diff --git a/autoload/syntastic/c.vim b/autoload/syntastic/c.vim
index 9c2ad169..993982e6 100644
--- a/autoload/syntastic/c.vim
+++ b/autoload/syntastic/c.vim
@@ -15,41 +15,28 @@ function! syntastic#c#NullOutput()
     return known_os ? '-o ' . syntastic#util#DevNull() : ''
 endfunction
 
-" get the gcc include directory argument depending on the default
-" includes and the optional user-defined 'g:syntastic_c_include_dirs'
-function! syntastic#c#GetIncludeDirs(filetype)
-    let include_dirs = []
-
-    if !exists('g:syntastic_'.a:filetype.'_no_default_include_dirs') ||
-        \ !g:syntastic_{a:filetype}_no_default_include_dirs
-        let include_dirs = copy(s:default_includes)
-    endif
-
-    if exists('g:syntastic_'.a:filetype.'_include_dirs')
-        call extend(include_dirs, g:syntastic_{a:filetype}_include_dirs)
-    endif
-
-    return join(map(syntastic#util#unique(include_dirs), '"-I" . v:val'), ' ')
-endfunction
-
 " read additional compiler flags from the given configuration file
 " the file format and its parsing mechanism is inspired by clang_complete
 function! syntastic#c#ReadConfig(file)
     " search in the current file's directory upwards
     let config = findfile(a:file, '.;')
-    if config == '' || !filereadable(config) | return '' | endif
+    if config == '' || !filereadable(config)
+        return ''
+    endif
 
     " convert filename into absolute path
-    let filepath = substitute(fnamemodify(config, ':p:h'), '\', '/', 'g')
+    let filepath = fnamemodify(config, ':p:h')
 
     " try to read config file
     try
-        let lines = map(readfile(config),
-                    \ 'substitute(v:val, ''\'', ''/'', ''g'')')
-    catch /E484/
+        let lines = readfile(config)
+    catch /^Vim\%((\a\+)\)\=:E484/
         return ''
     endtry
 
+    " filter out empty lines and comments
+    call filter(lines, 'v:val !~ ''\v^(\s*#|$)''')
+
     let parameters = []
     for line in lines
         let matches = matchlist(line, '\C^\s*-I\s*\(\S\+\)')
@@ -58,67 +45,14 @@ function! syntastic#c#ReadConfig(file)
             if match(matches[1], '^\%(/\|\a:\)') != -1
                 call add(parameters, '-I' . matches[1])
             else
-                call add(parameters, '-I' . filepath . '/' . matches[1])
+                call add(parameters, '-I' . filepath . syntastic#util#Slash() . matches[1])
             endif
         else
             call add(parameters, line)
         endif
     endfor
 
-    return join(parameters, ' ')
-endfunction
-
-" search the first 100 lines for include statements that are
-" given in the handlers dictionary
-function! syntastic#c#SearchHeaders()
-    let includes = ''
-    let files = []
-    let found = []
-    let lines = filter(getline(1, 100), 'v:val =~# "^\s*#\s*include"')
-
-    " search current buffer
-    for line in lines
-        let file = matchstr(line, '"\zs\S\+\ze"')
-        if file != ''
-            call add(files, file)
-            continue
-        endif
-        for handler in s:handlers
-            if line =~# handler["regex"]
-                let includes .= call(handler["func"], handler["args"])
-                call add(found, handler["regex"])
-                break
-            endif
-        endfor
-    endfor
-
-    " search included headers
-    for hfile in files
-        if hfile != ''
-            let filename = expand('%:p:h') . (has('win32') ?
-                        \ '\' : '/') . hfile
-            try
-                let lines = readfile(filename, '', 100)
-            catch /E484/
-                continue
-            endtry
-            let lines = filter(lines, 'v:val =~# "^\s*#\s*include"')
-            for handler in s:handlers
-                if index(found, handler["regex"]) != -1
-                    continue
-                endif
-                for line in lines
-                    if line =~# handler["regex"]
-                        let includes .= call(handler["func"], handler["args"])
-                        call add(found, handler["regex"])
-                        break
-                    endif
-                endfor
-            endfor
-        endif
-    endfor
-
-    return includes
+    return join(map(parameters, 'shellescape(fnameescape(v:val))'), ' ')
 endfunction
 
