From d0a989debc23ddeb692c120fb4aa5b8568e3c754 Mon Sep 17 00:00:00 2001
From: Stefan Monnier <monnier@iro.umontreal.ca>
Date: Sat, 3 Sep 2022 10:51:17 -0400
Subject: [PATCH] * lisp/emacs-lisp/comp.el (comp-run-async-workers): Fail more
 gracefully

Otherwise Emacs may fail to start if it can't find a writable
`~/.emacs.d/eln-cache` directory.
See Debian's bug #1017739.
---
 lisp/emacs-lisp/comp.el | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index 306ec918b1a..6e2564236db 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -1370,19 +1370,22 @@ comp-spill-lap-function
   (unless byte-to-native-top-level-forms
     (signal 'native-compiler-error-empty-byte filename))
   (unless (comp-ctxt-output comp-ctxt)
-    (setf (comp-ctxt-output comp-ctxt) (comp-el-to-eln-filename
-                                        filename
-                                        (or native-compile-target-directory
-                                            (when byte+native-compile
-                                              (car (last native-comp-eln-load-path)))))))
+    (setf (comp-ctxt-output comp-ctxt)
+          (comp-el-to-eln-filename
+           filename
+           (or native-compile-target-directory
+               (when byte+native-compile
+                 (car (last native-comp-eln-load-path)))))))
   (setf (comp-ctxt-speed comp-ctxt) (alist-get 'native-comp-speed
                                                byte-native-qualities)
         (comp-ctxt-debug comp-ctxt) (alist-get 'native-comp-debug
                                                byte-native-qualities)
-        (comp-ctxt-compiler-options comp-ctxt) (alist-get 'native-comp-compiler-options
-                                                        byte-native-qualities)
-        (comp-ctxt-driver-options comp-ctxt) (alist-get 'native-comp-driver-options
-                                                        byte-native-qualities)
+        (comp-ctxt-compiler-options comp-ctxt)
+        (alist-get 'native-comp-compiler-options
+                   byte-native-qualities)
+        (comp-ctxt-driver-options comp-ctxt)
+        (alist-get 'native-comp-driver-options
+                   byte-native-qualities)
         (comp-ctxt-top-level-forms comp-ctxt)
         (cl-loop
          for form in (reverse byte-to-native-top-level-forms)
@@ -3933,10 +3936,13 @@ comp-run-async-workers
                        "`comp-files-queue' should be \".el\" files: %s"
                        source-file)
          when (or native-comp-always-compile
-                  load ; Always compile when the compilation is
-                       ; commanded for late load.
-                  (file-newer-than-file-p
-                   source-file (comp-el-to-eln-filename source-file)))
+                  load        ; Always compile when the compilation is
+                              ; commanded for late load.
+                  ;; Skip compilation if `comp-el-to-eln-filename' fails
+                  ;; to find a writable directory.
+                  (with-demoted-errors "Async compilation :%S"
+                    (file-newer-than-file-p
+                     source-file (comp-el-to-eln-filename source-file))))
          do (let* ((expr `((require 'comp)
                            (setq comp-async-compilation t)
                            (setq warning-fill-column most-positive-fixnum)
-- 
2.30.2