I still don't have a fully working solution (see below). Hopefully someone can help figure out the reason for "Invalid read syntax: #" error.
OK, I found a workaround. Below solution works:
1. Eval the =org-macros= block once (=C-c C-c=)
- Always use that =org-macros= block to define the Org macros for this file.
- Hitting =C-c C-c= will insert those macros in this file.
- This block is reused as a noweb-ref in other blocks.. so keeping just this
block as a source for all Org macros will be convenient.
2. Then export that file (=C-c C-e h o=)
=====
#+BEGIN_SRC org :noweb-ref org-macros :results output replace :exports none
,#+MACRO: SEC_FOO Foo Topic
,#+MACRO: SEC_BAR Bar Topic
#+END_SRC
#+NAME: ehdr
#+BEGIN_SRC emacs-lisp :var macro="n" :noweb yes :results raw :exports none
(with-temp-buffer
(insert "
<<org-macros>>
\n")
(let ((start (point)))
(insert "// ---------------------------\n")
(insert (concat "// {{{" macro "}}}"))
(org-mode)
(org-macro-replace-all
(append org-macro-templates org-export-global-macros))
(buffer-substring-no-properties start (point-max))))
#+END_SRC
* Section 1: {{{SEC_FOO}}}
#+BEGIN_SRC verilog :noweb yes
<<ehdr(macro="SEC_FOO")>>
parameter A = 1;
#+END_SRC
* Section 2: {{{SEC_BAR}}}
#+BEGIN_SRC verilog :noweb yes
<<ehdr(macro="SEC_BAR")>>
parameter A = 1;
#+END_SRC
=====