Re: lt_dlopen an uninstalled library
On Thu, 25 Nov 2021, ilya Basin wrote: Loading modules is an extremely security-sensitive issue so it makes sense to require that the specified path be absolute I agree. Actually I haven't told the whole truth. My goal was to [mis]use libtool to load dynamically a regular library that is supposed to be in /usr/lib/ on Unix and at the same folder as .exe on Windows. The reason I don't link with it is my library depends on some other libraries that are not in the search path and my executable loads them first, then loads my library. This is why a wrapper script would solve it. Years ago, Gary V. Vaughan (a key libtool developer) suggested to me that dlopen() is quite portable across Unix-like systems (even Apple's OS X) and that libltdl is not really necessarily needed in order to load dynamic modules/modules. This leaves Microsoft Windows for which it it is relatively easy to use its similar facilities via LoadLibrary()/FreeLibrary(). It is true that libltdl will help on systems where library dependencies do not work properly, or where special compiler options must be used, and it can be used to emulate a loadable module in static builds. Libtool is exceedingly helpful when it is desired to be able to support static builds and it also helps for compiling shared libraries (DLLs) under Microsoft Windows. So it is worth considering using dlopen() directly. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Re: lt_dlopen an uninstalled library
> Loading modules is an extremely security-sensitive issue so it makes sense to > require that the specified path be absolute I agree. Actually I haven't told the whole truth. My goal was to [mis]use libtool to load dynamically a regular library that is supposed to be in /usr/lib/ on Unix and at the same folder as .exe on Windows. The reason I don't link with it is my library depends on some other libraries that are not in the search path and my executable loads them first, then loads my library. This is why a wrapper script would solve it. It would be gread if an option existed in libtool to force a wrapper script even if we don't link with any uninstalled libraries. On 25.11.2021 2:15, Bob Friesenhahn wrote: > On Thu, 25 Nov 2021, ilya Basin wrote: > >> Hi Bob. I configured the GM build with '--with-modules', ran `make check` >> successfully. Then truncated the built .so files inside the 'coders/' dir to >> break it. Then reproduced the failure in gdb >> >> [il@reallin GM]$ export >> MAGICK_CONFIGURE_PATH='/home/il/builds/GM/config:/home/il/builds/GM/config' >> [il@reallin GM]$ export >> MAGICK_CODER_MODULE_PATH='/home/il/builds/GM/coders' >> [il@reallin GM]$ gdb --args ./tests/.libs/lt-constitute -storagetype char >> /home/il/builds/GM/tests/input_truecolor.miff bgr >> >> So it turned out that the test program relies on the full path to the >> modules dir passed to the program and it calls lt_dlopen() with the full >> path. I guess I'll have to set the test environment in Makefile.am. Thanks. > > It is interesting that this is what was causing problems for you. Loading > modules is an extremely security-sensitive issue so it makes sense to require > that the specified path be absolute, or written like ./foo.la. > > Regardless, GraphicsMagick does some things differently than perhaps the > original libtool/libltdl objectives since it tries not to be too dependent on > libltdl and it has its own module loader smarts. > > Bob
