc/clang on travis, but that
 can wait until this patch settles.

 Makefile        | 11 +----------
 config.mak.dev  | 28 +++++++++++++++++++++++++++
 detect-compiler | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 10 deletions(-)
 create mode 100644 config.mak.dev
 create mode 100755 detect-compiler

diff --git a/Makefile b/Makefile
index a1d8775adb..9dfd152a1e 100644
--- a/Makefile
+++ b/Makefile
@@ -442,15 +442,6 @@ GIT-VERSION-FILE: FORCE
 # CFLAGS and LDFLAGS are for the users to override from the command line.
 
 CFLAGS = -g -O2 -Wall
-DEVELOPER_CFLAGS = -Werror \
-	-Wdeclaration-after-statement \
-	-Wno-format-zero-length \
-	-Wold-style-definition \
-	-Woverflow \
-	-Wpointer-arith \
-	-Wstrict-prototypes \
-	-Wunused \
-	-Wvla
 LDFLAGS =
 ALL_CFLAGS = $(CPPFLAGS) $(CFLAGS)
 ALL_LDFLAGS = $(LDFLAGS)
@@ -1051,7 +1042,7 @@ include config.mak.uname
 -include config.mak
 
 ifdef DEVELOPER
-CFLAGS += $(DEVELOPER_CFLAGS)
+include config.mak.dev
 endif
 
 comma := ,
diff --git a/config.mak.dev b/config.mak.dev
new file mode 100644
index 0000000000..59aef342c4
--- /dev/null
+++ b/config.mak.dev
@@ -0,0 +1,28 @@
+CFLAGS += -Werror
+CFLAGS += -Wdeclaration-after-statement
+CFLAGS += -Wno-format-zero-length
+CFLAGS += -Wold-style-definition
+CFLAGS += -Woverflow
+CFLAGS += -Wpointer-arith
+CFLAGS += -Wstrict-prototypes
+CFLAGS += -Wunused
+CFLAGS += -Wvla
+
+COMPILER_FEATURES := $(shell ./detect-compiler $(CC))
+
+ifneq ($(filter clang4,$(COMPILER_FEATURES)),)
+CFLAGS += -Wtautological-constant-out-of-range-compare
+endif
+
+ifneq ($(or $(filter gcc6,$(COMPILER_FEATURES)),$(filter clang4,$(COMPILER_FEATURES))),)
+CFLAGS += -Wextra
+CFLAGS += -Wmissing-prototypes
+CFLAGS += -Wno-empty-body
+CFLAGS += -Wno-missing-field-initializers
+CFLAGS += -Wno-sign-compare
+CFLAGS += -Wno-unused-function
+CFLAGS += -Wno-unused-parameter
+ifneq ($(filter gcc6,$(COMPILER_FEATURES)),)
+CFLAGS += -Wno-maybe-uninitialized
+endif
+endif
diff --git a/detect-compiler b/detect-compiler
new file mode 100755
index 0000000000..bc2ea39ef5
--- /dev/null
+++ b/detect-compiler
@@ -0,0 +1,50 @@
+#!/bin/sh
+#
+# Probe the compiler for vintage, version, etc. This is used for setting
+# optional make knobs under the DEVELOPER knob.
+
+CC="$*"
+
+# we get something like (this is at least true for gcc and clang)
+#
+# FreeBSD clang version 3.4.1 (tags/RELEASE...)
+get_version_line() {
+	"$CC" -v 2>&1 | grep ' version '
+}
+
+get_family() {
+	get_version_line | sed 's/^\(.*\) version [0-9][^ ]* .*/\1/'
+}
+
+get_version() {
+	get_version_line | sed 's/^.* version \([0-9][^ ]*\) .*/\1/'
+}
+
+print_flags() {
+	family=$1
+	version=$(get_version | cut -f 1 -d .)
+
+	# Print a feature flag not only for the current version, but also
+	# for any prior versions we encompass. This avoids needing to do
+	# numeric comparisons in make, which are awkward.
+	while test "$version" -gt 0
+	do
+		echo $family$version
+		version=$((version - 1))
+	done
+}
+
+case "$(get_family)" in
+gcc)
+	print_flags gcc
+	;;
+*clang)
+	print_flags clang
+	;;
+"FreeBSD clang")
+	print_flags clang
+	;;
+*)
+	: unknown compiler family
+	;;
+esac

-- 
2.17.0.rc0.347.gf9cf61673a