[cfe-dev] How to find macro arguments?

[Mario Schwalbe]

Hi all,

I'm trying to familiarize myself with clang and in particular its AST matchers.
Therefore, I tried to write some piece of code to determine if an expression
has been passed as an argument to a macro:

    auto& context = /* ASTContext */
    auto& SM = context.getSourceManager();
    auto loc = expr.getLocStart();

    if (SM.isMacroArgExpansion(loc)) {
        const auto expLoc = SM.getImmediateExpansionRange(loc).first;
        const auto name   = Lexer::getImmediateMacroName(expLoc, SM, context.getLangOpts());
        if (name == "MACRO")
            return true;
    }

Given the following code:

#define MACRO(v)  (v + 1) - 2

int test(int x)
{
    return MACRO(x);
}

it also returns true for the expression `x + 1' (BinaryOperator) within
the macro expansion, not just the DeclRefExpr `x' itself. Looks like both
expressions have the same location (I dumped its internal representation).
But why? And how can the 2 cases be distinguished? Or what am I missing here?
Thanks in advance for any pointers.

ciao,
Mario