Unix cc compiler to Microsoft's cl compiler wrapper
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cccl

Unix cc compiler to Microsoft's cl compiler wrapper at https://github.com/swig/cccl

Introduction

cccl is a wrapper around Microsoft's cl.exe Visual C++ compiler. It converts tradional Unix cc command line parameters to their cl.exe equivalents.

The main use for cccl is for using Unix build processes with the Microsoft C/C++ compiler. Using cccl in conjunction with ports of Unix utilities, it is possible to build many Unix packages using MSVC, without modifying the build process. This is especially useful if you want to use GNU autotools (autoconf/automake/libtool) with MSVC.

Motivation

Why would one use a wrapper script to make cl.exe act like gcc, when gcc is available for Windows?

There are a few reasons but the primary reason is usually to support cross-platform projects that need to use autoconf/automake/libtool for the build process. The obvious thing might be to use gcc on all platforms. But on Windows, not all third-party libraries work with gcc, some only work with MSVC.
cccl allows one to use the same build process with the MSVC compiler, but with only minimal changes to the build process.

Even though it's a somewhat simple approach, the original author, Geoffery Wossum, wrote the initial version of cccl and released it for others to use as it saved him a lot of hassle in the build process.

Usage Overview

cccl assumes cl.exe is in your path. cccl is run the same way that a Unix C or C++ compiler is used. Below shows usage to compile a simple C program:

$ cccl main.c -o runme.exe
main.c

By default cccl quietly passes the converted command line options to cl.exe. These can be displayed by using the --cccl-verbose option and can be useful for analysing compilation problems, for example:

$ cccl --cccl-verbose main.c -o runme.exe
cl "/nologo" "main.c" "/Ferunme.exe"
main.c

Getting Started

First, you'll want to install cccl. Then, you'll probably want to learn using autotools and MSVC together.

Installing cccl

Quick Overview

cccl is known to work on Cygwin and MinGW.

You can either copy the cccl script to somewhere on your system, or you can do a ./bootstrap && ./configure && make install from the source if you have a Unixish enough environment installed. The configure and Makefile don't really do anything but copy the cccl script, though.

Prerequisites

cccl uses and hence requires ports of the following Unix utilities:

  • bash
  • sed
  • tr

cccl is a bash shell script which makes use of these utilities. Therefore, you will need at the very least a Windows versions of these utilities. The easiest and best source of these (as well as many other Unix tools) is RedHat's Cygwin. Go to the Cygwin website to download and install Cygwin. If you are planning on using cccl to build autotools projects, make sure that you install autoconf, automake and libtool as well. Alternatively install MinGW instead of Cygwin.

Installing cccl

Once you have a working Cygwin or MinGW environment, you have two options. You may manually copy the cccl file to somewhere in your path, since it's just a script. Alternatively, you may do the normal Unix ./bootstrap && ./configure && make && make install routine.

Setting Up Your Path

Obviously you'll want cccl to be in your path. Since cccl directly invokes cl.exe, you'll need to make sure it is in your path as well. This may have been done for you during your Visual Studio install. If not, there should be a file called vcvars32.bat or vcvarsall.bat which can be run from an MS-DOS command prompt to set your path. Visual Studio usually installs a menu item to run a Visual Studio Command Prompt and is commonly under the Visual Studio Tools menu. This invokes one of the aforementioned batch files. Refer to the documentation included with Visual Studio for more details about running the Visual Studio command line tools. Note that the GNU linker is also called link.exe and is usually present in Cygwin and MinGW, but this shouldn't be a problem as cccl does not invoke the linker directly, it relies on cl.exe to invoke the appropriate Microsoft linker.

Autotools and MSVC

Autotools (autoconf, automake, libtool) and MSVC were never originally made to work together, but with cccl you can make them become reluctant friends.

configure.ac

Autoconf requires a file called configure.ac, which on legacy projects may still be called configure.in. In order to use autoconf and MSVC, make sure the following lines are in your configure.ac file:

AC_CANONICAL_SYSTEM
AC_CYGWIN
AC_OBJEXT
AC_EXEEXT

If your configure.ac file contains a reference to AM_PROG_LIBTOOL, add the following line before AM_PROG_LIBTOOL:

AC_LIBTOOL_WIN32_DLL

Makefile.am

Believe it or not, your Makefile.am files will probably not require any changes to work.

