Add untested code for searching for C and C++ headers in basic projects

autoload/ale/handlers/c.vim

@@ -0,0 +1,59 @@
+" Author: w0rp <devw0rp@gmail.com>
+" Desciption: Functions for integrating with C and C++ compilers.
+
+function! ale#handlers#c#FindProjectRoot(buffer) abort
+    for l:project_filename in ['Makefile', 'CMakeLists.txt']
+        let l:full_path = ale#path#FindNearestFile(a:buffer, l:project_filename)
+
+        if !empty(l:full_path)
+            return fnamemodify(l:full_path, ':h')
+        endif
+    endfor
+
+    return ''
+endfunction
+
+" Given a buffer number, search for a project root, and output a List
+" of directories to include based on some heuristics.
+"
+" For projects with headers in the project root, the project root will
+" be returned.
+"
+" For projects with an 'include' directory, that directory will be returned.
+function! ale#handlers#c#FindLocalHeaderPaths(buffer) abort
+    let l:project_root = ale#handlers#c#FindProjectRoot(a:buffer)
+
+    if empty(l:project_root)
+        return []
+    endif
+
+    " See if we can find .h files directory in the project root.
+    " If we can, that's our include directory.
+    if !empty(globpath(l:project_root, '*.h', 0))
+        return [l:project_root]
+    endif
+
+    " Look for .hpp files too.
+    if !empty(globpath(l:project_root, '*.hpp', 0))
+        return [l:project_root]
+    endif
+
+    " If we find an 'include' directory in the project root, then use that.
+    if isdirectory(l:project_root . '/include')
+        return [simplify(l:project_root . '/include')]
+    endif
+
+    return []
+endfunction
+
+" Given a List of include paths, create a string containing the -I include
+" options for those paths, with the paths escaped for use in the shell.
+function! ale#handlers#c#IncludeOptions(include_paths) abort
+    let l:option_list = []
+
+    for l:path in a:include_paths
+        call add(l:option_list, '-I' . ale#Escape(l:path))
+    endfor
+
+    return join(l:option_list)
+endfunction