bug#21683: 25.0.50; `advice-add` doesn't work for compiled primitive functions

[Philipp Stephani]

This is documented behavior:

https://www.gnu.org/software/emacs/manual/html_node/elisp/Advising-Named-Functions.html

It is possible to advise a primitive (see What Is a Function), but one should typically not do so, for two reasons. Firstly, some primitives are used by the advice mechanism, and advising them could cause an infinite recursion. Secondly, many primitives are called directly from C, and such calls ignore advice; hence, one ends up in a confusing situation where some calls (occurring from Lisp code) obey the advice and other calls (from C code) do not.

Vitalie Spinu <spinuvit@gmail.com> schrieb am Mi., 14. Okt. 2015 um 03:55 Uhr:

Hi,

Put this function into a file, compile the file and then load the file:


  (defun foobar ()
   (save-restriction
     (widen)))


then:


  (defun restrict-widen (orig-widen)
    (message "here")
    (apply orig-widen nil))

  (advice-add 'widen :around #restrict-widen)

  (foobar)



The advice is not triggered.


Eval the `foobar` definition interactively and the advice will start
working. The problem occurs only for primitive c functions. Elisp
functions are fine. It doesn't work with 24.4.1 either.


  Vitalie




In GNU Emacs 25.0.50.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.12.2)
 of 2015-09-26
Repository revision: 139e55a58466058a8c9ae54536cb790ac7b7cc64
Windowing system distributor 'The X.Org Foundation', version 11.0.11600000
System Description:     Ubuntu 14.10