Convenience Libraries

Convenience libraries (noinst .a targets) work fine without any changes.

Executable Targets

No changes required. However, you may want to create a resource file to add the explorer icon to the .exe file.

Static Libraries

Autotools can build static libraries (.lib files) fine. However, you will probably want the output file to have a different name under Windows (super.lib vs. libsuper.a). You can accomplish this using some automake conditionals.

Dynamic Link Libraries (*.dll)

Older versions of the autotools (2.13 and earlier) didn't really support dynamic link libraries (.dll files) very well. Newer versions of Libtool have much improved Windows support for supporting dynamic link libraries.

Building Your Projects

Once you've generated your configure script and Makefiles by running aclocal, autoheader, autoconf and automake, you're ready to compile.

Before you run the configure script (from within Cygwin or MinGW, of course), you'll need to set the compiler and linker environment variables to use cccl.

export CC=cccl
export CXX=cccl
export LD=cccl

You may not need to set all these depending on whether your code base is just C or C++ and how the linker is invoked, but it is safest to set all three to begin with.

The options in Visual C++ are numerous and have changed over the years but have got a bit simpler more recently. Unlike gcc, the default options are not all that good though and often need tweaking. The good news is that the compiler will often tell you if you need to add an option, for example if you have C++ code that uses exceptions (any code that uses the STL uses exceptions), you should see a warning:

foo.cxx(10) : warning C4530: C++ exception handler used, but unwind semantics 
are not enabled. Specify /EHsc

Modern versions require /EHsc, but older versions require /GX. Depending on the version of cl.exe, you may need to add /GR to enable run-time type information (RTTI). Use:

export CXXFLAGS="/EHsc"

for new versions or for older versions:

export CXXFLAGS="/GX /GR"

The options starting with / such as /EHsc and /GX are unrecognized by cccl and are therefore passed directly to cl.exe.

Now, cross your fingers, and ./configure and make.

The Automake silent rules can control the verbosity of the output via the V variable. When make V=1 is used, cccl will display the options passed to cl.exe as if cccl --cccl-verbose was used.

Usage

cc on Unix serves as a front end to the compiler and the linker. Microsoft's cl.exe can operate the same but most usage is as a compiler.

Compiling

Any traditional cc options that cccl does not convert into options for cl.exe are passed unchanged to cl.exe. So options starting with - may or may not be converted. Any / options are expected to be for cl.exe and no attempt is made to convert them; they are passed directly to cl.exe unmodified. Further details about option conversions are in the Options section.

If cccl sees a C++ file with an extension other than .cpp (i.e. .cc, .C, or .cxx), then cccl will prepend a /Tp option to the cl.exe command line to force cl.exe to process it as a C++ source file.

Linking

cl.exe interprets all options after /link to be linker options. cccl may convert some options and if necessary pass them as a linker option by adding them after /link. There are a few approaches to passing additional options to the linker directly. The first is to specify them as you would with cl.exe where everything after /link is a linker option:

cccl main.c /W3 /link /LTCG /INCREMENTAL:NO

The second approach is to use the cccl option --cccl-link which passes just the single next option to the linker. If using this approach, the above example can be rewritten as follows:

cccl main.c --cccl-link /LTCG /W3 --cccl-link /INCREMENTAL:NO

Note that the first approach requires the compiler option /W3 to be placed before /link, whereas with the second approach the compiler option /W3 can be placed either before, after or as shown above right in between two linker options.

Both of the above examples will thus invoke cl.exe as follows:

cl main.c /W3 /link /LTCG /INCREMENTAL:NO

In the MinGW environment, / options are not supported very well and so are instead converted to - options and hence cccl will invoke cl.exe as follows:

cl main.c -W3 -link -LTCG -INCREMENTAL:NO

Verbosity

Visual C++ is unusually verbose for a compiler and displays the names of the files it is compiling and sometimes "Creating library" and similiar messages. For example, default output for compiling two or more files is shown below:

$ cccl main.c stuff.c -o runme.exe
main.c
stuff.c
Generating Code...

cccl supports the --cccl-muffle option which parses the output from cl.exe and suppresses this extra verbiage. Adding this option to the example results in silent output like traditional Unix compilers:

$ cccl main.c stuff.c -o runme.exe --cccl-muffle

The --cccl-verbose option will display exactly how cl.exe is invoked:

$ cccl main.c stuff.c -o runme.exe --cccl-verbose
cl "/nologo" "main.c" "stuff.c" "/Ferunme.exe"
main.c
stuff.c
Generating Code...

