bug#21275: 24.5; Selection deleted with electric pair mode in cc mode

[nljlistbox2@gmail.com (N. Jackson)]

In cc mode, with delete selection mode and electric pair mode both on,
entering a "(" when there is an active selection erroneously deletes the
selection (and inserts "()" in the buffer) rather than inserting a "("
before the selection and a ")" after it. This is inconsistent with the
seemingly correct [1] and useful behaviour in (for example) text mode,
fundamental mode, and lisp mode.

The bug affects both code and in comments.

STEPS TO REPRODUCE:

$ cat > test.c
/* This is a short comment. */
int test(void){
  return 0;
}
^D
$ emacs -Q
M-x delete-selection-mode
M-x electric-pair-mode
C-x f test.c RET
;; Select the word "short" in the first line.
(
;; Now select the "0" in the return statement.
(

EXPECTED RESULT:

/* This is a (short) comment. */
int test(void){
  return (0);
}

OBSERVED RESULT:

/* This is a () comment. */
int test(void){
  return ();
}

[1] http://debbugs.gnu.org/cgi/bugreport.cgi?bug=11520


In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.14.14)
 of 2015-07-25 on moondust
Windowing system distributor `Fedora Project', version 11.0.11603000
System Description:	Fedora release 21 (Twenty One)

Configured using:
 `configure --prefix=/home/nlj/local/ --enable-checking=yes,glyphs
 'CFLAGS=-O0 -g3 -ggdb''

Important settings:
  value of $LC_MONETARY: en_DK.utf8
  value of $LC_NUMERIC: en_DK.utf8
  value of $LC_TIME: en_DK.utf8
  value of $LANG: en_CA.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: C/l

Minor modes in effect:
  flyspell-mode: t
  recentf-mode: t
  delete-selection-mode: t
  show-paren-mode: t
  savehist-mode: t
  electric-pair-mode: t
  display-time-mode: t
  display-battery-mode: t
  desktop-save-mode: t
  cua-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  global-visual-line-mode: t
  visual-line-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent messages:
Auto-saving...done
Making completion list...
Type C-x 1 to delete the help window.
Undo! [2 times]
Auto-saving...
Updating buffer list...done
Commands: m, u, t, RET, g, k, S, D, Q; q to quit; h for help
Mark set
Mark saved where search started
Mark set
call-interactively: End of buffer

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