add BINDIR in Makefile

[ewwissi]

the obj and bin files are stored under source code directory,
would like to add a BINDIR in Makefile,
to support parralle make for different target.

[bnoordhuis]

BINDIR is normally used to install executables to. http-parser however doesn't produce executables, only libraries. (I'm ignoring the test runner; it isn't installed.)

Perhaps what you're really asking for is VPATH support for out-of-tree builds?

[ewwissi]

maybe BINDIR is not a good name, it is the direcotry where obj and exe files are stored during make,
it can solve problem when running parralle make with different arch,

change looks like:

BINDIR ?= $(CURDIR)

test: $(BINDIR)/test_g $(BINDIR)/test_fast
$(HELPER) $(BINDIR)/test_g$(BINEXT)
$(HELPER) $(BINDIR)/test_fast$(BINEXT)

$(BINDIR)/test_g: $(BINDIR)/http_parser_g.o $(BINDIR)/test_g.o
$(CC) $(CFLAGS_DEBUG) $(LDFLAGS) -o $@ $^

$(BINDIR)/test_g.o: test.c http_parser.h Makefile
$(CC) $(CPPFLAGS_DEBUG) $(CFLAGS_DEBUG) -c test.c -o $@

$(BINDIR)/http_parser_g.o: http_parser.c http_parser.h Makefile
$(CC) $(CPPFLAGS_DEBUG) $(CFLAGS_DEBUG) -c http_parser.c -o $@

[bnoordhuis]

Right, that's traditionally solved with VPATH, although your approach works too for simple projects.

What you call BINDIR is usually called BUILDDIR or sometimes just B. Pull requests welcome but note that I plan on switching to cmake sometime this year and cmake gives you out-of-tree builds for free.