 " GetLocList() for C-like compilers
@@ -134,7 +68,7 @@ function! syntastic#c#GetLocList(filetype, options)
                 \ g:syntastic_{ft}_compiler .
                 \ ' ' . get(a:options, 'makeprg_headers', '') .
                 \ ' ' . g:syntastic_{ft}_compiler_options .
-                \ ' ' . syntastic#c#GetIncludeDirs(ft) .
+                \ ' ' . s:GetIncludeDirs(ft) .
                 \ ' ' . syntastic#c#NullOutput() .
                 \ ' -c ' . shellescape(expand('%'))
         else
@@ -145,7 +79,7 @@ function! syntastic#c#GetLocList(filetype, options)
             \ g:syntastic_{ft}_compiler .
             \ ' ' . get(a:options, 'makeprg_main', '') .
             \ ' ' . g:syntastic_{ft}_compiler_options .
-            \ ' ' . syntastic#c#GetIncludeDirs(ft) .
+            \ ' ' . s:GetIncludeDirs(ft) .
             \ ' ' . shellescape(expand('%'))
     endif
 
@@ -156,11 +90,11 @@ function! syntastic#c#GetLocList(filetype, options)
             if ft ==# 'c' || ft ==# 'cpp'
                 " refresh the include file search if desired
                 if exists('g:syntastic_' . ft . '_auto_refresh_includes') && g:syntastic_{ft}_auto_refresh_includes
-                    let makeprg .= ' ' . syntastic#c#SearchHeaders()
+                    let makeprg .= ' ' . s:SearchHeaders()
                 else
                     " search for header includes if not cached already
                     if !exists('b:syntastic_' . ft . '_includes')
-                        let b:syntastic_{ft}_includes = syntastic#c#SearchHeaders()
+                        let b:syntastic_{ft}_includes = s:SearchHeaders()
                     endif
                     let makeprg .= ' ' . b:syntastic_{ft}_includes
                 endif
@@ -192,31 +126,94 @@ function! s:Init()
     let s:handlers = []
     let s:cflags = {}
 
-    call s:RegHandler('gtk', 'syntastic#c#CheckPKG',
-                \ ['gtk', 'gtk+-2.0', 'gtk+', 'glib-2.0', 'glib'])
-    call s:RegHandler('glib', 'syntastic#c#CheckPKG',
-                \ ['glib', 'glib-2.0', 'glib'])
-    call s:RegHandler('glade', 'syntastic#c#CheckPKG',
-                \ ['glade', 'libglade-2.0', 'libglade'])
-    call s:RegHandler('libsoup', 'syntastic#c#CheckPKG',
-                \ ['libsoup', 'libsoup-2.4', 'libsoup-2.2'])
-    call s:RegHandler('webkit', 'syntastic#c#CheckPKG',
-                \ ['webkit', 'webkit-1.0'])
-    call s:RegHandler('cairo', 'syntastic#c#CheckPKG',
-                \ ['cairo', 'cairo'])
-    call s:RegHandler('pango', 'syntastic#c#CheckPKG',
-                \ ['pango', 'pango'])
-    call s:RegHandler('libxml', 'syntastic#c#CheckPKG',
-                \ ['libxml', 'libxml-2.0', 'libxml'])
-    call s:RegHandler('freetype', 'syntastic#c#CheckPKG',
-                \ ['freetype', 'freetype2', 'freetype'])
-    call s:RegHandler('SDL', 'syntastic#c#CheckPKG',
-                \ ['sdl', 'sdl'])
-    call s:RegHandler('opengl', 'syntastic#c#CheckPKG',
-                \ ['opengl', 'gl'])
-    call s:RegHandler('ruby', 'syntastic#c#CheckRuby', [])
+    call s:RegHandler('cairo',     'syntastic#c#CheckPKG', ['cairo', 'cairo'])
+    call s:RegHandler('freetype',  'syntastic#c#CheckPKG', ['freetype', 'freetype2', 'freetype'])
+    call s:RegHandler('glade',     'syntastic#c#CheckPKG', ['glade', 'libglade-2.0', 'libglade'])
+    call s:RegHandler('glib',      'syntastic#c#CheckPKG', ['glib', 'glib-2.0', 'glib'])
+    call s:RegHandler('gtk',       'syntastic#c#CheckPKG', ['gtk', 'gtk+-2.0', 'gtk+', 'glib-2.0', 'glib'])
+    call s:RegHandler('libsoup',   'syntastic#c#CheckPKG', ['libsoup', 'libsoup-2.4', 'libsoup-2.2'])
+    call s:RegHandler('libxml',    'syntastic#c#CheckPKG', ['libxml', 'libxml-2.0', 'libxml'])
+    call s:RegHandler('pango',     'syntastic#c#CheckPKG', ['pango', 'pango'])
+    call s:RegHandler('SDL',       'syntastic#c#CheckPKG', ['sdl', 'sdl'])
+    call s:RegHandler('opengl',    'syntastic#c#CheckPKG', ['opengl', 'gl'])
+    call s:RegHandler('webkit',    'syntastic#c#CheckPKG', ['webkit', 'webkit-1.0'])
+
+    call s:RegHandler('php\.h',    'syntastic#c#CheckPhp',    [])
     call s:RegHandler('Python\.h', 'syntastic#c#CheckPython', [])
-    call s:RegHandler('php\.h', 'syntastic#c#CheckPhp', [])
+    call s:RegHandler('ruby',      'syntastic#c#CheckRuby',   [])
+endfunction
+
+" get the gcc include directory argument depending on the default
+" includes and the optional user-defined 'g:syntastic_c_include_dirs'
+function! s:GetIncludeDirs(filetype)
+    let include_dirs = []
+
+    if !exists('g:syntastic_'.a:filetype.'_no_default_include_dirs') || !g:syntastic_{a:filetype}_no_default_include_dirs
+        let include_dirs = copy(s:default_includes)
+    endif
+
+    if exists('g:syntastic_'.a:filetype.'_include_dirs')
+        call extend(include_dirs, g:syntastic_{a:filetype}_include_dirs)
+    endif
+
+    return join(map(syntastic#util#unique(include_dirs), 'shellescape(fnameescape("-I" . v:val))'), ' ')
+endfunction
+
+" search the first 100 lines for include statements that are
+" given in the handlers dictionary
+function! s:SearchHeaders()
+    let includes = ''
+    let files = []
+    let found = []
+    let lines = filter(getline(1, 100), 'v:val =~# "^\s*#\s*include"')
+
+    " search current buffer
+    for line in lines
+        let file = matchstr(line, '"\zs\S\+\ze"')
+        if file != ''
+            call add(files, file)
+            continue
+        endif
+
+        for handler in s:handlers
+            if line =~# handler["regex"]
+                let includes .= call(handler["func"], handler["args"])
+                call add(found, handler["regex"])
+                break
+            endif
+        endfor
+    endfor
+
+    " search included headers
+    for hfile in files
+        if hfile != ''
+            let filename = expand('%:p:h') . syntastic#util#Slash() . hfile
+
+            try
+                let lines = readfile(filename, '', 100)
+            catch /^Vim\%((\a\+)\)\=:E484/
+                continue
+            endtry
+
+            let lines = filter(lines, 'v:val =~# "^\s*#\s*include"')
+
+            for handler in s:handlers
+                if index(found, handler["regex"]) != -1
+                    continue
+                endif
+
+                for line in lines
+                    if line =~# handler["regex"]
+                        let includes .= call(handler["func"], handler["args"])
+                        call add(found, handler["regex"])
+                        break
+                    endif
+                endfor
+            endfor
+        endif
+    endfor
+
+    return includes
 endfunction
 
