Variadic macro with no arguments for its variadic parameter

心不动则不痛 提交于 2019-12-05 05:26:21

Otherwise, there shall be more arguments in the invocation than there are parameters in the macro definition (excluding the ...).

This very extract from the standard shows that your code should not be valid: you have one parameter plus the ellipsis. If we follow the portion of the standard above, you should have at least two arguments. When you write varidadic(1), you just provide one argument. Your code is not valid.

By the way, clang produces a warning:

main.cpp:7:32: warning: must specify at least one argument for '...' parameter of variadic macro [-Wgnu]
    std::cout << "'" variadic(1) "'" << std::endl;

And GCC also produces a warning:

main.cpp:7:32: warning: ISO C99 requires rest arguments to be used [enabled by default]
     std::cout << "'" variadic(1) "'" << std::endl;

Since that may be a bother to the programmer, and since the programmer's intent is easy to guess, they both consider variadic(1) is equivalent to variadic(1,).

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