Getting the signature of a FunctionDecl

Question

I got the FunctionDecl for the definition of a function. There is no declaration for this function.

For example:

int foo(char c, double d)
{
   ...
}

How do I get the signature (qualifier, return type, function name, parametrs) as a valid signature I could use to make a declaration?

Answer 1

I found that the easiest way is to use the lexer to get the signature of the function. Since I wanted to make a declaration out of a definition, I wanted the declaration to look exactly like the definition. Therefore I defined a SourceRange from the start of the function to the beginning of the body of the function (minus the opening "{") and let the lexer give me this range as a string.

static std::string getDeclaration(const clang::FunctionDecl* D)
{
  clang::ASTContext& ctx = D->getASTContext();
  clang::SourceManager& mgr = ctx.getSourceManager();

  clang::SourceRange range = clang::SourceRange(D->getSourceRange().getBegin(), D->getBody()->getSourceRange().getBegin());
  StringRef s = clang::Lexer::getSourceText(clang::CharSourceRange::getTokenRange(range), mgr, ctx.getLangOpts());

  return s.substr(0, s.size() - 2).str().append(";");
}

This solution assums that the FunctionDecl is a definition (has a body).