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Date: Mon, 12 Jun 2023 16:22:42 -0400
From: Rich Felker <dalias@...c.org>
To: Bruno Haible <bruno@...sp.org>
Cc: musl@...ts.openwall.com
Subject: Re: swprintf cannot handle the character 0xff
On Mon, Jun 12, 2023 at 02:30:44PM +0200, Bruno Haible wrote:
> When swprintf is meant to convert a character to a wide character, through
> the %c directive, it fails if that character is '\xff'.
>
> Seen with musl libc 1.2.4, in Alpine Linux 3.18.0.
>
> How to reproduce:
> ============================ foo.c ============================
> #include <stdio.h>
> #include <wchar.h>
> int main ()
> {
> wchar_t buf[12];
> for (int c = 1; c < 256; c++)
> {
> fprintf (stderr, "c = %d: ", c);
> int ret = swprintf (buf, 12, L"%c", c);
> if (ret >= 0)
> fprintf (stderr, "OK, %d bytes\n", ret);
> else
> perror ("swprintf failed");
> }
> }
> ===============================================================
> $ gcc -Wall foo.c
> $ ./a.out
>
> Expected output:
> c = 1: OK, 1 bytes
> c = 2: OK, 1 bytes
> c = 3: OK, 1 bytes
> c = 4: OK, 1 bytes
> c = 5: OK, 1 bytes
> c = 6: OK, 1 bytes
> c = 7: OK, 1 bytes
> c = 8: OK, 1 bytes
> c = 9: OK, 1 bytes
> c = 10: OK, 1 bytes
> c = 11: OK, 1 bytes
> c = 12: OK, 1 bytes
> c = 13: OK, 1 bytes
> c = 14: OK, 1 bytes
> c = 15: OK, 1 bytes
> c = 16: OK, 1 bytes
> c = 17: OK, 1 bytes
> c = 18: OK, 1 bytes
> c = 19: OK, 1 bytes
> c = 20: OK, 1 bytes
> c = 21: OK, 1 bytes
> c = 22: OK, 1 bytes
> c = 23: OK, 1 bytes
> c = 24: OK, 1 bytes
> c = 25: OK, 1 bytes
> c = 26: OK, 1 bytes
> c = 27: OK, 1 bytes
> c = 28: OK, 1 bytes
> c = 29: OK, 1 bytes
> c = 30: OK, 1 bytes
> c = 31: OK, 1 bytes
> c = 32: OK, 1 bytes
> c = 33: OK, 1 bytes
> c = 34: OK, 1 bytes
> c = 35: OK, 1 bytes
> c = 36: OK, 1 bytes
> c = 37: OK, 1 bytes
> c = 38: OK, 1 bytes
> c = 39: OK, 1 bytes
> c = 40: OK, 1 bytes
> c = 41: OK, 1 bytes
> c = 42: OK, 1 bytes
> c = 43: OK, 1 bytes
> c = 44: OK, 1 bytes
> c = 45: OK, 1 bytes
> c = 46: OK, 1 bytes
> c = 47: OK, 1 bytes
> c = 48: OK, 1 bytes
> c = 49: OK, 1 bytes
> c = 50: OK, 1 bytes
> c = 51: OK, 1 bytes
> c = 52: OK, 1 bytes
> c = 53: OK, 1 bytes
> c = 54: OK, 1 bytes
> c = 55: OK, 1 bytes
> c = 56: OK, 1 bytes
> c = 57: OK, 1 bytes
> c = 58: OK, 1 bytes
> c = 59: OK, 1 bytes
> c = 60: OK, 1 bytes
> c = 61: OK, 1 bytes
> c = 62: OK, 1 bytes
> c = 63: OK, 1 bytes
> c = 64: OK, 1 bytes
> c = 65: OK, 1 bytes
> c = 66: OK, 1 bytes
> c = 67: OK, 1 bytes
> c = 68: OK, 1 bytes
> c = 69: OK, 1 bytes
> c = 70: OK, 1 bytes
> c = 71: OK, 1 bytes
> c = 72: OK, 1 bytes
> c = 73: OK, 1 bytes
> c = 74: OK, 1 bytes
> c = 75: OK, 1 bytes
> c = 76: OK, 1 bytes
> c = 77: OK, 1 bytes
> c = 78: OK, 1 bytes
> c = 79: OK, 1 bytes
> c = 80: OK, 1 bytes
> c = 81: OK, 1 bytes
> c = 82: OK, 1 bytes
> c = 83: OK, 1 bytes
> c = 84: OK, 1 bytes
> c = 85: OK, 1 bytes
> c = 86: OK, 1 bytes
> c = 87: OK, 1 bytes
> c = 88: OK, 1 bytes
> c = 89: OK, 1 bytes
> c = 90: OK, 1 bytes
> c = 91: OK, 1 bytes
> c = 92: OK, 1 bytes
> c = 93: OK, 1 bytes
> c = 94: OK, 1 bytes
> c = 95: OK, 1 bytes
> c = 96: OK, 1 bytes
> c = 97: OK, 1 bytes
> c = 98: OK, 1 bytes
> c = 99: OK, 1 bytes
> c = 100: OK, 1 bytes
