Ruby-generated makefile doesn't run - ruby

Question

Maybe this is a really obvious answer, but I'm trying to extend Ruby using C in a Windows environment and I can't make the extension when I run mingw32-make it gets as far as generating a file called "forktest-i386-mingw32.def" and then says "No rule to make target 'ruby.h', needed by 'forktest.o'".
Forktest is the name of the extension that I'm trying to make.
The makefile was generated by ruby's own create_makefile command and it's really convoluted so I can't make heads or tales of it, but here it is anyway:
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 = $(ECHO1:0=#echo)
#### Start of system configuration section. ####
srcdir = .
topdir = /D/Programs/Ruby193/include/ruby-1.9.1
hdrdir = /D/Programs/Ruby193/include/ruby-1.9.1
arch_hdrdir = D:/Programs/Ruby193/include/ruby-1.9.1/$(arch)
VPATH = $(srcdir):$(arch_hdrdir)/ruby:$(hdrdir)/ruby
DESTDIR = D:
prefix = $(DESTDIR)/Programs/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 = $(sitedir)/$(ruby_version)
sitearchdir = $(sitelibdir)/$(sitearch)
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
OUTFLAG = -o
COUTFLAG = -o
RUBY_EXTCONF_H =
cflags = $(optflags) $(debugflags) $(warnflags)
optflags = -O3
debugflags = -g
warnflags = -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration
CFLAGS = $(cflags)
INCFLAGS = -I. -I$(arch_hdrdir) -I$(hdrdir)/ruby/backward -I$(hdrdir) -I$(srcdir)
DEFS =
CPPFLAGS = $(DEFS) $(cppflags)
CXXFLAGS = $(CFLAGS) $(cxxflags)
ldflags = -L.
dldflags = -Wl,--enable-auto-image-base,--enable-auto-import $(DEFFILE)
ARCH_FLAG =
DLDFLAGS = $(ldflags) $(dldflags)
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 = D:/Programs/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
#### 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 =
LOCAL_LIBS =
LIBS = $(LIBRUBYARG_SHARED) -lshell32 -lws2_32 -limagehlp
SRCS = forktest.c ruby.c
OBJS = forktest.o ruby.o
TARGET = forktest
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: $(STATIC_LIB)
.PHONY: all install static install-so install-rb
.PHONY: clean clean-so clean-rb
clean-rb-default::
clean-rb::
clean-so::
clean: clean-so clean-rb-default clean-rb
#-$(RM) $(CLEANLIBS) $(CLEANOBJS) $(CLEANFILES)
distclean-rb-default::
distclean-rb::
distclean-so::
distclean: clean distclean-so distclean-rb-default distclean-rb
#-$(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)
install-so: $(RUBYARCHDIR)/$(DLLIB)
$(RUBYARCHDIR)/$(DLLIB): $(DLLIB)
#-$(MAKEDIRS) $(#D)
$(INSTALL_PROG) $(DLLIB) $(#D)
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 forktest libraries
$(RUBYARCHDIR):
$(Q) $(MAKEDIRS) $#
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 $(DLLIB)
#-$(RM) $(#)
$(Q) $(LDSHARED) -o $# $(OBJS) $(LIBPATH) $(DLDFLAGS) $(LOCAL_LIBS) $(LIBS)
$(DEFFILE):
$(ECHO) generating $(#)
$(Q) $(RUBY) -e "puts 'EXPORTS', '' + 'Init_$(TARGET)'.sub(/\..*\z/,'')" > $#
$(OBJS): $(hdrdir)/ruby.h $(hdrdir)/ruby/defines.h $(arch_hdrdir)/ruby/config.h

Answer 1

I had the same issue and found that I accidentally had the MinGW Make on my path. This meant Ruby DevKit found that version before it's own msys version.
The mingw version doesn't handle the /D/Programs/Ruby193/ style of paths and produced the "No rule to make target 'ruby.h'..." error.
My solution was to remove MinGW make from my PATH so that Ruby DevKit found the msys version of Make when it runs (when it prints "Temporarily enhancing PATH to include DevKit...").
I checked my version of Make from the msys.bat environment (just run C:\devkit\msys.bat):
$ which make
# Should print a location like: C:\devkit\bin\make.exe
And check the version like this:
$ make --version
The correct msys version included this in the last line:
This program built for i686-pc-msys
The incorrect MinGW version output this:
GNU Make 4.1
Built for i686-w64-mingw32
I'm using ruby 2.2.3p173 and DevKit-mingw64-32-4.7.2-20130224-1151-sfx but this seems to be a PATH issue, not a ruby issue.