Makefile generated when doing `gem install json` on Windows. For https://github.com/rubygems/rubygems/issues/977.

Makefile

SHELL = /bin/sh

# V=0 quiet, V=1 verbose.  other values don't work.
V = 0
Q1 = $(V:1=)
Q = $(Q1:0=@)
n=$(NULLCMD)
ECHO1 = $(V:1=@$n)
ECHO = $(ECHO1:0=@echo)

#### Start of system configuration section. ####

srcdir = .
topdir = /C/Ruby193/include/ruby-1.9.1
hdrdir = /C/Ruby193/include/ruby-1.9.1
arch_hdrdir = C:/Ruby193/include/ruby-1.9.1/$(arch)
VPATH = $(srcdir):$(arch_hdrdir)/ruby:$(hdrdir)/ruby

DESTDIR = C:
prefix = $(DESTDIR)/Ruby193
rubylibprefix = $(libdir)/$(RUBY_BASE_NAME)
exec_prefix = $(prefix)
vendorhdrdir = $(rubyhdrdir)/vendor_ruby
sitehdrdir = $(rubyhdrdir)/site_ruby
rubyhdrdir = $(includedir)/$(RUBY_BASE_NAME)-$(ruby_version)
vendordir = $(rubylibprefix)/vendor_ruby
sitedir = $(rubylibprefix)/site_ruby
ridir = $(datarootdir)/$(RI_BASE_NAME)
mandir = $(datarootdir)/man
localedir = $(datarootdir)/locale
libdir = $(exec_prefix)/lib
psdir = $(docdir)
pdfdir = $(docdir)
dvidir = $(docdir)
htmldir = $(docdir)
infodir = $(datarootdir)/info
docdir = $(datarootdir)/doc/$(PACKAGE)
oldincludedir = $(DESTDIR)/usr/include
includedir = $(prefix)/include
localstatedir = $(prefix)/var
sharedstatedir = $(prefix)/com
sysconfdir = $(prefix)/etc
datadir = $(datarootdir)
datarootdir = $(prefix)/share
libexecdir = $(exec_prefix)/libexec
sbindir = $(exec_prefix)/sbin
bindir = $(exec_prefix)/bin
rubylibdir = $(rubylibprefix)/$(ruby_version)
archdir = $(rubylibdir)/$(arch)
sitelibdir = $(DESTDIR)./.gem.20160114-12736-4wel7n
sitearchdir = $(DESTDIR)./.gem.20160114-12736-4wel7n
vendorlibdir = $(vendordir)/$(ruby_version)
vendorarchdir = $(vendorlibdir)/$(sitearch)

NULLCMD = :

CC = gcc
CXX = g++
LIBRUBY = lib$(RUBY_SO_NAME).dll.a
LIBRUBY_A = lib$(RUBY_SO_NAME)-static.a
LIBRUBYARG_SHARED = -l$(RUBY_SO_NAME)
LIBRUBYARG_STATIC = -l$(RUBY_SO_NAME)-static
empty =
OUTFLAG = -o $(empty)
COUTFLAG = -o $(empty)

RUBY_EXTCONF_H = 
cflags   =  $(optflags) $(debugflags) $(warnflags)
optflags = -O3 -fno-omit-frame-pointer
debugflags = -g
warnflags = -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration
CFLAGS   =  $(cflags) $(ARCH_FLAG)
INCFLAGS = -I. -I$(arch_hdrdir) -I$(hdrdir)/ruby/backward -I$(hdrdir) -I$(srcdir)
DEFS     = 
CPPFLAGS = -DJSON_GENERATOR -DFD_SETSIZE=2048 $(DEFS) $(cppflags)
CXXFLAGS = $(CFLAGS) $(cxxflags)
ldflags  = -L. 
dldflags =  -Wl,--enable-auto-image-base,--enable-auto-import $(DEFFILE) 
ARCH_FLAG = -march=i486
DLDFLAGS = $(ldflags) $(dldflags) $(ARCH_FLAG)
LDSHARED = $(CC) -shared $(if $(filter-out -g -g0,$(debugflags)),,-s)
LDSHAREDXX = $(CXX) -shared $(if $(filter-out -g -g0,$(debugflags)),,-s)
AR = ar
EXEEXT = .exe

RUBY_BASE_NAME = ruby
RUBY_INSTALL_NAME = ruby
RUBY_SO_NAME = msvcrt-ruby191
arch = i386-mingw32
sitearch = i386-msvcrt
ruby_version = 1.9.1
ruby = C:/Ruby193/bin/ruby
RUBY = $(ruby)
RM = rm -f
RM_RF = $(RUBY) -run -e rm -- -rf
RMDIRS = rmdir --ignore-fail-on-non-empty -p
MAKEDIRS = /usr/bin/mkdir -p
INSTALL = /usr/bin/install -c
INSTALL_PROG = $(INSTALL) -m 0755
INSTALL_DATA = $(INSTALL) -m 644
COPY = cp
TOUCH = exit >

