Failed to build a simple gtk-fortran example: how to link with gtk-4-fortran?

[vmagnin]

I have created a small repository with the example I am trying to build as an fpm project:
https://github.com/vmagnin/gtkzero_fpm
It is the gtkzero_gapp.f90 available in the gtk-fortran gtk4 branch: it just opens an empty GTK 4 window. As the original file contains the main program and a handlers module, I have put that module in src/handlers.f90. The main program has been renamed: app/main.f90.

My fpm version is 0.2.0 alpha. I have tried adding link = "gtk-4-fortran" in the [build] section of the fpm.toml file, but it does not change anything.

$ fpm build --flag '$(pkg-config --cflags --libs gtk-4-fortran)'
Unable to find source for module dependency: "gtk" used by "app/main.f90"
ERROR STOP 1

Error termination. Backtrace:
#0  0x7f559b678820 in ???
#1  0x7f559b679379 in ???
#2  0x7f559b67ab02 in ???
#3  0x55e89918f6a5 in __fpm_MOD_cmd_build
        at ././src/fpm.f90:260
#4  0x55e89917944f in MAIN__
        at app/main.f90:26
#5  0x55e89917944f in main
        at app/main.f90:9

Same error if I replace the apostrophes by double quotes.

This is the output of the pkg-config command on my machine:

$ pkg-config --cflags --libs gtk-4-fortran
-rdynamic -mfpmath=sse -msse -msse2 -pthread -I/usr/local/include/gtk-4-fortran -I/usr/include/gtk-4.0 -I/usr/include/gio-unix-2.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/fribidi -I/usr/include/harfbuzz -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/uuid -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/graphene-1.0 -I/usr/lib/x86_64-linux-gnu/graphene-1.0/include -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -Xlinker -R/usr/local/lib -lgtk-4-fortran -lgtk-4 -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -lgdk_pixbuf-2.0 -lcairo-gobject -lcairo -lvulkan -lgraphene-1.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0

The gtk-fortran modules are here:

$ ls /usr/local/include/gtk-4-fortran
cairo.mod          g.mod                 gtk_hl_button.mod     gtk_hl_entry.mod     gtk_hl_spin_slider.mod  handlers_gtk_fortran.mod
gdk_events.mod     graphene.mod          gtk_hl_chooser.mod    gtk_hl_infobar.mod   gtk_hl_tree.mod         pango.mod
gdk.mod            gsk.mod               gtk_hl_combobox.mod   gtk_hl_misc.mod      gtk.mod                 plplot_extra.mod
gdk_pixbuf_hl.mod  gtk_draw_hl.mod       gtk_hl_container.mod  gtk_hl.mod           gtk_os_dependent.mod    unix_print.mod
gdk_pixbuf.mod     gtk_hl_assistant.mod  gtk_hl_dialog.mod     gtk_hl_progress.mod  gtk_sup.mod

[awvwgk]

External module files have to declared explicitly, see here. In this case it would require an additional entry in the build section:

[build]
link = "gtk-4-fortran"
external-modules = ["gtk", "g"]

[vmagnin]

In this case it would require an additional entry in the build section:

My fpm does not like that new line :-(

$ fpm build --flag "$(pkg-config --cflags --libs gtk-4-fortran)"
Key external-modules is not allowed in [build]
ERROR STOP 1

Error termination. Backtrace:
#0  0x7f641f428820 in ???

Perhaps not yet in fpm 0.2.0 ?

[awvwgk]

You're right, it was added with #438 but hasn't been released yet.

[awvwgk]

This might be resolved with the freshly released fpm version 0.3.0

[vmagnin]

Thanks @awvwgk for the information,
I will try when I have some time and report here the result.

