Re: [PATCHv3 8/8] gdb/gdbserver: share x86/linux tdesc caching

[Andrew Burgess <aburgess@redhat.com>]

Simon pointed out some build issues encountered when building with
Clang.  While test building using Clang an additional issue was
highlighted, which I've fixed by pushing the patch below.

Sorry for anyone who ran into this issue.

Thanks,
Andrew

---

commit 24df37a10f8773ad5db07dc000f694d6405e3a36
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Tue Mar 26 12:05:07 2024 +0000

    gdb: fix possible uninitialised variable use
    
    After this commit:
    
      commit 198ff6ff819c240545f9fc68b39636fd376d4ba9
      Date:   Tue Jan 30 15:37:23 2024 +0000
    
          gdb/gdbserver: share x86/linux tdesc caching
    
    a possible use of an uninitialised variable was introduced, the
    'tdesc' variable in i386_linux_core_read_description might be read
    without being written too if 'xcr0' was 0.
    
    This is fixed in this commit.  I've updated the function to follow the
    same pattern as amd64_linux_core_read_description, if xcr0 is 0 then
    we select a default xcr0 value and use that to select a tdesc.

diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index ed1442236e8..2e84384306d 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -700,17 +700,15 @@ i386_linux_core_read_description (struct gdbarch *gdbarch,
   x86_xsave_layout layout;
   uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, layout);
 
-  const struct target_desc *tdesc;
-  if (xcr0 != 0)
-    tdesc = i386_linux_read_description (xcr0);
-
-  if (tdesc != NULL)
-    return tdesc;
+  if (xcr0 == 0)
+    {
+      if (bfd_get_section_by_name (abfd, ".reg-xfp") != nullptr)
+	xcr0 = X86_XSTATE_SSE_MASK;
+      else
+	xcr0 = X86_XSTATE_X87_MASK;
+    }
 
-  if (bfd_get_section_by_name (abfd, ".reg-xfp") != NULL)
-    return i386_linux_read_description (X86_XSTATE_SSE_MASK);
-  else
-    return i386_linux_read_description (X86_XSTATE_X87_MASK);
+  return i386_linux_read_description (xcr0);
 }
 
 /* Similar to i386_supply_fpregset, but use XSAVE extended state.  */