Account for trailing bytes read from bfd_bread

[Alan Modra]

Noticed when debugging the >2G obstack corruption of gdb data.  When
we have a truncated read, we ought to return the amount read.  Not
that it matters very much on an error return..

    	* cache.c (cache_bread_1): Don't return -1 when fread returns
    	a positive value.

diff --git a/bfd/cache.c b/bfd/cache.c
index 27fe70a..ffda004 100644
--- a/bfd/cache.c
+++ b/bfd/cache.c
@@ -310,7 +310,7 @@ cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
   if (nread == (file_ptr)-1)
     {
       bfd_set_error (bfd_error_system_call);
-      return -1;
+      return nread;
     }
 #else
   nread = fread (buf, 1, nbytes, f);
@@ -320,7 +320,7 @@ cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
   if (nread < nbytes && ferror (f))
     {
       bfd_set_error (bfd_error_system_call);
-      return -1;
+      return nread;
     }
 #endif
   if (nread < nbytes)

-- 
Alan Modra
Australia Development Lab, IBM