[binutils-gdb] Fix regression from gdbarch registry change

[Tom Tromey <tromey@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ce81f9d6fa885a3faa41613debc8771304dc469b

commit ce81f9d6fa885a3faa41613debc8771304dc469b
Author: Tom Tromey <tromey@adacore.com>
Date:   Mon Aug 8 09:56:47 2022 -0600

    Fix regression from gdbarch registry change
    
    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

Diff:
---
 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.  */