Preprocessor directives

Alexey_Ovchinnikov

Hi,
Recently I found OScript language reference page about preprocessor directives.
It says "Preprocessor directives are evaluated in the Livelink source code before being compiled" here https://knowledge.opentext.com/knowledge/cs.dll/fetch/-15106263/15106294/15106295/16376487/42329092/42440693/directives.html?nodeid=58572780&vernum=-2

Does they really work like preprocessor directives?
I tried to use them in CSIDE 10.5 and it seems like code between #ifdef #endif still gets compiled into oll. Does it work like usual if statement?

In standard CS modules #define is used inside functions and scripts.
Can we use #define globally? I mean like in C++ where we can have one .h file with tons of global #defines.

Mark_Sherry

The answer is "it's tricky".

If I write

#ifdef TEST_ONLY
public void runTests()
    // Run tests here...
end
#endif

then the feature will only be defined if I've d TEST_ONLY earlier in the file. Similarly, if I wrote

#define MAGIC_NUMBER 8675309
public Integer jennysNumber = MAGIC_NUMBER

we'll end up with a feature with a value of 8675309. Where it gets tricky is when it involves defines being tested and used inside of scripts and functions. While the preprocessor does its magic before the parse, and will type-check scripts and functions with those various substitutions made, the source for the scripts/functions is textually extracted from the source code and individually compiled into scripts.

The result is that these scripts are individually reparsed without the context of any surrounding #defines, so any #defines they rely on must be self contained. It differs from an if statement as it's only evaluated when compiled, rather than every execution.

In short: behaviour of #defines inside of scripts is mostly the same as before, although one needs to guard against defines leaking to other scripts during the parse of the OS file. Defines also work at the OS file level, which can be handy for including or excluding features conditionally, but defines outside of a script/function won't be seen inside of it when the script is being compiled.