Fix decoding ASCII strings with embedded CR characters

* src/coding.c (string_ascii_p): Return a negative value if an
all-ASCII string STR includes the CR character, otherwise a
positive value.
(code_convert_string): If the string is ASCII, but includes CR
characters, use the fast path only if EOL doesn't need to be
decoded.  (Bug#40519)

* test/src/coding-tests.el (coding-nocopy-ascii): Add tests for
bug#40519.

1 files changed, 17 insertions, 0 deletions

diff --git a/test/src/coding-tests.el b/test/src/coding-tests.el
index 93e6709d442..83a06b8179e 100644
--- a/test/src/coding-tests.el
+++ b/test/src/coding-tests.el
@@ -388,6 +388,23 @@
   (let* ((uni (apply #'string (number-sequence 0 127)))
          (multi (string-to-multibyte uni)))
     (dolist (s (list uni multi))
+      (dolist (coding '(us-ascii-unix iso-latin-1-unix utf-8-unix))
+        (should-not (eq (decode-coding-string s coding nil) s))
+        (should-not (eq (encode-coding-string s coding nil) s))
+        (should (eq (decode-coding-string s coding t) s))
+        (should (eq (encode-coding-string s coding t) s)))))
+  (let* ((uni (apply #'string (number-sequence 15 127)))
+         (multi (string-to-multibyte uni)))
+    (dolist (s (list uni multi))
+      (dolist (coding '(us-ascii iso-latin-1 utf-8))
+        (should-not (eq (decode-coding-string s coding nil) s))
+        (should-not (eq (encode-coding-string s coding nil) s))
+        (should (eq (decode-coding-string s coding t) s))
+        (should (eq (encode-coding-string s coding t) s)))))
+  (let* ((uni (apply #'string (number-sequence 0 127)))
+         (multi (string-to-multibyte uni))
+         (inhibit-eol-conversion t))
+    (dolist (s (list uni multi))
       (dolist (coding '(us-ascii iso-latin-1 utf-8))
         (should-not (eq (decode-coding-string s coding nil) s))
         (should-not (eq (encode-coding-string s coding nil) s))