gnome: make sure the target build directory is passed first for linking

determine_rpath_dirs() can return paths to external dependencies not
in the build dir and passing them first as a link path leads to
g-ir-scanner for example linking against the already installed library
instead of the just built one.

This was reported in g-i: https://gitlab.gnome.org/GNOME/gobject-introspection/issues/272
and comes up quite often when a library adds some new symbols which aren't present in the
system library, which then makes linking fail.

The first place where the order is changed is _scan_gir_targets(), which looks like an unintentional
change in the refactoring in 8377ea45aa

The second place in _get_link_args() has always been that way and only the rpath order is changed,
but it looks to me as if the same rules should apply here too.

mesonbuild/modules/gnome.py

@@ -299,6 +299,9 @@ class GnomeModule(ExtensionModule):
         if isinstance(lib, build.SharedLibrary):
             libdir = os.path.join(state.environment.get_build_dir(), state.backend.get_target_dir(lib))
             link_command.append('-L' + libdir)
+            if include_rpath:
+                link_command.append('-Wl,-rpath,' + libdir)
+            depends.append(lib)
             # Needed for the following binutils bug:
             # https://github.com/mesonbuild/meson/issues/1911
             # However, g-ir-scanner does not understand -Wl,-rpath
@@ -308,9 +311,6 @@ class GnomeModule(ExtensionModule):
                 link_command.append('-L' + d)
                 if include_rpath:
                     link_command.append('-Wl,-rpath,' + d)
-            if include_rpath:
-                link_command.append('-Wl,-rpath,' + libdir)
-            depends.append(lib)
         if gir_has_option(self.interpreter, '--extra-library') and use_gir_args:
             link_command.append('--extra-library=' + lib.name)
         else:
@@ -553,6 +553,11 @@ class GnomeModule(ExtensionModule):
                     libname = girtarget.get_basename()
                 else:
                     libname = os.path.join("@PRIVATE_OUTDIR_ABS_%s@" % girtarget.get_id(), girtarget.get_filename())
+                ret += ['--library', libname]
+                # need to put our output directory first as we need to use the
+                # generated libraries instead of any possibly installed system/prefix
+                # ones.
+                ret += ["-L@PRIVATE_OUTDIR_ABS_%s@" % girtarget.get_id()]
                 # Needed for the following binutils bug:
                 # https://github.com/mesonbuild/meson/issues/1911
                 # However, g-ir-scanner does not understand -Wl,-rpath
@@ -560,11 +565,6 @@ class GnomeModule(ExtensionModule):
                 for d in state.backend.determine_rpath_dirs(girtarget):
                     d = os.path.join(state.environment.get_build_dir(), d)
                     ret.append('-L' + d)
-                ret += ['--library', libname]
-                # need to put our output directory first as we need to use the
-                # generated libraries instead of any possibly installed system/prefix
-                # ones.
-                ret += ["-L@PRIVATE_OUTDIR_ABS_%s@" % girtarget.get_id()]
 
         return ret
 

test cases/frameworks/28 gir link order 2/meson-sample.c

@@ -0,0 +1,42 @@
+#include "meson-sample.h"
+
+struct _MesonSample {
+  GObject parent_instance;
+};
+
+G_DEFINE_TYPE (MesonSample, meson_sample, G_TYPE_OBJECT)
+
+/**
+ * meson_sample_new:
+ *
+ * Allocates a new #MesonSample.
+ *
+ * Returns: (transfer full): a #MesonSample.
+ */
+MesonSample *
+meson_sample_new (void)
+{
+  return g_object_new (MESON_TYPE_SAMPLE, NULL);
+}
+
+static void
+meson_sample_class_init (MesonSampleClass *klass)
+{
+}
+
+static void
+meson_sample_init (MesonSample *self)
+{
+}
+
+/**
+ * meson_sample_print_message:
+ * @self: a #MesonSample.
+ *
+ * Prints a message.
+ */
+void
+meson_sample_print_message (MesonSample *self)
+{
+  g_return_if_fail (MESON_IS_SAMPLE (self));
+}

test cases/frameworks/28 gir link order 2/meson-sample.h

@@ -0,0 +1,17 @@
+#ifndef MESON_SAMPLE_H
+#define MESON_SAMPLE_H
+
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define MESON_TYPE_SAMPLE (meson_sample_get_type())
+
+G_DECLARE_FINAL_TYPE (MesonSample, meson_sample, MESON, SAMPLE, GObject)
+
+MesonSample *meson_sample_new           (void);
+void         meson_sample_print_message (MesonSample *self);
+
+G_END_DECLS
+
+#endif /* MESON_SAMPLE_H */

test cases/frameworks/28 gir link order 2/meson.build

@@ -0,0 +1,35 @@
+project('gir link order 2', 'c')
+
+if not dependency('gobject-2.0', required : false).found()
+  error('MESON_SKIP_TEST gobject not found.')
+endif
+
+gnome = import('gnome')
+gobject = dependency('gobject-2.0')
+
+# This builds a dummy libsample under samelibname that's not really used
+subdir('samelibname')
+
+# This builds the real libsample
+meson_sample_sources = ['meson-sample.c', 'meson-sample.h']
+meson_sample_lib = shared_library(
+  'sample',
+  sources : meson_sample_sources,
+  dependencies : [gobject],
+  link_with: [samelibname],
+  install : false,
+)
+
+# g-ir-scanner should get the linker paths in the right order so it links first
+# against the target libsample and not the dummy one that's just a dependency
+# https://github.com/mesonbuild/meson/pull/5423
+gnome.generate_gir(
+  meson_sample_lib,
+  sources : meson_sample_sources,
+  nsversion : '1.0',
+  namespace : 'Meson',
+  symbol_prefix : 'meson',
+  identifier_prefix : 'Meson',
+  install : false,
+  build_by_default: true,
+)

test cases/frameworks/28 gir link order 2/samelibname/meson.build

@@ -0,0 +1,5 @@
+samelibname = shared_library(
+  'sample',
+  sources : [],
+  install : false,
+)