bug#68546: 29.1.90; end-of-file has incorrect data when signaled within a load

[Spencer Baugh]

Here is a straightforward fix.

>From d850108fa309701e4899dfbcfd5a20d1e17f86af Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@janestreet.com>
Date: Fri, 16 Feb 2024 16:53:28 -0500
Subject: [PATCH] Prevent incorrect error message when calling read inside load

Previously, if `load' eval'd a `read' expression which raised
end-of-file, the error would include load-true-file-name, even
though the `read' may be reading something completely different.

Now, end-of-file errors raised by `read' will only include
load-true-file-name if it's actually reading that file.

We do this by having read include read-end-of-file-name in the error
instead of load-true-file-name, and only binding read-end-of-file-name
around the "read" parts of readevalloop, not the "eval" parts.
(load-true-file-name is still bound throughout)

Also, when reading a file (or some other source), it is now
possible to bind read-end-of-file-name so that end-of-file
errors raised by read will include the filename (or the string
of your choice).  Previously, an end-of-file error raised by
read outside of load would never include the filename.

* src/lread.c (syms_of_lread): Add read-end-of-file-name.
(readevalloop): Bind read-end-of-file-name to
load-true-file-name around read.
(end_of_file_error): Use read-end-of-file-name instead of
load-true-file-name.  (bug#68546)
---
 src/lread.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/lread.c b/src/lread.c
index 0e67a3f8879..54ae88c7eab 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2385,8 +2385,8 @@ readevalloop_1 (int old)
 static AVOID
 end_of_file_error (void)
 {
-  if (STRINGP (Vload_true_file_name))
-    xsignal1 (Qend_of_file, Vload_true_file_name);
+  if (!NILP (Vread_end_of_file_name))
+    xsignal1 (Qend_of_file, Vread_end_of_file_name);
 
   xsignal0 (Qend_of_file);
 }
@@ -2490,6 +2490,8 @@ readevalloop (Lisp_Object readcharfun,
   while (continue_reading_p)
     {
       specpdl_ref count1 = SPECPDL_INDEX ();
+      if (NILP (Vread_end_of_file_name))
+       specbind (Qread_end_of_file_name, Vload_true_file_name);
 
       if (b != 0 && !BUFFER_LIVE_P (b))
        error ("Reading from killed buffer");
@@ -2585,7 +2587,7 @@ readevalloop (Lisp_Object readcharfun,
       if (!NILP (start) && continue_reading_p)
        start = Fpoint_marker ();
 
-      /* Restore saved point and BEGV.  */
+      /* Restore saved point and BEGV, and unbind read_stream_for_error.  */
       unbind_to (count1, Qnil);
 
       /* Now eval what we just read.  */
@@ -5843,6 +5845,12 @@ syms_of_lread (void)
               doc: /* Full name of file being loaded by `load'.  */);
   Vload_true_file_name = Qnil;
 
+  DEFVAR_LISP ("read-end-of-file-name", Vread_end_of_file_name,
+              doc: /* String to be included when `read' signals `end-of-file'.
+When loading a file, this is bound to the filename.  */);
+  Vread_end_of_file_name = Qnil;
+  DEFSYM (Qread_end_of_file_name, "read-end-of-file-name");
+
   DEFVAR_LISP ("user-init-file", Vuser_init_file,
               doc: /* File name, including directory, of user's initialization 
file.
 If the file loaded had extension `.elc', and the corresponding source file
-- 
2.39.3