GNU bug report logs - #68417
scm_from_stringn throws error regardless of failed conversion handler

Previous Next

To reply to this bug, email your comments to 68417 AT debbugs.gnu.org.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Nate Whetsell <nathan.whetsell <at> gmail.com>
To: bug-guile <at> gnu.org
Subject: scm_from_stringn throws error regardless of failed conversion handler
Date: Fri, 12 Jan 2024 14:11:33 -0500

Here is a test program that defines a Guile extension to convert invalid UTF-8 bytes to a string using each of the failed conversion handlers described at

https://www.gnu.org/software/guile/manual/html_node/Conversion-to_002ffrom-C.html#index-scm_005ft_005fstring_005ffailed_005fconversion_005fhandler

```
#include <libguile.h>

static char str[] = {
  208, 151, 208, 178, 208, 184, 209, 135, 208, 176, 208, 185, 208, 189, 208, 184, 208, 102, 97, 109, 105, 108, 121
};

SCM
error_test (void)
{
  return scm_from_stringn (str, sizeof(str), "UTF-8", SCM_FAILED_CONVERSION_ERROR);
}

SCM
question_mark_test (void)
{
  return scm_from_stringn (str, sizeof(str), "UTF-8", SCM_FAILED_CONVERSION_QUESTION_MARK);
}

SCM
escape_test (void)
{
  return scm_from_stringn (str, sizeof(str), "UTF-8", SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE);
}

void
init_test ()
{
  scm_c_define_gsubr ("conversion-error-test", 0, 0, 0, error_test);
  scm_c_define_gsubr ("conversion-question-mark-test", 0, 0, 0, question_mark_test);
  scm_c_define_gsubr ("conversion-escape-test", 0, 0, 0, escape_test);
}
```

If I compile this program using

```
gcc $(pkg-config --cflags --libs guile-3.0) -shared -o libguile-conversion-test.so -fPIC test.c
```

load the resulting extension into Guile, and run the functions, all of them throw errors. I would expect SCM_FAILED_CONVERSION_ERROR to throw an error, of course, and SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE is documented as being irrelevant to converting C strings to Scheme. However, I would not expect using SCM_FAILED_CONVERSION_QUESTION_MARK to throw a conversion error.

Here is the output I get from Guile:

```
GNU Guile 3.0.9
Copyright (C) 1995-2023 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (load-extension "./libguile-conversion-test.so" "init_test")
scheme@(guile-user)> (conversion-error-test)
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Throw to key `decoding-error' with args `("scm_from_utf8_stringn" "input locale conversion error" 0 #vu8(208 151 208 178 208 184 209 135 208 176 208 185 208 189 208 184 208 102 97 109 105 108 121))'.

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,q
scheme@(guile-user)> (conversion-question-mark-test)
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Throw to key `decoding-error' with args `("scm_from_stringn" "input locale conversion error" 92 #vu8(208 151 208 178 208 184 209 135 208 176 208 185 208 189 208 184 208 102 97 109 105 108 121))'.

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,q
scheme@(guile-user)> (conversion-escape-test)
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Throw to key `decoding-error' with args `("scm_from_stringn" "input locale conversion error" 92 #vu8(208 151 208 178 208 184 209 135 208 176 208 185 208 189 208 184 208 102 97 109 105 108 121))'.

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
```

Note that it is possible to convert those bytes to a string without an error using bytevector->string, which is documented as the Scheme interface to scm_from_stringn:

https://www.gnu.org/software/guile/manual/html_node/Conversion-to_002ffrom-C.html#index-scm_005ffrom_005fstringn

```
scheme@(guile-user)> (use-modules (ice-9 iconv))
scheme@(guile-user)> (bytevector->string #vu8(208 151 208 178 208 184 209 135 208 176 208 185 208 189 208 184 208 102 97 109 105 108 121) "UTF-8" 'substitute)
$1 = "Звичайни�family"
```

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.