C: option to remove errors from included files (#70)

syntax_checkers/c.vim

@@ -40,11 +40,17 @@
 " g:syntastic_c_include_dirs. This list can be used like this:
 "
 "   let g:syntastic_c_include_dirs = [ 'includes', 'headers' ]
-
+"
 " Moreover it is possible to add additional compiler options to the syntax
 " checking execution via the variable 'g:syntastic_c_compiler_options':
 "
 "   let g:syntastic_c_compiler_options = ' -ansi'
+"
+" Using the global variable 'g:syntastic_c_remove_include_errors' you can
+" specify whether errors of files included via the g:syntastic_c_include_dirs'
+" setting are removed from the result set:
+"
+"   let g:syntastic_c_remove_include_errors = 1
 
 if exists('loaded_c_syntax_checker')
     finish
@@ -107,13 +113,17 @@ function! SyntaxCheckers_c_GetLocList()
         let makeprg .= g:syntastic_c_compiler_options
     endif
 
+    " check if the user manually set some cflags
     if !exists('b:syntastic_c_cflags')
+        " check whether to search for include files at all
         if !exists('g:syntastic_c_no_include_search') ||
                     \ g:syntastic_c_no_include_search != 1
+            " refresh the include file search if desired
             if exists('g:syntastic_c_auto_refresh_includes') &&
                         \ g:syntastic_c_auto_refresh_includes != 0
                 let makeprg .= syntastic#c#SearchHeaders()
             else
+                " search for header includes if not cached already
                 if !exists('b:syntastic_c_includes')
                     let b:syntastic_c_includes = syntastic#c#SearchHeaders()
                 endif
@@ -121,10 +131,22 @@ function! SyntaxCheckers_c_GetLocList()
             endif
         endif
     else
+        " use the user-defined cflags
         let makeprg .= b:syntastic_c_cflags
     endif
 
-    return SyntasticMake({ 'makeprg': makeprg, 'errorformat': errorformat })
+    " process makeprg
+    let errors = SyntasticMake({ 'makeprg': makeprg,
+                \ 'errorformat': errorformat })
+
+    " filter the processed errors if desired
+    if exists('g:syntastic_c_remove_include_errors') &&
+                \ g:syntastic_c_remove_include_errors != 0
+        return filter(errors,
+                    \ 'has_key(v:val, "bufnr") && v:val["bufnr"]=='.bufnr(''))
+    else
+        return errors
+    endif
 endfunction
 
 let &cpo = s:save_cpo