 " try to find library with 'pkg-config'
@@ -225,14 +222,14 @@ endfunction
 function! syntastic#c#CheckPKG(name, ...)
     if executable('pkg-config')
         if !has_key(s:cflags, a:name)
-            for i in range(a:0)
-                let l:cflags = system('pkg-config --cflags '.a:000[i])
+            for pkg in a:000
+                let pkg_flags = system('pkg-config --cflags ' . pkg)
                 " since we cannot necessarily trust the pkg-config exit code
                 " we have to check for an error output as well
-                if v:shell_error == 0 && l:cflags !~? 'not found'
-                    let l:cflags = ' '.substitute(l:cflags, "\n", '', '')
-                    let s:cflags[a:name] = l:cflags
-                    return l:cflags
+                if v:shell_error == 0 && pkg_flags !~? 'not found'
+                    let pkg_flags = ' ' . substitute(pkg_flags, "\n", '', '')
+                    let s:cflags[a:name] = pkg_flags
+                    return pkg_flags
                 endif
             endfor
         else
@@ -245,11 +242,11 @@ endfunction
 " try to find PHP includes with 'php-config'
 function! syntastic#c#CheckPhp()
     if executable('php-config')
-        if !exists('s:php_flags')
-            let s:php_flags = system('php-config --includes')
-            let s:php_flags = ' ' . substitute(s:php_flags, "\n", '', '')
+        if !has_key(s:cflags, 'php')
+            let s:cflags['php'] = system('php-config --includes')
+            let s:cflags['php'] = ' ' . substitute(s:cflags['php'], "\n", '', '')
         endif
-        return s:php_flags
+        return s:cflags['php']
     endif
     return ''
 endfunction
@@ -257,13 +254,12 @@ endfunction
 " try to find the ruby headers with 'rbconfig'
 function! syntastic#c#CheckRuby()
     if executable('ruby')
-        if !exists('s:ruby_flags')
-            let s:ruby_flags = system('ruby -r rbconfig -e '
-                        \ . '''puts Config::CONFIG["archdir"]''')
-            let s:ruby_flags = substitute(s:ruby_flags, "\n", '', '')
-            let s:ruby_flags = ' -I' . s:ruby_flags
+        if !has_key(s:cflags, 'ruby')
+            let s:cflags['ruby'] = system('ruby -r rbconfig -e ''puts Config::CONFIG["archdir"]''')
+            let s:cflags['ruby'] = substitute(s:cflags['ruby'], "\n", '', '')
+            let s:cflags['ruby'] = ' -I' . s:cflags['ruby']
         endif
-        return s:ruby_flags
+        return s:cflags['ruby']
     endif
     return ''
 endfunction
@@ -271,13 +267,13 @@ endfunction
 " try to find the python headers with distutils
 function! syntastic#c#CheckPython()
     if executable('python')
-        if !exists('s:python_flags')
-            let s:python_flags = system('python -c ''from distutils import '
-                        \ . 'sysconfig; import sys; sys.stdout.write(sysconfig.get_python_inc())''')
-            let s:python_flags = substitute(s:python_flags, "\n", '', '')
-            let s:python_flags = ' -I' . s:python_flags
+        if !has_key(s:cflags, 'python')
+            let s:cflags['python'] = system('python -c ''from distutils import ' .
+                \ 'sysconfig; import sys; sys.stdout.write(sysconfig.get_python_inc())''')
+            let s:cflags['python'] = substitute(s:cflags['python'], "\n", '', '')
+            let s:cflags['python'] = ' -I' . s:cflags['python']
         endif
-        return s:python_flags
+        return s:cflags['python']
     endif
     return ''
 endfunction
@@ -294,8 +290,13 @@ endfunction
 " }}}1
 
 " default include directories
-let s:default_includes = [ '.', '..', 'include', 'includes',
-            \ '../include', '../includes' ]
+let s:default_includes = [
+    \ '.',
+    \ '..',
+    \ 'include',
+    \ 'includes',
+    \ '..' . syntastic#util#Slash() . 'include',
+    \ '..' . syntastic#util#Slash() . 'includes' ]
 
 call s:Init()
 
diff --git a/autoload/syntastic/util.vim b/autoload/syntastic/util.vim
index 4e777b3d..b6f58d83 100644
--- a/autoload/syntastic/util.vim
+++ b/autoload/syntastic/util.vim
@@ -19,6 +19,11 @@ function! syntastic#util#DevNull()
     return '/dev/null'
 endfunction
 
+" Get directory separator
+function! syntastic#util#Slash() abort
+    return !exists("+shellslash") || &shellslash ? '/' : '\'
+endfunction
+
 "search the first 5 lines of the file for a magic number and return a map
 "containing the args and the executable
 "