25. Using GNU Autotools with Cygnus Cygwin

It is possible to use the GNU Autotools to build software packages on Windows. Since the tools were developed on Unix, it is easier to get them to work using Cygnus Solutions' Cygwin distribution which provides a POSIX wrapper for the Win32 API, See section The Diversity of Unix Systems, but it is certainly possible to run the tools within other Windows environments, notably Colin Peters' Mingw32 and D.J. Delorie's DJGPP. These development environments are freely available on the Internet(56). Unlike Cygwin, these other environments are designed for developing with the Win32 API directly and consequently they are not as useful for porting Unix projects to Windows or writing code that works on both Windows and Unix, see 15.3 Unix/Windows Portability for more details. This chapter describes the process of using GNU Autotools with Cygwin, although some of this advice also applies to employing some of the other GNU based Windows development environments.

It is notable that the recent Cygwin ports of GCC and binutils can produce binaries which will run with the `cygwin1.dll' emulation layer, or linked against `CRTDLL.DLL', the Windows native C RunTime Dynamic Link Library depending on the needs of particular source code. Recent versions(57) of the binutils implement the PE-COFF binary format used by Windows, so by specifying the `-mno-cygwin' compiler option to the Cygwin compiler and using only the API from `CRTDLL.DLL', you can build binaries which are independent of the `cygwin1.dll' DLL. Such binaries will generally run faster, since they bypass the POSIX emulation, and give easier access to Windows specific things such as drive letters. Source code designed to be compiled this way will not compile on Unix however, since it will be limited to the Win32 API provided by `CRTDLL.DLL'.

After reading this chapter, you will be able to install and use GNU Autotools natively under Windows using Cygnus Solutions' Cygwin environment, both to develop your own packages with the aid of Cygwin, and to compile, install, and to a certain degree port other peoples packages for use with Cygwin. As a Unix package developer, you will learn how to write your configury to be Windows friendly, and to be aware of certain quirks of Windows which can affect the portability of packages which need to work on Windows in addition to your Unix development machine.