[vmagnin]

@awvwgk
I have just installed fpm 0.3.0 alpha (Ubuntu 21.04).
It's better but the linking fails with the same little test project (https://github.com/vmagnin/gtkzero_fpm):

$ fpm build --flag '$(pkg-config --cflags --libs gtk-4-fortran)'
 + mkdir -p build/dependencies
 + mkdir -p build/gfortran_4E42016360FFAE8D/gtkzero_fpm
 + gfortran -c test/check.f90 $(pkg-config --cflags --libs gtk-4-fortran) -J build/gfortran_4E42016360FFAE8D/gtkzero_fpm -I build/gfortran_4E42016360FFAE8D/gtkzero_fpm  -o build/gfortran_4E42016360FFAE8D/gtkzero_fpm/test_check.f90.o
 + gfortran -c ././src/handlers.f90 $(pkg-config --cflags --libs gtk-4-fortran) -J build/gfortran_4E42016360FFAE8D/gtkzero_fpm -I build/gfortran_4E42016360FFAE8D/gtkzero_fpm  -o build/gfortran_4E42016360FFAE8D/gtkzero_fpm/src_handlers.f90.o
 + ar -rs build/gfortran_4E42016360FFAE8D/gtkzero_fpm/libgtkzero_fpm.a build/gfortran_4E42016360FFAE8D/gtkzero_fpm/src_handlers.f90.o
ar: création de build/gfortran_4E42016360FFAE8D/gtkzero_fpm/libgtkzero_fpm.a
 + gfortran -c app/main.f90 $(pkg-config --cflags --libs gtk-4-fortran) -J build/gfortran_4E42016360FFAE8D/gtkzero_fpm -I build/gfortran_4E42016360FFAE8D/gtkzero_fpm  -o build/gfortran_4E42016360FFAE8D/gtkzero_fpm/app_main.f90.o
 + mkdir -p build/gfortran_4E42016360FFAE8D/app/
 + gfortran  $(pkg-config --cflags --libs gtk-4-fortran) -J build/gfortran_4E42016360FFAE8D/gtkzero_fpm -I build/gfortran_4E42016360FFAE8D/gtkzero_fpm  build/gfortran_4E42016360FFAE8D/gtkzero_fpm/app_main.f90.o build/gfortran_4E42016360FFAE8D/gtkzero_fpm/libgtkzero_fpm.a -lgtk-4-fortran -o build/gfortran_4E42016360FFAE8D/app/gtkzero_fpm
/usr/bin/ld: build/gfortran_4E42016360FFAE8D/gtkzero_fpm/app_main.f90.o: undefined reference to symbol 'gtk_application_new'
/usr/bin/ld : /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/libgtk-4.so : erreur lors de l'ajout de symboles : DSO missing from command line
collect2: error: ld returned 1 exit status
 <ERROR> Compilation failed for object "gtkzero_fpm"
STOP 1

Note that if I type the following command, it compiles and runs:

$ gfortran src/handlers.f90 app/main.f90 $(pkg-config --cflags --libs gtk-4-fortran)

[awvwgk]

The problem is that you are adding the libs with the --flag command, and they will end up in-front of the objects in the link line.

You probably have to add the output of pkg-config --libs gtk-4-fortran to the build.link entry in the package manifest, rather than using it with the --flag switch.

[vmagnin]

Thanks Sebastian @awvwgk

I have separated the --cflags and --libs parts of the pkg-config command. I am now using the following command:

$  fpm build --flag '$(pkg-config --cflags gtk-4-fortran) -Xlinker -R/usr/local/lib'

In the fpm.toml, I first tried:

link = "gtk-4 pangocairo-1.0 pango-1.0 harfbuzz gdk_pixbuf-2.0 cairo-gobject cairo vulkan graphene-1.0 gio-2.0 gobject-2.0 glib-2.0 gtk-4-fortran"

The problem is that on the compilation command lines, only the first library is prefixed with -l (-lgtk-4 pangocairo-1.0 pango-1.0 harfbuzz gdk_pixbuf-2.0 cairo-gobject cairo vulkan graphene-1.0 gio-2.0 gobject-2.0 glib-2.0 gtk-4-fortran)
I was therefore obliged to add -l in front of all the other libraries:

link = "gtk-4 -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -lgdk_pixbuf-2.0 -lcairo-gobject -lcairo -lvulkan -lgraphene-1.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lgtk-4-fortran"

