The function 'org-in-src-block-p' always returns nil on my system
running Windows 10.

How to reproduce this bug starting from 'emacs -Q':
Define a function 'test-org-in-src-block-p' in the scratch buffer as
follows:

(defun test-org-in-src-block-p ()
  (interactive)
  (print (org-in-src-block-p)))

Navigate to a src block in org mode and call 'M-x
test-org-in-src-block-p'. Now nil is printed to the message buffer.

I should mention that on my other system running a Linux distribution I
do not have this problem. I know that this bug was also reported by Ryan
on 07 Aug 2014, as his bug report is still in the org mailing list
archives. Ryan's bug report can be found here:

https://lists.gnu.org/archive/html/emacs-orgmode/2014-08/msg00305.html






In GNU Emacs 25.3.1 (x86_64-w64-mingw32)
 of 2017-09-12 built on KAEL
Windowing system distributor 'Microsoft Corp.', version 10.0.17134
Configured using:
 'configure --prefix=/tmp/emacs --without-imagemagick --without-dbus
 --with-modules 'CFLAGS=-O2 -g0''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS MODULES

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1252

Major mode: Org

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-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
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Undo! [10 times]
user-error: No further undo information [3 times]

nil

You can run the command ‘test-in-block’ with M-x t-bl RET

nil

Making completion list...

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec
password-cache epg epg-config mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util help-fns help-mode mail-prsvr mail-utils org-element
org-rmail org-mhe org-irc org-info org-gnus gnus-util org-docview
doc-view subr-x jka-compr image-mode dired cl-loaddefs pcase cl-lib
org-bibtex bibtex org-bbdb org-w3m org org-macro org-footnote
org-pcomplete pcomplete org-list org-faces org-entities noutline outline
easy-mmode org-version ob-emacs-lisp ob ob-tangle ob-ref ob-lob ob-table
ob-exp org-src ob-keys ob-comint comint ansi-color ring ob-core ob-eval
org-compat org-macs org-loaddefs format-spec find-func cal-menu easymenu
calendar cal-loaddefs time-date mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp
disp-table w32-win w32-vars term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cl-generic cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote w32notify w32 multi-tty
make-network-process emacs)

Memory information:
((conses 16 142694 8689)
 (symbols 56 26277 0)
 (miscs 48 67 99)
 (strings 32 37651 5222)
 (string-bytes 1 1140795)
 (vectors 16 19091)
 (vector-slots 8 497556 4809)
 (floats 8 209 56)
 (intervals 56 350 31)
 (buffers 976 19))