[Emacs-ada-mode] [Emacs][ada-mode] ada-xref.el -- missing gnatls in PATH

[Pierre-Louis Escouflaire]

Hello,

We found a relatively drastic problem related to the 'ada-xref.el' 
script file that appears when you do NOT have 'gnatls' in your PATH.

Here are a few commands to reproduce the problem:
(Please make a backup of your .emacs)

$
$ alias emacs=$(which emacs)
$ cp .emacs /tmp/.emacs
$ cat << EOF > .emacs
(require 'ada-xref)
;; The following lines won't be executed
(set-background-color "black")
(set-foreground-color "white")
EOF
$ export oPATH=${PATH}
$ export PATH=:
$ emacs
--> emacs appears but shows some errors
--> The lines for background and foreground are not executed
$ export PATH=${oPATH}
$ mv /tmp/.emacs .emacs
$


The reason is located around line 300 in 'ada-xref.el':
...
  (let* ((gnatls (ada-find-executable (concat cross-prefix "gnatls")))
	(status (call-process gnatls nil t nil "-v")))
...


In fact, the `ada-find-executable' function returns:
   . the full path to the executable when found ;
   . the string given as an argument when not found.

Thus,   (ada-find-executable "gnatls")   returns "gnatls" when there is 
NO 'gnatls' in your PATH.

Thus, I think that your code misses a check that the "found" 'gnatls' 
exists and is executable (file-executable-p) between the call to 
`ada-find-executable' and the call to `call-process'.

Another solution (maybe wiser) would be to change `ada-find-executable' 
so that it raises an error when the executable has not been found. The 
one using it should then protect it using a `condition-case'.



Thanks for your concern.

Regards,
Pierre-Louis ESCOUFLAIRE

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