[ESS-bugs] ESS bug : "?for" command makes Emacs session freeze

[Jean-Loup Tastet]

OS : Fedora 19 x86_64
R version : 3.0.2
ESS version : 12.09 (Fedora repositories version)
Emacs version : 24.3.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.8.2)

Abstract : entering "?for" at command line in ESS causes Emacs to
freeze.

Reproductible : always.

Steps to reproduce :
1 - Open Emacs ;
2 - Start ESS session with M-x R ;
3 - Type "?for" at command line.

Actual result : Emacs freezes. Not only ESS, but all inferior processes
running within the same instance of Emacs. Data saved using the
save.session() function in "session" package is lost.

Expected result : R displays help about the "for" loop keyword.

Severity : data saved using the save.session() function in the "session"
library was lost, but not data saved when exiting R using the q()
function. Other Emacs inferior processes might also have experienced
data loss.

Note : this command also fails with R alone, but in another way : by
printing "+" and waiting for another input from the user, instead of
displaying any help. But nothing freezes.

Note 2 : when opening a new session in the same directory, Emacs froze
once when entering the ls() command. This was not reproductible.