Automatic build number generation

Version tracking is essential for several reasons. Without a proper versioning system it's difficult to know if this or that firmware contains certain update or feature, specially if one forgets to increment the version number.

That's where the build number appears, assigning a unique number per build (or 'make' in this special case). That way it can't go wrong. Version number is still there but there is also a build number, uniquely defining the release.

I usually never reset the build number, so even if the version number jumps (modified manually) the build number will always increment. It's not mandatory, it depends on how you feel about it.

Implementation

Here is an automatic build number generator. It's a shell script based on sh. I used it with Windows without any problems as long as sh and friends are available on the system path.

#!sh
# FILE: make_buildnum.sh
version="`sed  's/^ *//' major_version`"
old="`sed  's/^ *//' build.number` +1"
echo $old | bc > build.number.temp
mv build.number.temp build.number
#versión..
echo "$version`sed  's/^ *//' build.number` - `date`" > version.number
#header
echo "#ifndef BUILD_NUMBER_STR" > build_number.h
echo "#define BUILD_NUMBER_STR \"`sed  's/^ *//' build.number`\"" >> build_number.h
echo "#endif" >> build_number.h

echo "#ifndef VERSION_STR" >> build_number.h
echo "#define VERSION_STR \"$version`sed  's/^ *//' build.number` - `date`\"" >> build_number.h
echo "#endif" >> build_number.h

echo "#ifndef VERSION_STR_SHORT" >> build_number.h
echo "#define VERSION_STR_SHORT \"$version`sed  's/^ *//' build.number`\"" >> build_number.h
echo "#endif" >> build_number.h

In order to make it work a file named major_version has to be created. It should contain something like "1.02." (no double commas). A file called build.number is also needed. It will be the starting build number like "1". Version number won't be modified but build number will be incremented each time make_buildnum.sh is executed. In order to be useful for C programming the header file build_number.h is updated to reflect both build.number and major_version.

I usually create a makefile dependency to perform automatic build number generation by adding something like this to the Makefile:

# main rule
all: build_number.h $(TARGET).whatever $(TARGET).other
   @whatever rules

# rule for build number generation
build_number.h: $(SOURCES)
   @echo
   @echo Generating build number..
   sh make_buildnum.sh

A new build number is assigned every time a source file is modified. There can be other approachs too like generating a new build number even if no files were modified.

IMPORTANT: Under Windows care must be taken with CR and CRLF line endings. The files build.number and major_version have to be terminated with CRLF, otherwise sed and the other linux/unix utils won't be able to parse them.

Finally here is an example of what build_number.h looks like:

#ifndef BUILD_NUMBER_STR
#define BUILD_NUMBER_STR "1234"
#endif
#ifndef VERSION_STR
#define VERSION_STR "1.0.1234 - Fri Dec 19 11:00:23 HSE 2008"
#endif
#ifndef VERSION_STR_SHORT
#define VERSION_STR_SHORT "1.0.1234"
#endif

The bash script is easy to modify if any other information is needed, such as build number as a proper integer if some preprocessing is needed.