read builtin disregards IFS when interrupted by trapped signal

[Andriy Martynets]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
-DSHELL -DHAVE_CONFIG_H   -I.  -I../. -I.././include -I.././lib 
-D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat 
-Werror=format-security -Wall
uname output: Linux admin-laptop-debian 4.4.0 #4 SMP Sat May 14 22:23:09 
EEST 2016 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.3
Patch Level: 42
Release Status: release

Description:
The read builtin disregards (or sporadically uses unpredictable value of)
the IFS variable when is interrupted by a trapped signal.

Repeat-By:
- install a trap for a signal, say SIGALRM or SIGUSR1
- cycle read from a process with a custom IFS to split read string into 
variables
- each interrupted read will return the string splitted in wrong way

Attached script demonstrates the bug.

Thank you in advance.

With best regards,
Andriy Martynets

read-test
Description: Text document