In that case, the build is OK with:

$  fpm build --flag '$(pkg-config --cflags gtk-4-fortran) -Xlinker -R/usr/local/lib'

But if I run:

$ fpm run
 + mkdir -p build/gfortran_2A42023B310FA28D/gtkzero_fpm
 + gfortran -c test/check.f90 -Wall -Wextra -Wimplicit-interface -fPIC -fmax-errors=1 -g -fcheck=bounds -fcheck=array-temps -fbacktrace -fcoarray=single -J build/gfortran_2A42023B310FA28D/gtkzero_fpm -I build/gfortran_2A42023B310FA28D/gtkzero_fpm  -o build/gfortran_2A42023B310FA28D/gtkzero_fpm/test_check.f90.o
 + gfortran -c ./src/handlers.f90 -Wall -Wextra -Wimplicit-interface -fPIC -fmax-errors=1 -g -fcheck=bounds -fcheck=array-temps -fbacktrace -fcoarray=single -J build/gfortran_2A42023B310FA28D/gtkzero_fpm -I build/gfortran_2A42023B310FA28D/gtkzero_fpm  -o build/gfortran_2A42023B310FA28D/gtkzero_fpm/src_handlers.f90.o
./src/handlers.f90:7:7:

	7 |   use gtk, only: gtk_window_set_default_size, gtk_window_set_title, &
	  |       1
Fatal Error: Cannot open module file ‘gtk.mod’ for reading at (1): Aucun fichier ou dossier de ce type
compilation terminated.
 <ERROR> Compilation failed for object "src_handlers.f90.o"
STOP 1

Finally it runs successfully if I use the --flag options with fpm run:

$ fpm run --flag '$(pkg-config --cflags gtk-4-fortran) -Xlinker -R/usr/local/lib'

[awvwgk]

The problem is that on the compilation command lines, only the first library is prefixed with -l (-lgtk-4 pangocairo-1.0 pango-1.0 harfbuzz gdk_pixbuf-2.0 cairo-gobject cairo vulkan graphene-1.0 gio-2.0 gobject-2.0 glib-2.0 gtk-4-fortran)

build.link takes a list of strings or a single string as shortcut for a list with one entry:

build.link = [
  "gtk-4",
  "pangocairo-1.0",
  "pango-1.0",
  "harfbuzz",
  "gdk_pixbuf-2.0",
  "cairo-gobject",
  "cairo",
  "vulkan",
  "graphene-1.0",
  "gio-2.0",
  "gobject-2.0",
  "glib-2.0",
  "gtk-4-fortran",
]

It's quite a lot of libraries to specify explicitly, unfortunately.

[vmagnin]

OK @awvwgk , I should have thought that it must be a list like in my external-modules = ["gtk", "g"] line.

So, now everything is OK with those commands:

$ fpm build --flag '$(pkg-config --cflags gtk-4-fortran) -Xlinker -R/usr/local/lib'

and

$  fpm run --flag '$(pkg-config --cflags gtk-4-fortran) -Xlinker -R/usr/local/lib'

But I don't understand why I am obliged to use --flag with fpm run... (see my previous message for the error message if I don't add the flags). If I go into the build directory and I click on the executable it runs fine. So what does fpm run does?

[vmagnin]

Note also that all the libraries are not needed for all programs, that's just for the general case.
For that small example, we just need:

link = [
  "gtk-4",
  "gio-2.0",
  "gobject-2.0",
  "glib-2.0",
  "gtk-4-fortran",
]

[awvwgk]

fpm is stateless, if you use fpm run it will first invoke fpm build to make sure the binary is up-to-date, to select the binary the command line arguments are hashed, therefore every fpm command has to know the full list of flags to select the right build.

Better pkg-config support would resolve this issue of having to use --flag mostly, maybe something like

[dependencies]
gtk-4-fortran.pkg-config = "gtk-4-fortran"

could be an option.

[vmagnin]

Thanks for all!
I have added a How to use fpm to build a gtk-fortran project in the gtk-fortran wiki.