Thursday, August 11, 2005

Teaching configure about build flags

Cobbled together from several sources around the Internet, I put together a solution this morning to a question posed by one of our developers: how do you make debug v release builds with GNU autotools?

A first pass at answering produced the ac_build_types.m4 macro for autoconf. First, some usage. Here is configure.ac:

AC_PREREQ(2.59)
AC_INIT([my_project], [0.0.0], [binkley@alumni.rice.edu])
AC_CONFIG_SRCDIR([config.h.in])
AC_CONFIG_HEADER([config.h])
AM_INIT_AUTOMAKE

AC_BUILD_TYPES

dnl Rest of file...

The only thing different from a standard configure.ac is the addition of AC_BUILD_TYPES. The effect of that shows in ./configure:

$ ./configure --help
# ...
Optional Features:
  --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
  --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
  --enable-debug          build debug version
  --enable-profile        build profiling version
  --enable-release        build release version
# ...

Now there are flags to build debug, profiling and release builds.

Last is the macro itself:

C_DEFUN([AC_BUILD_TYPES],
[
AC_ARG_ENABLE(debug,
      [  --enable-debug          build debug version],
      CFLAGS="$CFLAGS -DDEBUG -O0 -g3 -Wall"
      CXXFLAGS="$CXXFLAGS -DDEBUG -O0 -g3 -Wall")
AC_ARG_ENABLE(gprof,
      [  --enable-profile        build profiling version],
      CFLAGS="$CFLAGS -pg"
      CXXFLAGS="$CXXFLAGS -pg"
      LDFLAGS="$LDFLAGS -pg")
AC_ARG_ENABLE(release,
      [  --enable-release        build release version],
      CFLAGS="$CFLAGS -DNDEBUG -g0 -O3"
      CXXFLAGS="$CXXFLAGS -DNDEBUG -g0 -O3")
])

That's all! Save the definition into something like ac_build_types.m4 and run aclocal -Idirectory-containing-macros as part of creating your ./configure for other developers.

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