Hi,

I'm running into compile errors when I'm adding a function to tools/pdbgen/pdb/image.pdb:

undefined reference to 'gimp_image_detach_parasite' undefined reference to 'gimp_image_get_parasite_list' undefined reference to 'gimp_image_get_parasite'

Delving deeper into this, I'm finding two function: - gimp_image_parasite_list()
- gimp_image_get_parasite_list()

According to a comment in libgimp/gimpimage.c, the version without the "get" in the name is deprecated and the one with the "get" should be used instead. The version without "get" is implemented here by calling the one with "get". However, in tools/pdbgen/pdb/image.pdb, the version with "get" is implemented by calling the one without "get". This seems a bit circular to me.

Something seems to be strange with the parasite functions... everything compiles fine when I get the source straight from git, but starts to break when I add functions to image.pdb.

So my question is: am I doing something wrong by adding functions to image.pdb, or is there actually something wrong with the parasite functions?

The changes I'm making to image.pdb are: - mark image_get_filename deprecated - mark image_set_filename deprecated - change description of image_get_uri - add image_set_uri
- add image_get_imported_uri
- add image_get_exported_uri

The error output when compiling:

make[4]: Entering directory `/mnt/lincoln/d3/gimp/source/gimp/plug-ins/script-fu' CC script-fu.o
CC script-fu-console.o
CC script-fu-eval.o
CC script-fu-interface.o
CC script-fu-text-console.o
CC script-fu-script.o
CC script-fu-scripts.o
CC script-fu-server.o
CC scheme-wrapper.o
CCLD script-fu
/mnt/lincoln/d3/gimp/source/gimp/libgimp/.libs/libgimp-2.0.so: undefined reference to `gimp_image_detach_parasite' /mnt/lincoln/d3/gimp/source/gimp/libgimp/.libs/libgimp-2.0.so: undefined reference to `gimp_image_get_parasite_list' /mnt/lincoln/d3/gimp/source/gimp/libgimp/.libs/libgimp-2.0.so: undefined reference to `gimp_image_get_parasite' collect2: ld returned 1 exit status
make[4]: *** [script-fu] Error 1
make[4]: Leaving directory
`/mnt/lincoln/d3/gimp/source/gimp/plug-ins/script-fu'

Eric

Thanks, Bill. That makes sense. Let's see if I understand this correctly:

app/core/gimpimage.c defines the function gimp_image_parasite_list, which actually implements the functionality of getting a list of parasites.

libgimp/gimpimage.c also defines a function called gimp_image_parasite_list, which tries to retrieve a list of parasites; this is what should be used by the plugins. However, this function tries to call a function called gimp_image_get_parasite_list, which doesn't exist. Hence the "undefined references" I'm getting.

tools/pdbgen/pdb/image.pdb defines a function called gimp_image_get_parasite_list, which calls the function gimp_image_parasite_list. I assume this is supposed to reference the version in app/core/gimpimage.c

The thing I don't understand is how this can possibly compile at all? I'm only getting the errors if I add functions to image.pdb. If I leave image.pdb as it comes from git, everything compiles.

The other thing I'm not sure about is whether the code I described above can even work. Can there be functions with the same name defined in app/core, in libgimp, and in pdb?

Thanks, Eric

On 03/13/2011 12:24 PM, Bill Skaggs wrote:

Pdbgen is part of the gimp application core. Libgimp is an interface library designed to
be used by plug-ins -- it is not and cannot be used inside the core. The functions that
can be used inside the core are documented at http://developer.gimp.org/api/2.0/app/index.html . In many cases they correspond pretty closely to libgimp functions, but the function names
are sometimes different, and the arguments are almost always different.

-- Bill

Thanks, Bill. I finally figured it out. At the bottom of tools/pdbgen/pdb/image.pdb, a hard-coded subset of the @proc array is passed as the series of functions to add to the library. By adding new functions, the bottom ones were no longer included, and so resulted in unresolved references.

I will include a couple of lines of comments that explain what is going on in the patch I will be submitting. I should also submit a patch for the README_NEW_PDB_PROC document to include this information in the documentation...

Eric

On 03/14/2011 01:17 PM, Bill Skaggs wrote:

It compiles because Gimp plug-ins (unlike PhotoShop plug-ins) are separate executables, which
communicate with the main Gimp app via a shared memory channel. As separate executables,
they are compiled separately and don't necessarily need to avoid function namespace conflicts with
the main app. (Although in my opinion it would be better design to avoid such conflicts.)

The libgimp function gimp_image_get_parasite_list is actually just the C hook for the function
image_get_parasite_list_invoker, whose autogenerated source code you can find in app/pdb/image_cmds.c. The PDB actually consists of a large set of "invoker" functions
of that sort -- libgimp is simply the C language binding that C plug-ins use to access the
PDB. Other languages such as Python and Ruby have their own bindings -- the function of
a binding is to transform a native language command into a call to one of the invoker functions
that belong to the PDB.

(Libgimp also contains some utility functions that are useful for C plug-ins but don't involve
the PDB, but that doesn't affect the main point.)

-- Bill