Add test to ensure that fwd decls are sorted

devtools/checks/check-scg-cpp-style.py

@@ -98,6 +98,14 @@ def check_block(fn, t, name, errs):
     elif m.group(5) != '\n':
         errs.append(f"more than one blank line below {name} block in file {fn}")
 
+def check_fwd_decl_sorted(fn, t, errs):
+    for m in re.finditer(r'((class|struct) (\w+);([ ]*//.*)?\n)+', t):
+        decls_txt = m.group(0)
+        decls_arr = decls_txt.rstrip('\n').split('\n')
+        if decls_arr != sorted(decls_arr):
+            errs.append(f"forward declarations not sorted in file {fn}")
+            return
+
 ####################################################################################################
 # main
 ####################################################################################################
@@ -114,11 +122,14 @@ if __name__ == "__main__":
 
     # tests on each file:
     for fn in allfiles:
+        stem, suffix = split_fname(fn)
         with open(fn, 'r') as fd:
             t = fd.read()
         check_block(fn, t, 'include', errs)
         check_block(fn, t, 'using', errs)
-        check_block(fn, t, 'fwd decl', errs)
+        if suffix == 'h':
+            check_block(fn, t, 'fwd decl', errs)
+            check_fwd_decl_sorted(fn, t, errs)
 
     # tests on file pairs:
     for fn in allfiles: