How to require a semicolon after a macro

Question

So I am writing a library that has to build with -pedantic -ansi -std=c++98 -Werror and -Weverything for clang and -Wall -Wextra for gcc and I have this macro TESTSUITE(X) which is intended to be used in global scope like this:

TESTSUITE(current testsuite);

and what it does is call a function (on program startup by initializing a dummy var) with the string:

#define TESTSUITE(name) \
static int ANONYMOUS_VARIABLE(SOME_PREFIX) = setTestSuiteName(#name)

The problem is that this generates a warning under clang for -Wglobal-constructors.

If I surround it with _Pragma like this:

#define TESTSUITE(name)                                              \
_Pragma("clang diagnostic push");                                    \
_Pragma("clang diagnostic ignored \"-Wglobal-constructors\"");       \
static int ANONYMOUS_VARIABLE(SOME_PREFIX) = setTestSuiteName(#name) \
_Pragma("clang diagnostic pop")

the semicolon after using the macro will not be required for compilation (and when it is missing -pedantic gives an error).

If I add this at the end of the macro

static int ANONYMOUS_VARIABLE(SOME_PREFIX) = 5

the semicolon will be required but I will get a warning for an unused variable which I cannot silence (because if I surround it with _Pragma statements I will be back to square 1 not requiring a semicolon).

So does anyone have an idea how I can require the semicolon and also have 0 warnings?

Answer 1

A bit late to the party, but I thought I'd chime in for people looking for an answer later. The recommended way to achieve this is to just wrap the macro inside a do {....} while (0). This only gets executed once and the compiler will often optimize this away for you, generating no extra code but still achieving the abstraction.

Source: https://gcc.gnu.org/onlinedocs/cpp/Swallowing-the-Semicolon.html

Answer 2

Similar to @thomas-eding 's solution, you can put static_assert(true, "") at the end of a macro to require a semicolon.

This works both inside and outside classes and functions.

And it does not pollute any namespaces and does not generate any code.