Hotfix broken 24.3 compatibility with subr-x

Resolves #375

core/emacs-backports.el

@@ -0,0 +1,27 @@
+(unless (featurep 'subr-x)
+    ;; `subr-x' function for Emacs 24.3 and below
+    (defsubst string-join (strings &optional separator)
+      "Join all STRINGS using SEPARATOR."
+      (mapconcat 'identity strings separator))
+
+    (defsubst string-trim-left (string)
+      "Remove leading whitespace from STRING."
+      (if (string-match "\\`[ \t\n\r]+" string)
+          (replace-match "" t t string)
+        string))
+
+    (defsubst string-trim-right (string)
+      "Remove trailing whitespace from STRING."
+      (if (string-match "[ \t\n\r]+\\'" string)
+          (replace-match "" t t string)
+        string))
+
+    (defsubst string-trim (string)
+      "Remove leading and trailing whitespace from STRING."
+      (string-trim-left (string-trim-right string)))
+
+    (defsubst string-empty-p (string)
+      "Check whether STRING is empty."
+      (string= string "")))
+
+(provide 'emacs-backports)

core/spacemacs-mode.el

@@ -1,7 +1,8 @@
 (setq message-log-max 16384)
 (defconst emacs-start-time (current-time))
 
-(require 'subr-x)
+(require 'subr-x nil 'noerror)
+(require 'emacs-backports)
 
 (defconst spacemacs-version "0.41.0"
   "Spacemacs version.")
@@ -9,11 +10,6 @@
 (defconst spacemacs-min-version "24.3"
   "Mininal required version of Emacs.")
 
-(defconst spacemacs-core-directory
-  (expand-file-name (concat user-emacs-directory "core/"))
-  "Spacemacs core directory.")
-(add-to-list 'load-path spacemacs-core-directory)
-
 (defconst spacemacs-banner-directory
   (expand-file-name (concat spacemacs-core-directory "banners/"))
   "Spacemacs banners directory.")
@@ -299,3 +295,5 @@ of size LOADING-DOTS-CHUNK-THRESHOLD."
   (insert-button "Update Spacemacs" 'action (lambda (b) (configuration-layer/update-packages)) 'follow-link t)
   (insert "\n\n")
   )
+
+(provide 'spacemacs-mode)

init.el

@@ -1,4 +1,9 @@
-(load (concat user-emacs-directory "core/spacemacs-mode.el"))
+(defconst spacemacs-core-directory
+  (expand-file-name (concat user-emacs-directory "core/"))
+  "Spacemacs core directory.")
+(add-to-list 'load-path spacemacs-core-directory)
+
+(require 'spacemacs-mode)
 (require 'configuration-layer)
 
 (when (spacemacs/emacs-version-ok)