njlr

int add(int x, int y);

njlr

for each header file:
  hash the file
  generate an include guard from the hash
  wrap the contents 
  output into a new header file

njlr

#pragma once

struct foo {
  int member;
};

njlr

struct foo {
  int member;
};

njlr

#ifndef HEADER_HAS_BEEN_INCLUDED
#define HEADER_HAS_BEEN_INCLUDED

struct foo {
  int member;
};

#endif
#ifndef HEADER_HAS_BEEN_INCLUDED
#define HEADER_HAS_BEEN_INCLUDED

njlr

#include "foo.hpp"
#include "foo.hpp"

njlr

#ifndef HEADER_HAS_BEEN_INCLUDED
#define HEADER_HAS_BEEN_INCLUDED

struct foo {
  int member;
};

#endif

njlr

$ buck build :mathutils

$ ls ./buck-out/gen/mathutils#header-mode-symlink-tree-with-header-map\,headers/mathutils/
add.hpp mathutils.hpp sub.hpp

njlr

cxx_library(
  name = 'mathutils',
  header_namespace = 'mathutils',
  exported_headers = merge_dicts(subdir_glob([
    ('mathutils/include', '**/*.hpp'),
  ]), {
    'mathutils.hpp': ':single-header', 
  }),
  srcs = glob([
    'mathutils/src/**/*.cpp',

njlr

def merge_dicts(x, y):
  z = x.copy()
  z.update(y)
  return z