intercept open does not work

[markus2330]

When doing what the example says, intercept does not intercept (on debian jessie):

$ kdb export /preload/open ini
~\/testfile = ~/testreplacement
$ LD_PRELOAD=~build/lib/libelektraintercept.so cat ~/testfile
testfile

open is correctly intercepted, the problem seems to be the matching with ~, maybe zsh has some different behaviour? Can you also try kdb export? Giving full paths everything works.

[markus2330]

And it has compile warnings:

src/bindings/intercept/intercept.c:221:14: warning: ISO C forbids conversion of object pointer to function pointer type [-Wpedantic]
  orig_open = (orig_open_f_type)dlsym (RTLD_NEXT, "open");
              ^
src/bindings/intercept/intercept.c: In function ‘open64’:
src/bindings/intercept/intercept.c:259:16: warning: ISO C forbids conversion of object pointer to function pointer type [-Wpedantic]
  orig_open64 = (orig_open_f_type)dlsym (RTLD_NEXT, "open64");
                ^

[tom-wa]

thomas@Skipper ~ % echo $SHELL
/bin/zsh
thomas@Skipper ~ % kdb export /preload ini
[open]
~\/.zshrc = ~/.zshrc-other
~\/.zshrc/readonly = 1
~\/testfile = ~/testreplacement
thomas@Skipper ~ % cat ~/testfile
cat: /home/thomas/testfile: Datei oder Verzeichnis nicht gefunden
thomas@Skipper ~ % cat ~/testreplacement
replacement
thomas@Skipper ~ % LD_PRELOAD=/usr/local/lib/libelektraintercept.so cat ~/testfile
replacement

[markus2330]

kdb export /preload ini seems to be identical, so maybe it is a zsh version thing zsh 5.0.7 (x86_64-pc-linux-gnu)? Has libelektraintercept.so problems when working from the build-folder? Do you have another idea? Can you write a shellrecorder test suite, it might be easier to reproduce this way.

Btw. libelektraintercept.so is a very generic name, what about changing it to libelektraintercept-open.so and libelektraintercept-getenv.so?

A small wrapper script such as scripts/elektrify-getenv.in would be nice, too.

[tom-wa]

just tried it on all my boxes (all running zsh), and for me it works on all.
but it seems like you have some custom expansion for ~ like in ~build ?
i'm running zsh 5.2 (x86_64-debian-linux-gnu)

for me even ~\/..\/.\/thomas\/.zshrc = ~/../.././home/thomas/./.zshrc-other works just fine

[tom-wa]

i've just built and installed it on a clean debian stable box running zsh 5.0.7 (i586-pc-linux-gnu)

thomas@Kowalski ~/libelektra/build
 % kdb export /preload ini
[open]
~\/.zshrc/readonly = 1
~\/testfile = ~/testreplacement
~\/..\/.\/thomas\/.zshrc = ~/../.././home/thomas/./.zshrc-other
thomas@Kowalski ~/libelektra/build
 % vim ~/preload.ini
thomas@Kowalski ~/libelektra/build
 % kdb export /preload ini
[open]
~\/testfile = ~/testreplacement
~\/..\/.\/thomas\/.zshrc = ~/../.././home/thomas/./.zshrc-other
thomas@Kowalski ~/libelektra/build
 % cat ~/testfile
testfile
thomas@Kowalski ~/libelektra/build
 % cat ~/testreplacement
testreplacement
thomas@Kowalski ~/libelektra/build
 % cat ~/.zshrc-other
zshrc-other
thomas@Kowalski ~/libelektra/build
 % LD_PRELOAD=/usr/local/lib/libelektraintercept.so cat ~/testfile
testreplacement
thomas@Kowalski ~/libelektra/build
 % LD_PRELOAD=/usr/local/lib/libelektraintercept.so cat ~/.zshrc
zshrc-other

[markus2330]

Seems to have nothing to do with zsh config (same problem in zsh -f) nor zsh itself (same problem in bash), but I can reproduce it on another machine too:

markusbyte% kdb set /preload/open/\~\\/testfile "~/testreplacement"
Using name user/preload/open/~\/testfile
Set string to ~/testreplacement
markusbyte% LD_PRELOAD=/home/markus/Projekte/Elektra/build/lib/libelektraintercept.so cat ~/testfile
testfile
markusbyte% kdb export /preload ini
[open]
~\/testfile = ~/testreplacement
markusbyte% cat testfile 
testfile
markusbyte% cat testreplacement 
testreplacement

markus@markusbyte:~> bash 
markus@markusbyte:~$ kdb set /preload/open/\~\\/testfile "~/testreplacement"
Using name user/preload/open/~\/testfile
Set string to ~/testreplacement
markus@markusbyte:~$ kdb export /preload ini
[open]
~\/testfile = ~/testreplacement
markus@markusbyte:~$ LD_PRELOAD=/home/markus/Projekte/Elektra/build/lib/libelektraintercept.so cat ~/testfile
testfile

I think the most likely problem is some typo in the example (I already fixed two problems), please try to source the example and write some shellrecorder tests.

[tom-wa]

i really can't reprocude the problem here. on none of my boxes.

thomas@Private ~ % kdb set /preload/open/\~\\/testfile "~/testreplacement"
Using name user/preload/open/~\/testfile
Create a new key user/preload/open/~\/testfile with string ~/testreplacement
thomas@Private ~ % kdb export /preload
[open]
~\/testfile = ~/testreplacement
thomas@Private ~ % echo testfile > ~/testfile
thomas@Private ~ % echo testreplacement > ~/testreplacement
thomas@Private ~ % LD_PRELOAD=/path/to/libelektraintercept.so cat ~/testfile
ERROR: ld.so: object '/path/to/libelektraintercept.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
testfile
thomas@Private ~ % LD_PRELOAD=/usr/local/lib/libelektraintercept.so cat ~/testfile                                           
testreplacement

[markus2330]

Ok, the problem is that the key /preload/open must exist which does on your machines (because you use ini as default), but does not when another default storage plugin is used.

Please update the example and add shell recorder tests.

[markus2330]

(and fix warnings), then we can close the issue

[markus2330]

I hope @sanssecours finds a solution for such problems, different behaviour in storage plugins is really a pain.

[tom-wa]

(and fix warnings), then we can close the issue

is it ok if i just use pragma to turn warnings off for those 2 lines ? it seems like the behaviour/use of dlsym is actually undefined behaviour according to the man page.

[markus2330]

There are other places that already fix the problem. You can use memcpy or a union.