[pushed] Fix regression from gdbarch registry change

[pushed] Fix regression from gdbarch registry change

[Tom Tromey via Gdb-patches]

The gdbarch registry patch introduced a regression that could cause a
crash when opening files in gdb.  The bug is that, previously, the
solib ops would default to current_target_so_ops; but the patch
changed this code to default to nullptr.  This patch fixes the bug by
reintroducing the earlier behavior.  This is PR gdb/29449.

I managed to reproduce the bug with a riscv-elf build and then
verified that this fixes the problem.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29449
---
 gdb/solib.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/solib.c b/gdb/solib.c
index d889673dabf..25adf586a02 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -64,7 +64,13 @@ static const registry<gdbarch>::key<const struct target_so_ops,
 static const struct target_so_ops *
 solib_ops (struct gdbarch *gdbarch)
 {
-  return solib_data.get (gdbarch);
+  const struct target_so_ops *result = solib_data.get (gdbarch);
+  if (result == nullptr)
+    {
+      result = current_target_so_ops;
+      set_solib_ops (gdbarch, current_target_so_ops);
+    }
+  return result;
 }
 
 /* Set the solib operations for GDBARCH to NEW_OPS.  */
-- 
2.34.1