Is it possible to pass a block of code as a macro argument?

Question

I'd like to wrap some lines of code with some boilerplate code, so should I do it by passing multiple lines of code as a macro argument like so:

#define safeRun(x) if (ValidationOK()) {x} 

int main(int argc, char **argv) {
    safeRun(
        foo();
        bar();
    )
}

Many thanks.

Answer 1

As written, your code will run foul of comma operators (but not, as previously claimed, commas in a function argument list).

Assuming you use C99, you can evade even that problem with variable arguments in the macro:

#define safeRun(...) if (ValidationOK()) {__VA_ARGS__}

int main(int argc, char **argv) {
    safeRun(
        foo(a, b),
        bar(c, d);
    )
}

Now, as far as the preprocessor is concerned, there are 2 arguments to the macro, separated by the commas, but they are handled as you want. Here's the gcc -E output:

# 1 "x3.c"
# 1 "<command-line>"
# 1 "x3.c"


int main(int argc, char **argv) {
    if (ValidationOK()) {foo(a, b), bar(c, d);}



}

Whether what you're proposing is a good idea is a separate discussion; these are the mechanisms that will more or less make it work.