py/makeqstrdefs.py: Propagate out errors from parallel pp step.

dpgeorge · dpgeorge · commit b9cceaa6fd61 · 2026-07-22T20:06:38.000+10:00
Commit e6380fa changed the pp step from `subprocess.check_output()` to use `subprocess.Popen()`, but did not check the return code of the process. That means any process errors (eg compiler error) are swallowed and do not stop the build. This commit fixes that by explicitly checking `proc.returncode` once the process is complete, and raising an exception. Signed-off-by: Damien George <damien@micropython.org>
diff --git a/py/makeqstrdefs.py b/py/makeqstrdefs.py
@@ -68,7 +68,8 @@ def pp(flags):
         def run(files):
             try:
                 filtered_lines = []
-                with subprocess.Popen(args.pp + flags + files, stdout=subprocess.PIPE) as proc:
+                cmd = args.pp + flags + files
+                with subprocess.Popen(cmd, stdout=subprocess.PIPE) as proc:
                     recent_file = None
                     for line in proc.stdout:
                         if line.isspace():
@@ -80,6 +81,9 @@ def run(files):
                                 filtered_lines.append(recent_file)
                                 recent_file = None
                             filtered_lines.append(line)
+                    proc.wait()
+                    if proc.returncode:
+                        raise PreprocessorError("command failed: " + " ".join(cmd))
                 return b"".join(filtered_lines)
             except subprocess.CalledProcessError as er:
                 raise PreprocessorError(str(er))
