Support compile-only dependencies

[Nikratio]

I have a pkgconfig dependency for which I only need the headers - I do not want to link against the shared library. I tried to accomplish this with:

libfuse_dep = dependency('fuse3', version: '>=3.5.0')
fuse_headers = include_directories(libfuse_dep.get_pkgconfig_variable('includedir'))
# ...
executable('foo', 'foo.c', include_directories: [fuse_headers]

Unfortunately that did not work, the compile command did not include the include directory.

Bug or feature? I suspect that include_directories is not intended for absolute paths - but is there another solution?

$ meson --version
0.49.2

[dcbaker]

You want:

executable(
  'foo',
  'foo.c',
  dependencies : dep.partial_dependency(includes : true),
)

https://mesonbuild.com/Reference-manual.html#dependency-object

[Nikratio]

Thank you!

[Nikratio]

Hmm. It doesn't seem to work:

executable('readahead', 'readahead.cpp', 'readahead_main.cpp', 'common.cpp',
           dependencies: [ boost_dep, libfuse_dep.partial_dependency(includes: true) ],
           install: false)

gives me:

$ ninja kernel_read_tracing/readahead
[1/3] Compiling C++ object 'kernel_re...@readahead@exe/readahead_main.cpp.o'.
FAILED: kernel_read_tracing/ece328b@@readahead@exe/readahead_main.cpp.o 
c++ -Ikernel_read_tracing/ece328b@@readahead@exe -Ikernel_read_tracing -I../kernel_read_tracing -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -g -D_REENTRANT -DHAVE_CONFIG_H -D_GNU_SOURCE -Wall -Wextra -Wno-sign-compare -Wconversion -Wmissing-declarations -Wwrite-strings -Wno-unused-function -fno-strict-aliasing -Wno-unused-result  -MD -MQ 'kernel_read_tracing/ece328b@@readahead@exe/readahead_main.cpp.o' -MF 'kernel_read_tracing/ece328b@@readahead@exe/readahead_main.cpp.o.d' -o 'kernel_read_tracing/ece328b@@readahead@exe/readahead_main.cpp.o' -c ../kernel_read_tracing/readahead_main.cpp
In file included from ../kernel_read_tracing/readahead.hpp:10,
                 from ../kernel_read_tracing/readahead_main.cpp:13:
../kernel_read_tracing/../fs/readahead.hpp:19:10: fatal error: fuse_lowlevel.h: No such file or directory
 #include <fuse_lowlevel.h>
          ^~~~~~~~~~~~~~~~~
compilation terminated.
[...]

If I change this to:

executable('readahead', 'readahead.cpp', 'readahead_main.cpp', 'common.cpp',
           dependencies: [ boost_dep, libfuse_dep ],
           install: false)

then it works:

$ ninja -v kernel_read_tracing/readahead 
[0/1] /usr/bin/meson --internal regenerate /home/nikratio/consulting/valve/steamfs /home/nikratio/consulting/valve/steamfs/build --backend ninja
The Meson build system
Version: 0.49.2
[...]
[1/4] c++ -Ikernel_read_tracing/ece328b@@readahead@exe -Ikernel_read_tracing -I../kernel_read_tracing -I/usr/include/fuse3 -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -g -D_REENTRANT -DHAVE_CONFIG_H -D_GNU_SOURCE -Wall -Wextra -Wno-sign-compare -Wconversion -Wmissing-declarations -Wwrite-strings -Wno-unused-function -fno-strict-aliasing -Wno-unused-result  -MD -MQ 'kernel_read_tracing/ece328b@@readahead@exe/readahead.cpp.o' -MF 'kernel_read_tracing/ece328b@@readahead@exe/readahead.cpp.o.d' -o 'kernel_read_tracing/ece328b@@readahead@exe/readahead.cpp.o' -c ../kernel_read_tracing/readahead.cpp

(this includes the -I/usr/include/fuse3)

Am I missing something?

[Nikratio]

The problem is the same with Meson 0.55.0 (the reference manual says something about this not working right until v 0.50.1).

[dcbaker]

This looks like it might be a bug. is your project available somewhere that I could test it?

[Nikratio]

Here is a minimal example:

$ cat meson.build 
project('foo', ['cpp', 'c'], version: '0.1',
        meson_version: '>= 0.51',
        default_options: [ 'buildtype=debugoptimized',
                           'warning_level=2' ])
cc = meson.get_compiler('cpp')
libfuse_dep = dependency('fuse3', version: '>=3.5.0')
libfuse_headers = libfuse_dep.partial_dependency(includes: true)
executable('main', 'main.cpp', dependencies: libfuse_headers)

$ cat main.cpp 
#include <cstdio>
#include <fuse_lowlevel.h>

int main(int argc, char** argv) {
    printf("sizeof(fuse_ino_t): %d\n", (int) sizeof(fuse_ino_t));
    return 0;
}

Repro:

$ md build
$ cd build
$ meson ..
The Meson build system
Version: 0.55.0
Source dir: /home/nikratio/in-progress/mesonbug
Build dir: /home/nikratio/in-progress/mesonbug/build
Build type: native build
Project name: foo
Project version: 0.1
C compiler for the host machine: cc (gcc 8.3.0 "cc (Debian 8.3.0-6) 8.3.0")
C linker for the host machine: cc ld.bfd 2.31.1
C++ compiler for the host machine: c++ (gcc 8.3.0 "c++ (Debian 8.3.0-6) 8.3.0")
C++ linker for the host machine: c++ ld.bfd 2.31.1
Host machine cpu family: x86_64
Host machine cpu: x86_64
Found pkg-config: /usr/bin/pkg-config (0.29)
Run-time dependency fuse3 found: YES 3.7.0
Build targets in project: 1

Found ninja-1.8.2 at /usr/bin/ninja

$ ninja
[1/2] Compiling C++ object main.p/main.cpp.o
FAILED: main.p/main.cpp.o 
c++ -Imain.p -I. -I.. -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -Wextra -O2 -g -MD -MQ main.p/main.cpp.o -MF main.p/main.cpp.o.d -o main.p/main.cpp.o -c ../main.cpp
../main.cpp:2:10: fatal error: fuse_lowlevel.h: No such file or directory
 #include <fuse_lowlevel.h>
          ^~~~~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: subcommand failed.

[Nikratio]

...and:

$ cat /usr/lib/x86_64-linux-gnu/pkgconfig/fuse3.pc 
prefix=/usr
libdir=${prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include

Name: fuse3
Description: Filesystem in Userspace
Version: 3.7.0
Libs: -L${libdir} -lfuse3 -lpthread
Libs.private: -ldl -pthread -lrt
Cflags: -I${includedir}/fuse3

[Nikratio]

libfuse also uses meson: https://github.com/libfuse/libfuse/blob/master/meson.build

[dcbaker]

Not a regression, but a legitimate bug. The InternalDependency type has a separate field for includes, while ExternalDependencies store all compile args mixed together as a single list. I'm not exactly clear how to solve this as a whole. For pkg-config this is relatively easy since there's --cflags-only-I and --cflags-only-other. For other dependencies this is probably going to be painful.

In the short term using dep.partial_dependency(compile_args : true) will add the necessary -I flags.

sigh for bugs.

[dcbaker]

I'm removing this from the milestone. This is probably going to be a pretty invasive fix.