Building rsyslog from the source repository
In most cases, people install rsyslog either via a package or use an "official" distribution tarball to generate it. But there may be situations where it is desirable to build directly from the source repository. This is useful for people who would like to participate in development or who would like to use the latest, not-yet-released code. The later may especially be the case if you are asked to try out an experimental version.
Building from the repository is not much different than building from the source tarball, but some files are missing because they are output files and thus do not belong into the repository.
Obtaining the Source
First of all, you need to download the sources. Rsyslog is kept in git. The "Where to find the rsyslog source code" page on the project site will point you to the current repository location.
After you have cloned the repository, you are in the master branch by default. This is where we keep the devel branch. If you need any other branch, you need to do a "git checkout --track -b branch origin/branch". For example, the command to check out the beta branch is "git checkout --track -b beta origin/beta".
To build the compilation system, you need the pkg-config package (an utility for autotools) present on your system. Otherwise, configure will fail with something like
checking for SYSLOG_UNIXAF support... yes checking for FSSTND support... yes ./configure: line 25895: syntax error near unexpected token `RELP,' ./configure: line 25895: ` PKG_CHECK_MODULES(RELP, relp >= 0.1.1)'
Creating the Build Environment
This is fairly easy: just issue "autoreconf -fvi", which should do everything you need. Once this is done, you can follow the usual ./configure steps just like when you downloaded an official distribution tarball (see the rsyslog install guide, starting at step 2, for further details about that).
Special Compile-Time Options
On some platforms, compile-time issues occur, like the one shown below:
make: Entering directory `/home/az/RSyslog/rsyslog-5.5.0/tools' CCLD rsyslogd rsyslogd-omfile.o: In function `getClockFileAccess': /home/az/RSyslog/rsyslog-5.5.0/tools/omfile.c:91: undefined reference to `__sync_fetch_and_add_8' /home/az/RSyslog/rsyslog-5.5.0/tools/omfile.c:91: undefined reference to `__sync_fetch_and_add_8' /home/az/RSyslog/rsyslog-5.5.0/tools/omfile.c:91: undefined reference to `__sync_fetch_and_add_8'
Note that the exact error messages can be different. These type of errors stem down to atomic instruction support in GCC, which is somewhat depending on the machine architecture it compiles code for. Very old machines (like the original i386) do not even at all provide support for these instructions.
The availability of atomic instructions is vital for rsyslog - it can not be built without them. Consequently, there is a configure check included for them. But under some circumstances, GCC seems to report they are available, but does not provide implementations for all of them (at least this is my observation...). The simple cure is to make sure that GCC generates code for a modern-enough architecture. This, for example, can be done as follows:
./configure CFLAGS="-march=i586 -mcpu=i686" --enable-imfile ... (whatever you need)
These settings should resolve the issue.