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

The set of extra warnings we enable when DEVELOPER has to be
conservative because we can't assume any compiler version the
developer may use. Detect the compiler version so we know when it's
safe to enable -Wextra and maybe more.

These warning settings are mostly from my custom config.mak a long
time ago when I tried to enable as many warnings as possible that can
still build without showing warnings. Some of those warnings are
probably worth fixing instead of just suppressing in future.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
tags/v2.18.0-rc0
Nguyễn Thái Ngọc Duy Junio C Hamano 1 year ago
parent
commit
1da1580e4c
3 changed files with 96 additions and 10 deletions
  1. +5
    -10
      Makefile
  2. +38
    -0
      config.mak.dev
  3. +53
    -0
      detect-compiler

+ 5
- 10
Makefile View File

@@ -431,6 +431,10 @@ all::
#
# When cross-compiling, define HOST_CPU as the canonical name of the CPU on
# which the built Git will run (for instance "x86_64").
#
# Define DEVELOPER to enable more compiler warnings. Compiler version
# and family are auto detected, but could be overridden by defining
# COMPILER_FEATURES (see config.mak.dev)

GIT-VERSION-FILE: FORCE
@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -439,15 +443,6 @@ 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)
@@ -1047,7 +1042,7 @@ include config.mak.uname
-include config.mak

ifdef DEVELOPER
CFLAGS += $(DEVELOPER_CFLAGS)
include config.mak.dev
endif

comma := ,

+ 38
- 0
config.mak.dev View File

@@ -0,0 +1,38 @@
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

ifndef COMPILER_FEATURES
COMPILER_FEATURES := $(shell ./detect-compiler $(CC))
endif

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
# if a function is public, there should be a prototype and the right
# header file should be included. If not, it should be static.
CFLAGS += -Wmissing-prototypes
# These are disabled because we have these all over the place.
CFLAGS += -Wno-empty-body
CFLAGS += -Wno-missing-field-initializers
CFLAGS += -Wno-sign-compare
CFLAGS += -Wno-unused-function
CFLAGS += -Wno-unused-parameter
endif

# uninitialized warnings on gcc 4.9.2 in xdiff/xdiffi.c and config.c
# not worth fixing since newer compilers correctly stop complaining
ifneq ($(filter gcc4,$(COMPILER_FEATURES)),)
ifeq ($(filter gcc5,$(COMPILER_FEATURES)),)
CFLAGS += -Wno-uninitialized
endif
endif

+ 53
- 0
detect-compiler View File

@@ -0,0 +1,53 @@
#!/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
;;
"Apple LLVM")
print_flags clang
;;
*)
: unknown compiler family
;;
esac

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