From https://ftp.gnu.org/gnu/bash/bash-4.4-patches/bash44-002

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

			     BASH PATCH REPORT
			     =================

Bash-Release:	4.4
Patch-ID:	bash44-002

Bug-Reported-by:	Eric Pruitt <eric.pruitt@gmail.com>
Bug-Reference-ID:	<20160916055120.GA28272@sinister.codevat.com>
Bug-Reference-URL:	http://lists.gnu.org/archive/html/bug-bash/2016-09/msg00015.html

Bug-Description:

Bash-4.4 warns when discarding NUL bytes in command substitution output
instead of silently dropping them.  This patch changes the warnings from
one per NUL byte encountered to one warning per command substitution.

Patch (apply with `patch -p0'):

*** a/bash-4.4/subst.c	2016-08-30 16:46:38.000000000 -0400
--- b/subst.c	2016-09-26 10:20:19.000000000 -0400
***************
*** 5932,5935 ****
--- 5933,5937 ----
    int istring_index, istring_size, c, tflag, skip_ctlesc, skip_ctlnul;
    ssize_t bufn;
+   int nullbyte;
  
    istring = (char *)NULL;
***************
*** 5939,5942 ****
--- 5941,5946 ----
      skip_ctlesc |= *s == CTLESC, skip_ctlnul |= *s == CTLNUL;
  
+   nullbyte = 0;
+ 
    /* Read the output of the command through the pipe.  This may need to be
       changed to understand multibyte characters in the future. */
***************
*** 5957,5961 ****
  	{
  #if 1
! 	  internal_warning ("%s", _("command substitution: ignored null byte in input"));
  #endif
  	  continue;
--- 5961,5969 ----
  	{
  #if 1
! 	  if (nullbyte == 0)
! 	    {
! 	      internal_warning ("%s", _("command substitution: ignored null byte in input"));
! 	      nullbyte = 1;
! 	    }
  #endif
  	  continue;
*** a/bash-4.4/patchlevel.h	2016-06-22 14:51:03.000000000 -0400
--- b/patchlevel.h	2016-10-01 11:01:28.000000000 -0400
***************
*** 26,30 ****
     looks for to find the patch level (for the sccs version string). */
  
! #define PATCHLEVEL 1
  
  #endif /* _PATCHLEVEL_H_ */
--- 26,30 ----
     looks for to find the patch level (for the sccs version string). */
  
! #define PATCHLEVEL 2
  
  #endif /* _PATCHLEVEL_H_ */