Re: segfault when using freopen() after an ld preloaded wrapped fopen()

[Manuel Arriaga]

Hi Geert, all,

My name is Manuel Arriaga and I wrote libtrash -- 
http://www.m-arriaga.net/software/libtrash . libtrash is a piece of code 
which, when preloaded, implements a "trash can" under GNU/Linux.


> When working on a sandbox solution using the ld preload mechanism, I
> came accross a weird behaviour. When creating a wrapper for fopen() and
> freopen() (wrapped or non-wrapped) is later used, libc segfaults on all
> the subsequent calls that use the newly returned FILE stream.

The problem you describe is precisely the cause of the misbehaviour which was 
reported a few days ago concerning libtrash and mutt.

May I ask how you uncovered this problem? Exactly the same thing happens 
inside mutt (any recent version): the file is opened without problems using a 
preloaded fopen(), then freopened() (either through a wrapper or not), and, 
afterwards, a call to ftell() causes a segmentation fault. 

Using gdb I traced it down to line 63 of glibc-2.2.3/libio/ioseekoff.c 
(that's the version I'm using). From that point on, I'm clueless.

Can anyone offer any advice/help/confirmation?

Best regards,

Manuel Arriaga