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2.2 Building the library

As with any autoconfiguring GNU software, installation is as easy as this:

$ ./configure
$ make
$ make check

If on your system, ‘make’ is not GNU make, you have to use ‘gmake’ instead of ‘make’ above.

The configure command checks out some features of your system and C++ compiler and builds the Makefiles. The make command builds the library. This step may take about half an hour on an average workstation. The make check runs some test to check that no important subroutine has been miscompiled.

The configure command accepts options. To get a summary of them, try

$ ./configure --help

Some of the options are explained in detail in the ‘INSTALL.generic’ file.

You can specify the C compiler, the C++ compiler and their options through the following environment variables when running configure:


Specifies the C compiler.


Flags to be given to the C compiler when compiling programs (not when linking).


Specifies the C++ compiler.


Flags to be given to the C++ compiler when compiling programs (not when linking).


Flags to be given to the C/C++ preprocessor.


Flags to be given to the linker.


$ CC="gcc" CFLAGS="-O" CXX="g++" CXXFLAGS="-O" ./configure
$ CC="gcc -V 3.2.3" CFLAGS="-O2 -finline-limit=1000" \
  CXX="g++ -V 3.2.3" CXXFLAGS="-O2 -finline-limit=1000" \
  CPPFLAGS="-DNO_ASM" ./configure
$ CC="gcc-4.2" CFLAGS="-O2" CXX="g++-4.2" CXXFLAGS="-O2" ./configure

Note that for these environment variables to take effect, you have to set them (assuming a Bourne-compatible shell) on the same line as the configure command. If you made the settings in earlier shell commands, you have to export the environment variables before calling configure. In a csh shell, you have to use the ‘setenv’ command for setting each of the environment variables.

Currently CLN works only with the GNU g++ compiler, and only in optimizing mode. So you should specify at least -O in the CXXFLAGS, or no CXXFLAGS at all. If CXXFLAGS is not set, CLN will be compiled with -O.

The assembler language kernel can be turned off by specifying -DNO_ASM in the CPPFLAGS. If make check reports any problems, you may try to clean up (see Cleaning up) and configure and compile again, this time with -DNO_ASM.

If you use g++ 3.2.x or earlier, I recommend adding ‘-finline-limit=1000’ to the CXXFLAGS. This is essential for good code.

If you use g++ from gcc-3.0.4 or older on Sparc, add either ‘-O’, ‘-O1’ or ‘-O2 -fno-schedule-insns’ to the CXXFLAGS. With full ‘-O2’, g++ miscompiles the division routines. Also, do not use gcc-3.0 on Sparc for compiling CLN, it won’t work at all.

Also, please do not compile CLN with g++ using the -O3 optimization level. This leads to inferior code quality.

Some newer versions of g++ require quite an amount of memory. You might need some swap space if your machine doesn’t have 512 MB of RAM.

By default, both a shared and a static library are built. You can build CLN as a static (or shared) library only, by calling configure with the option ‘--disable-shared’ (or ‘--disable-static’). While shared libraries are usually more convenient to use, they may not work on all architectures. Try disabling them if you run into linker problems. Also, they are generally slightly slower than static libraries so runtime-critical applications should be linked statically.

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