Want to compile only if statement in if-else-CodePudding

I am working on a project which should have to run on both ros melodic (ubuntu 18.04) and ros noetic(ubuntu 20.04). so while doing so I made an if-else statement in my code that,

if(distro=="noetic"){
    ...do this
else
    ...do this

The problem occurs basically, noetic and melodic support different versions of Point cloud Libraries(PCL) which also make them different in their way of initialization. So when I put PCL initialization (the way noetic support) in the if statement and in the else statement I put melodic way of initialization. I want the compiler( catkin_make command I use) to compile only the if statement but it also compiles else statement which gives an error because noetic did not support a melodic way of initialization. What should be the way?

CodePudding user response：

Use preprocessor macros. This needs to be handled before compile time. The preprocessor macros #ifdef and #ifndef will check if a token is present in the symbol table (check the documentation for your OS to see if there is a defined token for it), and skip to the according if/else section.


#ifdef NOETIC_DISTRO
//Code for noetic distro
#endif
#ifdef OTHER_DISTRO
//Code for other distro
#endif