CppCMS For embedded systems
General
Generally CppCMS can be used as-is for embedded systems. However there are many features that are heavy and targeted for high performance web servers. These options are rather useless for embedded system.
Thus additional build options that make this library optimized for embedded system provided.
They are reduce number of dependencies and make executable significantly smaller.
Changes in Embedded Build
Normal Embedded Build
- Caching is completely removed. Small memory footprint is very important for embedded system thus, caching stuff in memory is quite useless.
- Zlib compression are removed – it removes dependency on
boost::iostreams, zlib and bzip2 libraries. - Removed mod-prefork.
- Removed dynamic templates loading — this feature requires export of symbols to binary and increases its size in order to make RTTI work. Thus, all templates should be statically compiled into the binary.
CGI Mode
- FastCGI and SCGI APIs are removed
- Mod-thread and mod process are removed including all thread pool facilities
- Changes in files based session backend to work properly with CGI mode including garbage collection (sessions that had time-out).
Minimal Dependencies
Embedded compilation allows building CppCMS using only following libraries:
- libcgicc
- libboost_signals
- libboost_regex.
Cross Compilation of CppCMS
General
For cross compilation you should use --host configuration switch according to your platform, for example:
./configure --host=arm-linux-eabi ... ./configure --host=mips-linux-gnu
Do not forget to build boost and cgicc as well. Refer to your platform documentation for cross-compilation instructions.
Build Flags:
--enable-embedded– Create embedded version of cppcms.--enable-cgi– implement CGI API only.
Additional flags:
CXXFLAGS=-Os– optimize for size when you build for embedded system--prefix=/...– always specify installation prefix… You do not want to install to/usr/local/lib,;-)
For example:
./configure --host=arm-linux-gnu --prefix=/usr/arm-linux-gnu CXXFLAGS=-Os --enable-embedded --enable-cgi
Would configure cross compilation make files for ARM platform,
Notes:
- Remember that you should build cgicc and boost as well
- It is recommended to build
boost::regexwithout ICU support in order to reduce executable size. - Use
strip --strip-allto reduce your executable size.
Static Linking
In some cases you want to build your application without dependencies on many shared objects. Thus you can link your application "almost" statically.
Only system libraries like libc, libstdc++, pthreads, rt would be linked dynamically
CGI Only
You can build "almost" static build as following:
g++ hello.o /path/to/libcppcms.a /path/to/libcppcmstranstext.a /path/to/libboost_signals.a /path/to/libboost_regex.a /path/to/libcgicc.a
With Worker Threads
You can build "almost" static build as following:
g++ hello.o /path/to/libcppcms.a /path/to/libcppcmstranstext.a /path/to/libboost_signals.a /path/to/libboost_regex.a /path/to/libcgicc.a -lrt -lpthread