Issue #16455: On FreeBSD and Solaris, if the locale is C, the

ASCII/surrogateescape codec is now used, instead of the locale encoding, to
decode the command line arguments. This change fixes inconsistencies with
os.fsencode() and os.fsdecode() because these operating systems announces an
ASCII locale encoding, whereas the ISO-8859-1 encoding is used in practice.

3 files changed, 232 insertions, 27 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index e990e83..fdd372d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,12 @@ What's New in Python 3.2.4
 Core and Builtins
 -----------------
 
+- Issue #16455: On FreeBSD and Solaris, if the locale is C, the
+  ASCII/surrogateescape codec is now used, instead of the locale encoding, to
+  decode the command line arguments. This change fixes inconsistencies with
+  os.fsencode() and os.fsdecode() because these operating systems announces an
+  ASCII locale encoding, whereas the ISO-8859-1 encoding is used in practice.
+
 - Issue #16761: Calling int() with base argument only now raises TypeError.
 
 - Issue #16759: Support the full DWORD (unsigned long) range in Reg2Py
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index bb45b20..f8c738b 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1434,8 +1434,8 @@ PyObject *PyUnicode_FromEncodedObject(register PyObject *obj,
 /* Convert encoding to lower case and replace '_' with '-' in order to
    catch e.g. UTF_8. Return 0 on error (encoding is longer than lower_len-1),
    1 on success. */
-static int
-normalize_encoding(const char *encoding,
+int
+_Py_normalize_encoding(const char *encoding,
                    char *lower,
                    size_t lower_len)
 {
@@ -1477,7 +1477,7 @@ PyObject *PyUnicode_Decode(const char *s,
         encoding = PyUnicode_GetDefaultEncoding();
 
     /* Shortcuts for common default encodings */
-    if (normalize_encoding(encoding, lower, sizeof(lower))) {
+    if (_Py_normalize_encoding(encoding, lower, sizeof(lower))) {
         if (strcmp(lower, "utf-8") == 0)
             return PyUnicode_DecodeUTF8(s, size, errors);
         else if ((strcmp(lower, "latin-1") == 0) ||
@@ -1695,7 +1695,7 @@ PyObject *PyUnicode_AsEncodedString(PyObject *unicode,
         encoding = PyUnicode_GetDefaultEncoding();
 
     /* Shortcuts for common default encodings */
-    if (normalize_encoding(encoding, lower, sizeof(lower))) {
+    if (_Py_normalize_encoding(encoding, lower, sizeof(lower))) {
         if (strcmp(lower, "utf-8") == 0)
             return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
                                         PyUnicode_GET_SIZE(unicode),
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 94ab8e4..53e8a47 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -3,11 +3,191 @@
 #  include <windows.h>
 #endif
 
+#ifdef HAVE_LANGINFO_H
+#include <locale.h>
+#include <langinfo.h>
+#endif
+
 #ifdef __APPLE__
 extern wchar_t* _Py_DecodeUTF8_surrogateescape(const char *s, Py_ssize_t size);
 #endif
 
