I have a long list of constants that I need access to in several projects which are in different languages(Verilog, C, C++ and C#). Rather than repeating them in each language, is there a good way to share these?
The only thing I could think of would be a text file and a preprocessing script? Is this the best solution or is there something easier/more elegant?
You might have an XML file with the constants to be shared and have it parsed in each language.
A preprocessing script which automatically updates those constants within your code is probably the best method. Commit the code with your project to ensure correctness and have it a part of the build script.
You can keep them in a XML document and write XSLT scripts for each language to generate the appropriate source files in each build.
Can you use your makefile (or equivalent) to define these constants? For C and C++. you can use the compiler's CLI options to define pre-processor values for the constants. I haven't done much build customization for Verilog, but I suspect something similar might exist there as well.
You can write a simple file in the form of
const1 = value1
const2 = value2
const3 = value3
and then apply something like, for c:
s/\([a-zA-Z][a-zA-Z1-9_]*\)[ \t]*=[ \t]*\(.*\)/#define \1 \2/
Its worth noting that you might need to specify types because not all languages will allow you to use a preprossessor macro that doesn't care about type.
Alternatively, you can make a lexer/parser in Flex/Bison to parse the configuration file. This will be clearer and easier to extend.