Stop continually re-creating build_version.c

Summary:
We continually rebuilt build_version.c because we put the
current date into it, but that's what __DATE__ already is.  This makes
builds faster.

This also fixes an issue with 'make clean FOO' not working properly.

Also tweak the build rules to be more consistent, always have warnings,
and add a 'make release' rule to handle flags for release builds.

Test Plan: make, make clean

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D8139

Makefile

@@ -9,9 +9,8 @@ INSTALL_PATH ?= $(CURDIR)
 # Uncomment exactly one of the lines labelled (A), (B), and (C) below
 # to switch between compilation modes.
 
-# OPT ?= -O2 -DNDEBUG       # (A) Production use (optimized mode)
-# OPT ?= -g2              # (B) Debug mode, w/ full line-level debugging symbols
-OPT ?= -O2 -g2 -DNDEBUG -Wall # (C) Profiling mode: opt, but w/debugging symbols
+# OPT ?= -DNDEBUG     # (A) Production use (optimized mode)
+OPT += -O3 -fno-omit-frame-pointer -momit-leaf-frame-pointer
 #-----------------------------------------------
 
 # detect what platform we're building on
@@ -19,8 +18,9 @@ $(shell ./build_detect_platform build_config.mk)
 # this file is generated by the previous line to set build flags and sources
 include build_config.mk
 
-CFLAGS += -Werror -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
-CXXFLAGS += -Werror -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT)
+WARNING_FLAGS = -Wall -Werror -Wno-unused-parameter -Wno-sign-compare
+CFLAGS += -g $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
+CXXFLAGS += -g $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT)
 
 LDFLAGS += $(PLATFORM_LDFLAGS)
 
@@ -65,7 +65,6 @@ TOOLS = \
 
 PROGRAMS = db_bench $(TESTS) $(TOOLS)
 BENCHMARKS = db_bench_sqlite3 db_bench_tree_db
-VERSIONFILE=util/build_version.cc
 
 LIBRARY = libleveldb.a
 MEMENVLIBRARY = libmemenv.a
@@ -99,13 +98,17 @@ $(SHARED3):
 
 endif  # PLATFORM_SHARED_EXT
 
-all: $(VERSIONFILE) $(SHARED) $(LIBRARY) $(TOOLS)
+all: $(SHARED) $(LIBRARY) $(PROGRAMS)
+
+release:
+	make clean
+	OPT=-DNDEBUG make -j32
 
 check: all $(PROGRAMS) $(TESTS) $(TOOLS)
 	for t in $(TESTS); do echo "***** Running $$t"; ./$$t || exit 1; done
 
 clean:
-	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) */*.o */*/*.o ios-x86/*/*.o ios-arm/*/*.o build_config.mk $(VERSIONFILE) */*.d
+	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) */*.o */*/*.o ios-x86/*/*.o ios-arm/*/*.o build_config.mk
 	-rm -rf ios-x86/* ios-arm/*
 
 $(LIBRARY): $(LIBOBJECTS)

build_detect_version

@@ -8,7 +8,8 @@
 #
 
 # create git version file
-VFILE=util/build_version.cc
+VFILE=$(mktemp)
+trap "rm $VFILE" EXIT
 
 # check to see if git is in the path
 which git > /dev/null
@@ -19,6 +20,10 @@ else
   echo "git not found"| awk ' BEGIN {print "#include \"build_version.h\""} {print "const char * leveldb_build_git_sha = \"leveldb_build_git_sha:git not found\";"} END {}' > ${VFILE}
 fi
 
-date | awk 'BEGIN {} {print "const char * leveldb_build_git_datetime = \"leveldb_build_git_datetime:"$0"\";"} END {} ' >> ${VFILE}
 echo "const char * leveldb_build_compile_date = __DATE__;" >> ${VFILE}
 echo "const char * leveldb_build_compile_time = __TIME__;" >> ${VFILE}
+
+OUTFILE=util/build_version.cc
+if [ ! -e $OUTFILE ] || ! cmp -s $VFILE $OUTFILE; then
+    cp $VFILE $OUTFILE
+fi

db/db_impl.cc

@@ -2385,8 +2385,8 @@ Status DestroyDB(const std::string& dbname, const Options& options) {
 // A global method that can dump out the build version
 void dumpLeveldbBuildVersion(Logger * log) {
   Log(log, "Git sha %s", leveldb_build_git_sha);
-  Log(log, "Git datetime %s", leveldb_build_git_datetime);
-  Log(log, "Compile time %s %s", leveldb_build_compile_time, leveldb_build_compile_date);
+  Log(log, "Compile time %s %s",
+      leveldb_build_compile_time, leveldb_build_compile_date);
 }
 
 }  // namespace leveldb

util/build_version.h

@@ -4,7 +4,6 @@
 
 // these variables tell us about the git config and time
 extern const char* leveldb_build_git_sha;
-extern const char* leveldb_build_git_datetime;
 
 // these variables tell us when the compilation occured
 extern const char* leveldb_build_compile_time;