-#ifdef HAVE_STAT
+#if !defined(__APPLE__) && !defined(MS_WINDOWS)
+extern int _Py_normalize_encoding(const char *, char *, size_t);
+
+/* Workaround FreeBSD and OpenIndiana locale encoding issue with the C locale.
+   On these operating systems, nl_langinfo(CODESET) announces an alias of the
+   ASCII encoding, whereas mbstowcs() and wcstombs() functions use the
+   ISO-8859-1 encoding. The problem is that os.fsencode() and os.fsdecode() use
+   locale.getpreferredencoding() codec. For example, if command line arguments
+   are decoded by mbstowcs() and encoded back by os.fsencode(), we get a
+   UnicodeEncodeError instead of retrieving the original byte string.
+
+   The workaround is enabled if setlocale(LC_CTYPE, NULL) returns "C",
+   nl_langinfo(CODESET) announces "ascii" (or an alias to ASCII), and at least
+   one byte in range 0x80-0xff can be decoded from the locale encoding. The
+   workaround is also enabled on error, for example if getting the locale
+   failed.
+
+   Values of locale_is_ascii:
+
+       1: the workaround is used: _Py_wchar2char() uses
+          encode_ascii_surrogateescape() and _Py_char2wchar() uses
+          decode_ascii_surrogateescape()
+       0: the workaround is not used: _Py_wchar2char() uses wcstombs() and
+          _Py_char2wchar() uses mbstowcs()
+      -1: unknown, need to call check_force_ascii() to get the value
+*/
+static int force_ascii = -1;
+
+static int
+check_force_ascii(void)
+{
+    char *loc;
+#if defined(HAVE_LANGINFO_H) && defined(CODESET)
+    char *codeset, **alias;
+    char encoding[100];
+    int is_ascii;
+    unsigned int i;
+    char* ascii_aliases[] = {
+        "ascii",
+        "646",
+        "ansi-x3.4-1968",
+        "ansi-x3-4-1968",
+        "ansi-x3.4-1986",
+        "cp367",
+        "csascii",
+        "ibm367",
+        "iso646-us",
+        "iso-646.irv-1991",
+        "iso-ir-6",
+        "us",
+        "us-ascii",
+        NULL
+    };
+#endif
+
+    loc = setlocale(LC_CTYPE, NULL);
+    if (loc == NULL)
+        goto error;
+    if (strcmp(loc, "C") != 0) {
+        /* the LC_CTYPE locale is different than C */
+        return 0;
+    }
+
+#if defined(HAVE_LANGINFO_H) && defined(CODESET)
+    codeset = nl_langinfo(CODESET);
+    if (!codeset || codeset[0] == '\0') {
+        /* CODESET is not set or empty */
+        goto error;
+    }
+    if (!_Py_normalize_encoding(codeset, encoding, sizeof(encoding)))
+        goto error;
+
+    is_ascii = 0;
+    for (alias=ascii_aliases; *alias != NULL; alias++) {
+        if (strcmp(encoding, *alias) == 0) {
+            is_ascii = 1;
+            break;
+        }
+    }
+    if (!is_ascii) {
+        /* nl_langinfo(CODESET) is not "ascii" or an alias of ASCII */
+        return 0;
+    }
+
+    for (i=0x80; i<0xff; i++) {
+        unsigned char ch;
+        wchar_t wch;
+        size_t res;
+
+        ch = (unsigned char)i;
+        res = mbstowcs(&wch, (char*)&ch, 1);
+        if (res != (size_t)-1) {
+            /* decoding a non-ASCII character from the locale encoding succeed:
+               the locale encoding is not ASCII, force ASCII */
+            return 1;
+        }
+    }
+    /* None of the bytes in the range 0x80-0xff can be decoded from the locale
+       encoding: the locale encoding is really ASCII */
+    return 0;
+#else
+    /* nl_langinfo(CODESET) is not available: always force ASCII */
+    return 1;
+#endif
+
+error:
+    /* if an error occured, force the ASCII encoding */
+    return 1;
+}
+
+static char*
+encode_ascii_surrogateescape(const wchar_t *text, size_t *error_pos)
+{
+    char *result = NULL, *out;
+    size_t len, i;
+    wchar_t ch;
+
+    if (error_pos != NULL)
+        *error_pos = (size_t)-1;
+
+    len = wcslen(text);
+
+    result = PyMem_Malloc(len + 1);  /* +1 for NUL byte */
+    if (result == NULL)
+        return NULL;
+
+    out = result;
+    for (i=0; i<len; i++) {
+        ch = text[i];
+
+        if (ch <= 0x7f) {
+            /* ASCII character */
+            *out++ = (char)ch;
+        }
+        else if (0xdc80 <= ch && ch <= 0xdcff) {
+            /* UTF-8b surrogate */
+            *out++ = (char)(ch - 0xdc00);
+        }
+        else {
+            if (error_pos != NULL)
+                *error_pos = i;
+            PyMem_Free(result);
+            return NULL;
+        }
+    }
+    *out = '\0';
+    return result;
+}
+#endif   /* !defined(__APPLE__) && !defined(MS_WINDOWS) */
+
+#if !defined(__APPLE__) && (!defined(MS_WINDOWS) || !defined(HAVE_MBRTOWC))
+static wchar_t*
+decode_ascii_surrogateescape(const char *arg, size_t *size)
+{
+    wchar_t *res;
+    unsigned char *in;
+    wchar_t *out;
+
+    res = PyMem_Malloc((strlen(arg)+1)*sizeof(wchar_t));
+    if (!res)
+        return NULL;
+
+    in = (unsigned char*)arg;
+    out = res;
+    while(*in)
+        if(*in < 128)
+            *out++ = *in++;
+        else
+            *out++ = 0xdc00 + *in++;
+    *out = 0;
+    if (size != NULL)
+        *size = out - res;
+    return res;
+}
+#endif
+
 
