Thanks so much.  It sort of works but with a bit of work-around:

1) tangle works fine

2) for export, I had to move the 
> ,#+MACRO: SEC_FOO 
lines out of the code block.  If I didn’t and tried to eval that block, I got the error

   No org-babel-execute function for org!

But I think this will do what I need. Of course emacs / org couldn’t have a simple preproccessor-like macro :)

  David 

Sent from my iPhone

> On Nov 1, 2017, at 9:17 AM, Kaushal Modi <kaushal.modi@gmail.com> wrote:
> 
>> On Wed, Nov 1, 2017 at 11:51 AM Kaushal Modi <kaushal.modi@gmail.com> wrote:
>> 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 
> =====
> -- 
> Kaushal Modi