* libguile/ports.c (scm_read_char): Mention `decoding-error' in the
docstring.
(get_codepoint): Change to return an error code; add `codepoint'
output parameter. Don't raise an error from here.
(scm_getc): Raise an error with `scm_decoding_error' if
`get_codepoint' returns an error.
(scm_peek_char): Likewise. Update docstring.
* libguile/strings.c (scm_decoding_error_key): New variable.
(scm_decoding_error): New function.
(scm_from_stringn): Use `scm_decoding_error' instead of
`scm_encoding_error'.
* libguile/strings.h (scm_decoding_error): New declaration.
* test-suite/tests/ports.test ("string ports")["read-char, wrong
encoding, error"]: Change to expect `decoding-error'. Make sure PORT
points past the error.
["read-char, wrong encoding, escape"]: Likewise.
["peek-char, wrong encoding, error"]: New test.
* test-suite/tests/r6rs-ports.test ("7.2.11 Binary
Output")["put-bytevector with wrong-encoding string port"]: Change to
expect `decoding-error'.
("8.2.6 Input and output ports")["transcoded-port [error handling
mode = raise]"]: Likewise.
* test-suite/tests/rdelim.test ("read-line")["decoding error", "decoding
error, substitute"]: New tests.
* doc/ref/api-io.texi (Reading): Update documentation of `read-char' and
`peek-char'.
(Line/Delimited): Update documentation of `read-line'.
As a result `read-line' handles decoding and decoding errors the same
way as `scm_getc'. It's also simpler and free of `malloc' calls.
* libguile/rdelim.c (scm_do_read_line): Remove.
(scm_read_line): Rewrite as a loop that calls `scm_getc'.
* test-suite/tests/rdelim.test: New file.
* test-suite/Makefile.am (SCM_TESTS): Add `tests/rdelim.test'.