 /* Decode a byte string from the locale encoding with the
    surrogateescape error handler (undecodable bytes are decoded as characters
@@ -39,20 +219,35 @@ _Py_char2wchar(const char* arg, size_t *size)
     return wstr;
 #else
     wchar_t *res;
+    size_t argsize;
+    size_t count;
+    unsigned char *in;
+    wchar_t *out;
+#ifdef HAVE_MBRTOWC
+    mbstate_t mbs;
+#endif
+
+#ifndef MS_WINDOWS
+    if (force_ascii == -1)
+        force_ascii = check_force_ascii();
+
+    if (force_ascii) {
+        /* force ASCII encoding to workaround mbstowcs() issue */
+        res = decode_ascii_surrogateescape(arg, size);
+        if (res == NULL)
+            goto oom;
+        return res;
+    }
+#endif
+
 #ifdef HAVE_BROKEN_MBSTOWCS
     /* Some platforms have a broken implementation of
      * mbstowcs which does not count the characters that
      * would result from conversion.  Use an upper bound.
      */
-    size_t argsize = strlen(arg);
+    argsize = strlen(arg);
 #else
-    size_t argsize = mbstowcs(NULL, arg, 0);
-#endif
-    size_t count;
-    unsigned char *in;
-    wchar_t *out;
-#ifdef HAVE_MBRTOWC
-    mbstate_t mbs;
+    argsize = mbstowcs(NULL, arg, 0);
 #endif
     if (argsize != (size_t)-1) {
         res = (wchar_t *)PyMem_Malloc((argsize+1)*sizeof(wchar_t));
@@ -122,23 +317,16 @@ _Py_char2wchar(const char* arg, size_t *size)
         argsize -= converted;
         out++;
     }
+    if (size != NULL)
+        *size = out - res;
 #else   /* HAVE_MBRTOWC */
     /* Cannot use C locale for escaping; manually escape as if charset
        is ASCII (i.e. escape all bytes > 128. This will still roundtrip
        correctly in the locale's charset, which must be an ASCII superset. */
-    res = PyMem_Malloc((strlen(arg)+1)*sizeof(wchar_t));
-    if (!res) goto oom;
-    in = (unsigned char*)arg;
-    out = res;
-    while(*in)
-        if(*in < 128)
-            *out++ = *in++;
-        else
-            *out++ = 0xdc00 + *in++;
-    *out = 0;
+    res = decode_ascii_surrogateescape(arg, size);
+    if (res == NULL)
+        goto oom;
 #endif   /* HAVE_MBRTOWC */
-    if (size != NULL)
-        *size = out - res;
     return res;
 oom:
     fprintf(stderr, "out of memory\n");
@@ -198,6 +386,14 @@ _Py_wchar2char(const wchar_t *text, size_t *error_pos)
     size_t i, size, converted;
     wchar_t c, buf[2];
 
+#ifndef MS_WINDOWS
+    if (force_ascii == -1)
+        force_ascii = check_force_ascii();
+
+    if (force_ascii)
+        return encode_ascii_surrogateescape(text, error_pos);
+#endif
+
     /* The function works in two steps:
        1. compute the length of the output buffer in bytes (size)
        2. outputs the bytes */
@@ -238,7 +434,7 @@ _Py_wchar2char(const wchar_t *text, size_t *error_pos)
             }
         }
         if (result != NULL) {
-            *bytes = 0;
+            *bytes = '\0';
             break;
         }
 
@@ -282,6 +478,8 @@ _Py_wstat(const wchar_t* path, struct stat *buf)
 }
 #endif
 
+#ifdef HAVE_STAT
+
 /* Call _wstat() on Windows, or encode the path to the filesystem encoding and
    call stat() otherwise. Only fill st_mode attribute on Windows.
 
@@ -310,6 +508,8 @@ _Py_stat(PyObject *path, struct stat *statbuf)
 #endif
 }
 
+#endif
+
 /* Open a file. Use _wfopen() on Windows, encode the path to the locale
    encoding and use fopen() otherwise. */
 
@@ -478,4 +678,3 @@ _Py_wgetcwd(wchar_t *buf, size_t size)
 #endif
 }
 
-#endif