FLTK

[Mark Summerfield]

I'm just starting out with meson.

I can build 'hello.cpp' console app with no problem.

But I'd now like to create an FLTK app (on Linux).

I have locally installed FLTK in `~/opt/fltk13` and I have `fltk-config` (which works just like `pkg-config`) in my `PATH`.

How do I tell meson to use `fltk-config`?

Thanks.

[Eli Schwartz]

On 11/22/21 4:13 AM, 'Mark Summerfield' via The Meson Build System wrote:
> I'm just starting out with meson.
> I can build 'hello.cpp' console app with no problem.
> But I'd now like to create an FLTK app (on Linux).
> I have locally installed FLTK in `~/opt/fltk13` and I have `fltk-config`
> (which works just like `pkg-config`) in my `PATH`.

Unfortunately, fltk-config does NOT work just like pkg-config, that is
why pkg-config itself exists. :) The best long-term solution would be to
persuade upstream to implement this:

https://github.com/fltk/fltk/issues/22
https://www.fltk.org/str.php?L2180

> How do I tell meson to use `fltk-config`?

Since you don't have a proper pkg-config file, you'll need to jump
through a couple hoops:

fltk_config = find_program('fltk-config')

fltk_cflags = run_command(fltk_config, '--cflags', check:
true).stdout().strip()
fltk_libs = run_command(fltk_config, '--libs', check: true).stdout().strip()

fltk_dep = declare_dependency(compile_args: fltk_cflags, link_args:
fltk_libs)


--
Eli Schwartz

[Mark]

That got me a lot further, but I can't get the fltk 'hello world' to build (even though the test/demo works fine).

```

$ meson setup unix
The Meson build system
Version: 0.60.1
Source dir: /home/mark/app/cpp/hello-fltk
Build dir: /home/mark/app/cpp/hello-fltk/unix
Build type: native build
Project name: hello fltk
Project version: 0.1.0
C++ compiler for the host machine: c++ (gcc 9.3.0 "c++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0")
C++ linker for the host machine: c++ ld.bfd 2.34
Host machine cpu family: x86_64
Host machine cpu: x86_64
Program fltk-config found: YES (/home/mark/opt/bin/fltk-config)
Found pkg-config: /usr/bin/pkg-config (0.29.1)
Found CMake: /usr/bin/cmake (3.16.3)
Run-time dependency x11 found: YES
Build targets in project: 1

Found ninja-1.10.0 at /usr/bin/ninja

$ meson compile -C unix
ninja: Entering directory `/home/mark/app/cpp/hello-fltk/unix'
[2/2] Linking target hellofltk
FAILED: hellofltk
c++  -o hellofltk hellofltk.p/hello.cpp.o -Wl,--as-needed -Wl,--no-undefined -Wl,--start-group /home/mark/opt/fltk14/lib/libfltk.a /usr/lib/x86_64-linux-gnu/libX11.so -Wl,--end-group
/usr/bin/ld: /home/mark/opt/fltk14/lib/libfltk.a(Fl_X11_Window_Driver.o): undefined reference to symbol 'dlsym@@GLIBC_2.2.5'
/usr/bin/ld: /lib/x86_64-linux-gnu/libdl.so.2: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
```

Note that fltk is normally statically linked.

[Mark]

Sorry forgot to include my `meson.build`:

```

project('hello fltk', 'cpp', version: '0.1.0')

fltk_config = find_program('fltk-config')

fltk_include_dirs = run_command(fltk_config, '--includedir',
                    check: true).stdout().strip()
fltk_cxxflags = run_command(fltk_config, '--cxxflags',
              check: true).stdout().strip()
fltk_link_args = run_command(fltk_config, '--libs',
                 check: true).stdout().strip()
fltk_dep = declare_dependency(compile_args: fltk_cxxflags,
                  include_directories: fltk_include_dirs,
                  link_args: fltk_link_args)
x11_dep = dependency('X11')

executable('hellofltk', 'hello.cpp', dependencies: [fltk_dep, x11_dep])
```

[Dan Kegel]

fltk_config seems to have left out -ldl, try jamming that in.

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[Mark]

I'd be happy to try `-ldl` but don't know how to add that to my `meson.build`. I'm looking through the docs which I find v. frustrating.

[Mark]

I think I found how to add it so now my `meson.build` is:

```

project('hello fltk', 'cpp', version: '0.1.0')

fltk_config = find_program('fltk-config')
fltk_include_dirs = run_command(fltk_config, '--includedir', check: true).stdout().strip()
fltk_cxxflags = run_command(fltk_config, '--cxxflags', check: true).stdout().strip()
fltk_link_args = run_command(fltk_config, '--libs', check: true).stdout().strip()
fltk_dep = declare_dependency(compile_args: fltk_cxxflags,
                  include_directories: fltk_include_dirs,
                  link_args: fltk_link_args)

cc = meson.get_compiler('cpp')
dl_dep = cc.find_library('dl')

x11_dep = dependency('X11')

executable('hellofltk', 'hello.cpp', dependencies: [fltk_dep, dl_dep, x11_dep])
```

It still won't build but I think from the output that I need to add more dependencies, this time maybe on Xft.

[snip]

Anyway, thanks for your help.

[Eli Schwartz]

On 11/22/21 11:23 AM, 'Mark' wrote:
> It still won't build but I think from the output that I need to add
> more dependencies, this time maybe on Xft.

I took a look at the actual fltk-config program. It seems for some
strange reason you need to use both --libs and --ldflags, the latter
contains all the libs for the dependencies it needs.

I also made a terrible mistake before. You need to use .strip() on all
the outputs of run_command, to ensure that they get split on whitespace
and turned into arrays.

project('hello fltk', 'cpp', version: '0.1.0')

fltk_config = find_program('fltk-config')
fltk_include_dirs = run_command(fltk_config, '--includedir', check:

true).stdout().strip().split()

fltk_cxxflags = run_command(fltk_config, '--cxxflags', check:

true).stdout().strip().split()
fltk_link_args = run_command(fltk_config, '--ldflags', '--libs', check:
true).stdout().strip().split()

fltk_dep = declare_dependency(compile_args: fltk_cxxflags,
include_directories: fltk_include_dirs,
link_args: fltk_link_args)

cc = meson.get_compiler('cpp')

executable('hellofltk', 'hello.cpp', dependencies: [fltk_dep])


Again, if they just provided pkg-config files upstream then you wouldn't
need to struggle with this, it would just be:

fltk_dep = dependency('fltk')

and it would correctly figure out include directories, libs,
dependencies, everything all for you. Instead they have a non-standard
shell script which is confusing to use, and likely doesn't handle
cross-compiling correctly.


--
Eli Schwartz