Preprocessor macros are just substitution patterns applied to your code. They can be used almost anywhere in your code because they are replaced with their expansions before any compilation starts.
Inline functions are actual functions whose body is directly injected into their call site. They can only be used where a function call is appropriate.
Now, as far as using macros vs. inline functions in a function-like context, be advised that:
First, the preprocessor macros are just "copy paste" in the code before the compilation. So there is no type checking, and some side effects can appear
For example, if you want to compare 2 values:
#define max(a,b) ((a<b)?b:a)
The side effects appear if you use max(a++,b++)
for example (a
or b
will be incremented twice).
Instead, use (for example)
inline int max( int a, int b) { return ((a<b)?b:a); }