On Mon, May 25, 2020 at 1:19 AM Stelian Ionescu sionescu@cddr.org wrote:
On Sun, 2020-05-24 at 21:57 +0200, Florian Margaine wrote:
Good morning cffi-devel,
I have been recently sending a bunch of pull requests:
Which are really the following issue:
- CFFI loads a static foreign library, either as :grovel-wrapper or
:system
- The image is dumped with the loaded library
- When restored, the runtime will try to reload those "shared"
libraries and fails because the path doesn't exist on the target system
Specifically for the 2nd one, CFFI provides a :c-file ASDF integration, which, when used with :static-program-op, will compile the C file into an object file (among others), load it as a foreign library, and statically link the object file with the program.
In order to make it possible to distribute this static-program-op output, we essentially need to close the foreign library (IOW unload it), or not load it to begin with, before dumping the image. That means tracking those. The 2nd PR I made, as sionescu pointed out, doesn't work because C- FILE code isn't aware of whether it's going to be used for static-program- op or not.So I can see 2 ways out of this:
- Either we make FOREIGN-LIBRARY-TYPE settable from the outside
(remember that CFFI-TOOLCHAIN is not in the CFFI package), which doesn't sound like the correct way to go to me?
- Or we add a CLOSE-ON-DUMP option, which we can use when registering
the library. (Btw, that means exposing the REGISTER-FOREIGN-LIBRARY symbol, but that sounds uncontroversial to me.)
I don't think either of those are a good idea because they're not solving the problem at its core: 1) the wrapper shared objects are loaded by absolute path and 2) the filesystem layout differs between host and target machine
To fix that you need to either
- keep the .so as they are, and have static-program-op output a
directory containing the output binary and all the wrappers, then fixup the wrapper paths so that the runtime finds the shared objects in their new location (might need to close them and have them re-opened on start). This is what most other dynamic language runtimes do (Perl, Python, etc...)
- statically link the wrapper: make the wrapper op also generate a
static archive (.a), then link to that in static-program-op
The static link is already what static-program-op is doing. The problem is that the foreign library is _also_ loaded as a shared library, and is restored when the image restores itself. Which fails with the wrong paths.
-- Stelian Ionescu a.k.a. fe[nl]ix Quidquid latine dictum sit, altum videtur.