gnome: Distinguish between internal and external linker flags

When an older version of the library being built is installed in the
same prefix as external dependencies, we have to be careful to construct
the linker or compiler command line. If a -L flag from external
dependencoes comes before a -L flag pointing to builddir, it is possible
for the linker to load older libraries from the installation prefix
instead of the newly built ones, which is likely to cause undefined
reference error.

Since the order of dependencies is not significant, we cannot expect
internal dependencies to appear before external dependencies when
recursively iterating the list of dependencies. To make it harder to
make mistakes, linker flags come from internal and external
dependencies are now stored in different order sets. Code using
_get_dependencies_flags are expected to follow the order when
constructing linker command line:

  1. Internal linker flags
  2. LDFLAGS set by users
  3. External linker flags

It is similar to what automake and libtool do for autotools projects.

9 files changed, 157 insertions, 0 deletions

diff --git a/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.c b/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.c
new file mode 100644
index 000000000..fae9c3832
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.c
@@ -0,0 +1,6 @@
+#include "fake-gthread.h"
+
+int fake_gthread_fake_function (void)
+{
+  return 7;
+}
diff --git a/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.h b/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.h
new file mode 100644
index 000000000..52b54727d
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/fake-gthread/fake-gthread.h
@@ -0,0 +1,6 @@
+#ifndef FAKE_GTHREAD_H
+#define FAKE_GTHREAD_H
+
+int fake_gthread_fake_function (void);
+
+#endif /* FAKE_GTHREAD_H */
diff --git a/test cases/frameworks/22 gir link order/fake-gthread/meson.build b/test cases/frameworks/22 gir link order/fake-gthread/meson.build
new file mode 100644
index 000000000..693e8e0ec
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/fake-gthread/meson.build
@@ -0,0 +1,12 @@
+fake_gthread_sources = ['fake-gthread.c', 'fake-gthread.h']
+fake_gthread_lib = shared_library(
+  'gthread-2.0',
+  sources : fake_gthread_sources,
+  install : false,
+)
+
+fake_gthread_includes = include_directories('.')
+fake_gthread = declare_dependency(
+  include_directories : fake_gthread_includes,
+  link_with : fake_gthread_lib,
+)
diff --git a/test cases/frameworks/22 gir link order/get-prgname/get-prgname.c b/test cases/frameworks/22 gir link order/get-prgname/get-prgname.c
new file mode 100644
index 000000000..356b45e1d
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/get-prgname/get-prgname.c
@@ -0,0 +1,8 @@
+#include "get-prgname.h"
+
+#include <glib.h>
+
+const char *get_prgname_get_name (void)
+{
+  return g_get_prgname ();
+}
diff --git a/test cases/frameworks/22 gir link order/get-prgname/get-prgname.h b/test cases/frameworks/22 gir link order/get-prgname/get-prgname.h
new file mode 100644
index 000000000..cb5118e7a
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/get-prgname/get-prgname.h
@@ -0,0 +1,6 @@
+#ifndef GET_PRGNAME_H
+#define GET_PRGNAME_H
+
+const char *get_prgname_get_name (void);
+
+#endif /* GET_PRGNAME_H */
diff --git a/test cases/frameworks/22 gir link order/get-prgname/meson.build b/test cases/frameworks/22 gir link order/get-prgname/meson.build
new file mode 100644
index 000000000..6a7489db4
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/get-prgname/meson.build
@@ -0,0 +1,13 @@
+get_prgname_sources = ['get-prgname.c', 'get-prgname.h']
+get_prgname_lib = shared_library(
+  'get-prgname',
+  sources : get_prgname_sources,
+  dependencies : [glib],
+  install : false,
+)
+
+get_prgname_includes = include_directories('.')
+get_prgname = declare_dependency(
+  include_directories : get_prgname_includes,
+  link_with : get_prgname_lib,
+)
diff --git a/test cases/frameworks/22 gir link order/meson-sample.c b/test cases/frameworks/22 gir link order/meson-sample.c
new file mode 100644
index 000000000..7c6442aa7
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/meson-sample.c
@@ -0,0 +1,48 @@
+#include "meson-sample.h"
+
+#include "get-prgname.h"
+#include "fake-gthread.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));
+
+  g_print ("Message: %s\n", get_prgname_get_name ());
+  g_print ("Message: %d\n", fake_gthread_fake_function ());
+}
diff --git a/test cases/frameworks/22 gir link order/meson-sample.h b/test cases/frameworks/22 gir link order/meson-sample.h
new file mode 100644
index 000000000..2c28401ec
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/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 */
diff --git a/test cases/frameworks/22 gir link order/meson.build b/test cases/frameworks/22 gir link order/meson.build
new file mode 100644
index 000000000..224eaf6fb
--- /dev/null
+++ b/test cases/frameworks/22 gir link order/meson.build
@@ -0,0 +1,41 @@
+project('gir link order', 'c')
+
+if not dependency('glib-2.0', required : false).found()
+  error('MESON_SKIP_TEST glib not found.')
+endif
+
+gnome = import('gnome')
+glib = dependency('glib-2.0')
+gobject = dependency('gobject-2.0')
+
+# get-prgname is a shared library which uses a function from glib-2.0. It is
+# used to introduce external -L flags which may cause -L order problems.
+subdir('get-prgname')
+
+# fake-gthread is a shared library which has the same name as gthread-2.0 from
+# GLib. This is used to simulate the case where an older or unrelated version
+# of a library is already installed on the system. Our meson sample library
+# defined below uses a function from fake-gthread. If meson messes up -L order,
+# the linker will find libgthread-2.0.so installed on the system and fail to
+# find the symbol our meson sample library uses.
+subdir('fake-gthread')
+
+meson_sample_sources = ['meson-sample.c', 'meson-sample.h']
+meson_sample_lib = shared_library(
+  'sample',
+  sources : meson_sample_sources,
+  dependencies : [gobject, get_prgname, fake_gthread],
+  install : false,
+)
+
+gnome.generate_gir(
+  meson_sample_lib,
+  sources : meson_sample_sources,
+  nsversion : '1.0',
+  namespace : 'Meson',
+  symbol_prefix : 'meson',
+  identifier_prefix : 'Meson',
+  includes : ['GObject-2.0'],
+  install : false,
+  build_by_default: true,
+)