#### End of system configuration section. ####

preload = 

libpath = . $(libdir)
LIBPATH =  -L. -L$(libdir)
DEFFILE = $(TARGET)-$(arch).def

CLEANFILES = mkmf.log $(DEFFILE)
DISTCLEANFILES = 
DISTCLEANDIRS = 

extout = 
extout_prefix = 
target_prefix = /json/ext
LOCAL_LIBS = 
LIBS = $(LIBRUBYARG_SHARED)  -lshell32 -lws2_32 -limagehlp -lshlwapi  
SRCS = generator.c
OBJS = generator.o
TARGET = generator
TARGET_NAME = generator
TARGET_ENTRY = Init_$(TARGET_NAME)
DLLIB = $(TARGET).so
EXTSTATIC = 
STATIC_LIB = 

BINDIR        = $(bindir)
RUBYCOMMONDIR = $(sitedir)$(target_prefix)
RUBYLIBDIR    = $(sitelibdir)$(target_prefix)
RUBYARCHDIR   = $(sitearchdir)$(target_prefix)
HDRDIR        = $(rubyhdrdir)/ruby$(target_prefix)
ARCHHDRDIR    = $(rubyhdrdir)/$(arch)/ruby$(target_prefix)

TARGET_SO     = $(DLLIB)
CLEANLIBS     = $(TARGET).so 
CLEANOBJS     = *.o  *.bak

all:    $(DLLIB)
static: $(STATIC_LIB)
.PHONY: all install static install-so install-rb
.PHONY: clean clean-so clean-rb

clean-static::
clean-rb-default::
clean-rb::
clean-so::
clean: clean-so clean-static clean-rb-default clean-rb
		-$(Q)$(RM) $(CLEANLIBS) $(CLEANOBJS) $(CLEANFILES) .*.time

distclean-rb-default::
distclean-rb::
distclean-so::
distclean: clean distclean-so distclean-rb-default distclean-rb
		@-$(RM) Makefile $(RUBY_EXTCONF_H) conftest.* mkmf.log
		@-$(RM) core ruby$(EXEEXT) *~ $(DISTCLEANFILES)
		@-$(RMDIRS) $(DISTCLEANDIRS) 2> /dev/null || true

realclean: distclean
install: install-so install-rb

install-so: $(RUBYARCHDIR)/$(DLLIB)	
$(RUBYARCHDIR)/$(DLLIB): $(DLLIB)
	-$(Q)$(MAKEDIRS) $(@D)
	$(INSTALL_PROG) $(DLLIB) $(@D)
clean-static::
	-$(Q)$(RM) $(STATIC_LIB)
install-rb: pre-install-rb install-rb-default
install-rb-default: pre-install-rb-default
pre-install-rb: Makefile
pre-install-rb-default: Makefile
pre-install-rb-default:
	$(ECHO) installing default generator libraries
./.RUBYARCHDIR.time:
	$(Q) $(MAKEDIRS) $(RUBYARCHDIR)
	$(Q) $(TOUCH) $@

site-install: site-install-so site-install-rb
site-install-so: install-so
site-install-rb: install-rb

.SUFFIXES: .c .m .cc .mm .cxx .cpp .o

.cc.o:
	$(ECHO) compiling $(<)
	$(Q) $(CXX) $(INCFLAGS) $(CPPFLAGS) $(CXXFLAGS) $(COUTFLAG)$@ -c $<

.mm.o:
	$(ECHO) compiling $(<)
	$(Q) $(CXX) $(INCFLAGS) $(CPPFLAGS) $(CXXFLAGS) $(COUTFLAG)$@ -c $<

.cxx.o:
	$(ECHO) compiling $(<)
	$(Q) $(CXX) $(INCFLAGS) $(CPPFLAGS) $(CXXFLAGS) $(COUTFLAG)$@ -c $<

.cpp.o:
	$(ECHO) compiling $(<)
	$(Q) $(CXX) $(INCFLAGS) $(CPPFLAGS) $(CXXFLAGS) $(COUTFLAG)$@ -c $<

.c.o:
	$(ECHO) compiling $(<)
	$(Q) $(CC) $(INCFLAGS) $(CPPFLAGS) $(CFLAGS) $(COUTFLAG)$@ -c $<

.m.o:
	$(ECHO) compiling $(<)
	$(Q) $(CC) $(INCFLAGS) $(CPPFLAGS) $(CFLAGS) $(COUTFLAG)$@ -c $<

$(DLLIB): $(DEFFILE) $(OBJS) Makefile
	$(ECHO) linking shared-object json/ext/$(DLLIB)
	-$(Q)$(RM) $(@)
	$(Q) $(LDSHARED) -o $@ $(OBJS) $(LIBPATH) $(DLDFLAGS) $(LOCAL_LIBS) $(LIBS)



$(DEFFILE): 
	$(ECHO) generating $(@)
	$(Q) $(RUBY) -e "puts 'EXPORTS', '$(TARGET_ENTRY)'"  > $@

###
generator.o: generator.c generator.h $(srcdir)/../fbuffer/fbuffer.h