syntax error: failed to expand 'HASH_TOKEN_IN_MACRO'

[chrchr-github]

From https://trac.cppcheck.net/ticket/12105

void g(const char*);
#define HASH_TOKEN_IN_MACRO( A ) g( #A )
void f() {
    HASH_TOKEN_IN_MACRO (
#ifdef SW
        "Message 1"
#else
        "Message 2"
#endif
    );
}

foo.cpp:5: syntax error: failed to expand 'HASH_TOKEN_IN_MACRO', it is invalid to use a preprocessor directive as macro parameter

[danmar]

This code is undefined behavior.

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

page 152

If there are sequences of preprocessing tokens within the list of arguments that would otherwise act as preprocessing directives,150) the behavior is undefined

[parrotrueper]

@danmar Agreed that the code is bad, the linter should flag it and carry on, rather than grind to a halt and stop checking the rest of the code. As a side note this code was created to evaluate linters. Out of five linters Cppcheck was the only one that stopped checking after encountering this error.

[danmar]

@parrotrueper I would hope you can consider to fix the evaluation code somehow then. And evaluate cppcheck using that. A user would fix the code and then recheck..

[danmar]

alright I guess we can reopen this. Fixing this doesn't mean we have to remove the error message...