Environment

cccl supports the CCCL_OPTIONS environment variable. The contents of the environment variable are treated as additional command line options to cccl. This can be handy for adding additional options or tweaking the verbosity options without changing the build system. For example:

$ export CCCL_OPTIONS="--cccl-muffle --cccl-verbose /W3"
$ cccl -O2 main.c
cl "/nologo" "/W3" "/O2" "main.c"

and assuming CCCL_OPTIONS is not set, then the above is the same as:

$ cccl --cccl-muffle --cccl-verbose /W3 -O2 main.c
cl "/nologo" "/W3" "/O2" "main.c"

There is one notable difference using CCCL_OPTIONS compare to using actual options and that is the handling of spaces within options, for example -I"My Headers". For this to work, you must pass it as a real cccl command line option and CCCL_OPTIONS can't be used.

Options

The following Unix compiler cc/gcc options are understood by cccl:

  • -ansi Converts to cl.exe's /Za
  • -c Converts to cl.exe's /C
  • -g[0-9] Converts to cl.exe's /Zi
  • -O0 Converts to cl.exe's /Ot optimization option
  • -L_path_ Converts to linker option /LIBPATH:path
  • -l_library_ Converts to lib_library_.lib
  • -m386 Converts to cl.exe's /G3
  • -m486 Converts to cl.exe's /G4
  • -mpentium Converts to cl.exe's /G5
  • -mpentiumpro Converts to cl.exe's /G6
  • -o is converted to /Fo for object files and /Fe for executables and dlls
  • -pedantic Removed/ignored, cl.exe does not support any equivalent
  • -W Removed/ignored
  • -fno-strict-aliasing Removed/ignored
  • -isystem Converted to /I
  • -MT Due to conflict with cl.exe's /MT option, there is no support and cccl exits
  • -mno-cygwin Removed/ignored
  • -shared Converts to cl.exe's /LD or /LDd if -g is used
  • *.(cc|cxx|C) C++ source file is passed using /Tp

The following are cccl specific options:

  • --help Displays cccl help
  • --cccl-link Passes the following option as a linker option
  • --cccl-muffle Removes cl.exe's verbiage (file names being compiled etc) from being displayed
  • --cccl-verbose Displays how cl.exe is invoked
  • --cccl-version Displays cccl's version string

All other - options are passed untouched to cl.exe. All / options are passed unmodified to cl.exe. All other non-options (file/path names) are also passed on unmodified.

History

Version 0.01

Geoffrey Wossum (gwossum@acm.org) first wrote cccl as a Bourne shell script and released it under the GPL license at http://cccl.sf.net on 9 August 2001. The original cccl SourceForge project page is located at http://sf.net/projects/cccl.

Version 0.03

This version contained a few patches and was released in January 2003 and was the last version released on Sourceforge.

2003 to 2015

The original was forked a few times. The known public forks are:

Version 1.0

William Fulton had been using cccl with some unpublished modifications for testing and building SWIG releases for many years. In 2015, these were made public and merged with the Open vSwitch fork and released on Github at https://github.com/swig/cccl under the newer GPL version 3 license.

The documentation was also converted to Markdown format and brought up to date.

New Features

The main improvements in version 1.0 over the original cccl release 0.03 are:

  • Support for compiling and linking in a single step works with a mix of C, C++ and object files as inputs.
  • Support for spaces in paths, such as include paths and spaces in file names.
  • Support for creating dynamic link libraries (dlls).
  • Support for running under MinGW.
  • Adding control of output verbosity.
  • Simpler setup configuration by avoiding using link.exe directly, which previously may have incorrectly invoked the GNU linker.

Future

The move to Github at https://github.com/swig/cccl is hoped to inject some life into the project on a modern open source platform as the Sourceforge project had been defunct for 12 years.

The goal is for cccl to remain simple and lightweight so that the performance degradation added by the wrapper is kept small. Pull requests from users for bug fixes and improvements that meet these goals are encouraged.

See Also

wgcc is another cccl like tool for Interix but was superceded by parity.