Question

How can I create a typedef using a macro (#define)?

I am, for various reasons, trying to use a macro to do typedef’ing in C. Something along the lines of templates for C++.

As an example, I would expect the preprocessor to expand the #define and typedef a struct whose “content” member is of type char:

#define DEFINE_FOO_TYPE(content_type__, content_type_name__) \
typedef struct {                                             \
        content_type__ content;                              \
} content_type_name__

DEFINE_FOO_TYPE(char, foo_t);

foo_t foo_var;
foo_var.content = 'g';

Apparently that is not the case. Is it possible to do these sort of things in C at all, or is the only way a C++ template?

To preempt questions along the lines of “why don’t you just use a C++ template?”. The answer is that I’m trying to do it in C because it’s fun.

Answer 1

I posted in a comment because I thought it was too trivial, but here it is:

Surely you are not just pasting that quoted code into gcc, are you? You can’t just execute code outside any function. Put the last line inside a function.