[Ada] Fix oversight in GNAT.Sockets.Thin

[Eric Botcazou]

As reported in the PR, both C_Accept and C_Socket call Disable_SIGPIPE 
unconditionally, in other words even though the descriptor is invalid.

Tested on x86-64/Linux, applied on the mainline and 16 branch.


2026-10-07  Hodong Kim  <hod...@nimfsoft.com>

        PR ada/127759
        * libgnat/g-socthi.adb (C_Accept): Do not call Disable_SIGPIPE
        on failure.
        (C_Socket): Likewise.

-- 
Eric Botcazou
diff --git a/gcc/ada/libgnat/g-socthi.adb b/gcc/ada/libgnat/g-socthi.adb
index f7fa4007dd1..a369c98a9e2 100644
--- a/gcc/ada/libgnat/g-socthi.adb
+++ b/gcc/ada/libgnat/g-socthi.adb
@@ -187,7 +187,10 @@ package body GNAT.Sockets.Thin is
          Discard := C_Ioctl (R, SOSC.FIONBIO, Val'Access);
       end if;
 
-      Disable_SIGPIPE (R);
+      if R /= Failure then
+         Disable_SIGPIPE (R);
+      end if;
+
       return R;
    end C_Accept;
 
@@ -533,7 +536,11 @@ package body GNAT.Sockets.Thin is
          Discard := C_Ioctl (R, SOSC.FIONBIO, Val'Access);
          Set_Non_Blocking_Socket (R, False);
       end if;
-      Disable_SIGPIPE (R);
+
+      if R /= Failure then
+         Disable_SIGPIPE (R);
+      end if;
+
       return R;
    end C_Socket;