[Pkg-libvirt-commits] [libguestfs] 03/65: lib: Fix static linking by forcing launch-*.o objects to be always linked.

[Hilko Bengen]

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bengen pushed a commit to branch experimental
in repository libguestfs.

commit f1007fc26d58a62b3692f64a6d8219ad9221510f
Author: Richard W.M. Jones <rjones at redhat.com>
Date:   Sat Mar 28 10:15:57 2015 +0000

    lib: Fix static linking by forcing launch-*.o objects to be always linked.
    
    Because the launch-*.o objects only contain statically scoped
    declarations, the linker doesn't need to link them in.  This causes a
    problem when static linking as they will be left out of the final
    binary, and so no backends will be available.
    
    This is essentially the same problem as described here:
    
    https://stackoverflow.com/questions/1202494/why-doesnt-attribute-constructor-work-in-a-static-library
---
 src/guestfs-internal.h |  8 ++++++++
 src/launch-direct.c    |  5 ++---
 src/launch-libvirt.c   |  5 ++---
 src/launch-uml.c       |  5 ++---
 src/launch-unix.c      |  5 ++---
 src/launch.c           | 13 +++++++++++++
 6 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/src/guestfs-internal.h b/src/guestfs-internal.h
index 43cdd4d..414a634 100644
--- a/src/guestfs-internal.h
+++ b/src/guestfs-internal.h
@@ -883,6 +883,14 @@ extern void guestfs_int_cleanup_cmd_close (struct command **);
 extern char *guestfs_int_drive_source_qemu_param (guestfs_h *g, const struct drive_source *src);
 extern bool guestfs_int_discard_possible (guestfs_h *g, struct drive *drv, unsigned long qemu_version);
 
+/* launch-*.c constructors */
+void guestfs_int_init_direct_backend (void) __attribute__((constructor));
+#ifdef HAVE_LIBVIRT
+void guestfs_int_init_libvirt_backend (void) __attribute__((constructor));
+#endif
+void guestfs_int_init_uml_backend (void) __attribute__((constructor));
+void guestfs_int_init_unix_backend (void) __attribute__((constructor));
+
 /* guid.c */
 extern int guestfs_int_validate_guid (const char *);
 
diff --git a/src/launch-direct.c b/src/launch-direct.c
index 5753236..ea67ec9 100644
--- a/src/launch-direct.c
+++ b/src/launch-direct.c
@@ -1544,9 +1544,8 @@ static struct backend_ops backend_direct_ops = {
   .max_disks = max_disks_direct,
 };
 
-static void init_backend (void) __attribute__((constructor));
-static void
-init_backend (void)
+void
+guestfs_int_init_direct_backend (void)
 {
   guestfs_int_register_backend ("direct", &backend_direct_ops);
 }
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index 45d0d76..f46782c 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -2262,9 +2262,8 @@ static struct backend_ops backend_libvirt_ops = {
   .hot_remove_drive = hot_remove_drive_libvirt,
 };
 
-static void init_backend (void) __attribute__((constructor));
-static void
-init_backend (void)
+void
+guestfs_int_init_libvirt_backend (void)
 {
   guestfs_int_register_backend ("libvirt", &backend_libvirt_ops);
 }
diff --git a/src/launch-uml.c b/src/launch-uml.c
index 34e7068..785548c 100644
--- a/src/launch-uml.c
+++ b/src/launch-uml.c
@@ -609,9 +609,8 @@ static struct backend_ops backend_uml_ops = {
   .max_disks = max_disks_uml,
 };
 
-static void init_backend (void) __attribute__((constructor));
-static void
-init_backend (void)
+void
+guestfs_int_init_uml_backend (void)
 {
   guestfs_int_register_backend ("uml", &backend_uml_ops);
 }
diff --git a/src/launch-unix.c b/src/launch-unix.c
index 99a6e80..dae4389 100644
--- a/src/launch-unix.c
+++ b/src/launch-unix.c
@@ -120,9 +120,8 @@ static struct backend_ops backend_unix_ops = {
   .shutdown = shutdown_unix,
 };
 
-static void init_backend (void) __attribute__((constructor));
-static void
-init_backend (void)
+void
+guestfs_int_init_unix_backend (void)
 {
   guestfs_int_register_backend ("unix", &backend_unix_ops);
 }
diff --git a/src/launch.c b/src/launch.c
index cbaef28..fbe9246 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -527,3 +527,16 @@ guestfs_int_set_backend (guestfs_h *g, const char *method)
 
   return 0;
 }
+
+/* This hack is only required to make static linking work.  See:
+ * https://stackoverflow.com/questions/1202494/why-doesnt-attribute-constructor-work-in-a-static-library
+ */
+void *
+guestfs_int_force_load_backends[] = {
+  guestfs_int_init_direct_backend,
+#ifdef HAVE_LIBVIRT
+  guestfs_int_init_libvirt_backend,
+#endif
+  guestfs_int_init_uml_backend,
+  guestfs_int_init_unix_backend,
+};

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