Answer by HolyBlackCat for Detect a parenthesized macro argument in C

#define FOO(...) DETAIL_FOO1( DETAIL_FOO0 __VA_ARGS__ ) )#define DETAIL_FOO0(...) DETAIL_FOO0_ __VA_ARGS__#define DETAIL_FOO1(...) DETAIL_FOO2(__VA_ARGS__)#define DETAIL_FOO2(...) DETAIL_FOO3_##__VA_ARGS__#define DETAIL_FOO3_DETAIL_FOO0 (#define DETAIL_FOO3_DETAIL_FOO0_ bar(FOO(1) // (1)FOO((1,2,3)) // bar(1,2,3)

In this case FOO(1) expands to (1) and not 1, but this is probably more desirable.

Turns out this incorrectly accepts FOO((1,2)3), expanding it to bar(1,2 3). With additional macro gymnastics you can reject that:

#define FOO(...) DETAIL_FOO1( DETAIL_FOOA(__VA_ARGS__) ) )#define DETAIL_FOOA(...) DETAIL_FOO0 __VA_ARGS__ )#define DETAIL_FOO0(...) DETAIL_FOO0_ __VA_ARGS__ REQUIRE_EMPTY(#define DETAIL_FOO1(...) DETAIL_FOO2(__VA_ARGS__)#define DETAIL_FOO2(...) DETAIL_FOO3_##__VA_ARGS__#define DETAIL_FOO3_DETAIL_FOO0 ( IDENTITY(#define DETAIL_FOO3_DETAIL_FOO0_ bar(#define REQUIRE_EMPTY()#define IDENTITY(...) __VA_ARGS__