From 1bec8463dd4c5f62cc12c194f03956162ce9356b Mon Sep 17 00:00:00 2001
From: Alex Reinking <alex.reinking@gmail.com>
Date: Tue, 14 Feb 2023 15:45:49 -0800
Subject: [PATCH] Add depfile support to CMake rules (#329)

---
 src/exo/cmake/AddExoLibrary.cmake |  6 ++++--
 src/exo/main.py                   | 22 +++++++++++++++++++++-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/exo/cmake/AddExoLibrary.cmake b/src/exo/cmake/AddExoLibrary.cmake
index cbf7f549c..9829daee6 100644
--- a/src/exo/cmake/AddExoLibrary.cmake
+++ b/src/exo/cmake/AddExoLibrary.cmake
@@ -10,7 +10,7 @@ function(add_exo_library)
     list(APPEND source_files "${src}")
   endforeach ()
 
-  set(intdir "${CMAKE_CURRENT_BINARY_DIR}/${ARG_NAME}.exo")
+  set(intdir "${ARG_NAME}.exo")
   set(files "${intdir}/${ARG_NAME}.c" "${intdir}/${ARG_NAME}.h")
 
   list(TRANSFORM ARG_PYTHONPATH PREPEND "--modify;PYTHONPATH=path_list_append:")
@@ -21,10 +21,12 @@ function(add_exo_library)
             $<TARGET_FILE:Exo::compiler> -o "${intdir}" --stem "${ARG_NAME}"
             ${source_files}
     DEPENDS ${source_files}
+    DEPFILE "${intdir}/${ARG_NAME}.d"
     VERBATIM
   )
 
+  list(TRANSFORM files PREPEND "${CMAKE_CURRENT_BINARY_DIR}/")
   add_library(${ARG_NAME} ${files})
   add_library(${PROJECT_NAME}::${ARG_NAME} ALIAS ${ARG_NAME})
-  target_include_directories(${ARG_NAME} PUBLIC "$<BUILD_INTERFACE:${intdir}>")
+  target_include_directories(${ARG_NAME} PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/${intdir}>")
 endfunction()
diff --git a/src/exo/main.py b/src/exo/main.py
index 583045a10..4e50b1432 100644
--- a/src/exo/main.py
+++ b/src/exo/main.py
@@ -2,6 +2,7 @@
 import importlib
 import importlib.machinery
 import importlib.util
+import inspect
 import sys
 from pathlib import Path
 
@@ -32,7 +33,6 @@ def main():
 
     outdir = Path(args.outdir)
     outdir.mkdir(parents=True, exist_ok=True)
-    outdir = outdir.resolve(strict=True)
 
     library = [
         proc
@@ -41,6 +41,26 @@ def main():
     ]
 
     exo.compile_procs(library, outdir, f"{args.stem}.c", f"{args.stem}.h")
+    write_depfile(outdir, args.stem)
+
+
+def write_depfile(outdir, stem):
+    modules = set()
+    for mod in sys.modules.values():
+        try:
+            modules.add(inspect.getfile(mod))
+        except TypeError:
+            pass  # this is the case for built-in modules
+
+    c_file = outdir / f"{stem}.c"
+    h_file = outdir / f"{stem}.h"
+    depfile = outdir / f"{stem}.d"
+
+    sep = " \\\n  "
+    deps = sep.join(sorted(modules))
+    contents = f"{c_file} {h_file} : {deps}"
+
+    depfile.write_text(contents)
 
 
 def get_procs_from_module(user_module):