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Preprocessing is a stage where preprocessor directives are expanded or processed before source code is sent to the compiler. The most common example of such directive is #include or #define. A preprocessor output has “. i” extension.
9) What is the output of C program with preprocessor directives.? Explanation: You can define a constant using Preprocessor directive even inside a main() function or any other function. So CVV is replaced by 199 everywhere it appears.
A typical use of the message pragma is to display informational messages at compile time. The message-string parameter can be a macro that expands to a string literal, and you can concatenate such macros with string literals in any combination.
The warning directive is probably the closest you'll get, but it's not entirely platform-independent:
#warning "C Preprocessor got here!"
AFAIK this works on most compilers except MSVC, on which you'll have to use a pragma directive:
#pragma message ( "C Preprocessor got here!" )
The following are supported by MSVC, and GCC.
#pragma message("stuff")
#pragma message "stuff"
Clang has begun adding support recently, see here for more.
You might want to try: #pragma message("Hello World!")
Most C compilers will recognize a #warning directive, so
#warning "Got here"
There's also the standard '#error' directive,
#error "Got here"
While all compilers support that, it'll also stop the compilation/preprocessing.
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