> c = 101: OK, 1 bytes
> c = 102: OK, 1 bytes
> c = 103: OK, 1 bytes
> c = 104: OK, 1 bytes
> c = 105: OK, 1 bytes
> c = 106: OK, 1 bytes
> c = 107: OK, 1 bytes
> c = 108: OK, 1 bytes
> c = 109: OK, 1 bytes
> c = 110: OK, 1 bytes
> c = 111: OK, 1 bytes
> c = 112: OK, 1 bytes
> c = 113: OK, 1 bytes
> c = 114: OK, 1 bytes
> c = 115: OK, 1 bytes
> c = 116: OK, 1 bytes
> c = 117: OK, 1 bytes
> c = 118: OK, 1 bytes
> c = 119: OK, 1 bytes
> c = 120: OK, 1 bytes
> c = 121: OK, 1 bytes
> c = 122: OK, 1 bytes
> c = 123: OK, 1 bytes
> c = 124: OK, 1 bytes
> c = 125: OK, 1 bytes
> c = 126: OK, 1 bytes
> c = 127: OK, 1 bytes
> c = 128: OK, 1 bytes
> c = 129: OK, 1 bytes
> c = 130: OK, 1 bytes
> c = 131: OK, 1 bytes
> c = 132: OK, 1 bytes
> c = 133: OK, 1 bytes
> c = 134: OK, 1 bytes
> c = 135: OK, 1 bytes
> c = 136: OK, 1 bytes
> c = 137: OK, 1 bytes
> c = 138: OK, 1 bytes
> c = 139: OK, 1 bytes
> c = 140: OK, 1 bytes
> c = 141: OK, 1 bytes
> c = 142: OK, 1 bytes
> c = 143: OK, 1 bytes
> c = 144: OK, 1 bytes
> c = 145: OK, 1 bytes
> c = 146: OK, 1 bytes
> c = 147: OK, 1 bytes
> c = 148: OK, 1 bytes
> c = 149: OK, 1 bytes
> c = 150: OK, 1 bytes
> c = 151: OK, 1 bytes
> c = 152: OK, 1 bytes
> c = 153: OK, 1 bytes
> c = 154: OK, 1 bytes
> c = 155: OK, 1 bytes
> c = 156: OK, 1 bytes
> c = 157: OK, 1 bytes
> c = 158: OK, 1 bytes
> c = 159: OK, 1 bytes
> c = 160: OK, 1 bytes
> c = 161: OK, 1 bytes
> c = 162: OK, 1 bytes
> c = 163: OK, 1 bytes
> c = 164: OK, 1 bytes
> c = 165: OK, 1 bytes
> c = 166: OK, 1 bytes
> c = 167: OK, 1 bytes
> c = 168: OK, 1 bytes
> c = 169: OK, 1 bytes
> c = 170: OK, 1 bytes
> c = 171: OK, 1 bytes
> c = 172: OK, 1 bytes
> c = 173: OK, 1 bytes
> c = 174: OK, 1 bytes
> c = 175: OK, 1 bytes
> c = 176: OK, 1 bytes
> c = 177: OK, 1 bytes
> c = 178: OK, 1 bytes
> c = 179: OK, 1 bytes
> c = 180: OK, 1 bytes
> c = 181: OK, 1 bytes
> c = 182: OK, 1 bytes
> c = 183: OK, 1 bytes
> c = 184: OK, 1 bytes
> c = 185: OK, 1 bytes
> c = 186: OK, 1 bytes
> c = 187: OK, 1 bytes
> c = 188: OK, 1 bytes
> c = 189: OK, 1 bytes
> c = 190: OK, 1 bytes
> c = 191: OK, 1 bytes
> c = 192: OK, 1 bytes
> c = 193: OK, 1 bytes
> c = 194: OK, 1 bytes
> c = 195: OK, 1 bytes
> c = 196: OK, 1 bytes
> c = 197: OK, 1 bytes
> c = 198: OK, 1 bytes
> c = 199: OK, 1 bytes
> c = 200: OK, 1 bytes
> c = 201: OK, 1 bytes
> c = 202: OK, 1 bytes
> c = 203: OK, 1 bytes
> c = 204: OK, 1 bytes
> c = 205: OK, 1 bytes
> c = 206: OK, 1 bytes
> c = 207: OK, 1 bytes
> c = 208: OK, 1 bytes
> c = 209: OK, 1 bytes
> c = 210: OK, 1 bytes
> c = 211: OK, 1 bytes
> c = 212: OK, 1 bytes
> c = 213: OK, 1 bytes
> c = 214: OK, 1 bytes
> c = 215: OK, 1 bytes
> c = 216: OK, 1 bytes
> c = 217: OK, 1 bytes
> c = 218: OK, 1 bytes
> c = 219: OK, 1 bytes
> c = 220: OK, 1 bytes
> c = 221: OK, 1 bytes
> c = 222: OK, 1 bytes
> c = 223: OK, 1 bytes
> c = 224: OK, 1 bytes
> c = 225: OK, 1 bytes
> c = 226: OK, 1 bytes
> c = 227: OK, 1 bytes
> c = 228: OK, 1 bytes
> c = 229: OK, 1 bytes
> c = 230: OK, 1 bytes
> c = 231: OK, 1 bytes
> c = 232: OK, 1 bytes
> c = 233: OK, 1 bytes
> c = 234: OK, 1 bytes
> c = 235: OK, 1 bytes
> c = 236: OK, 1 bytes
> c = 237: OK, 1 bytes
> c = 238: OK, 1 bytes
> c = 239: OK, 1 bytes
> c = 240: OK, 1 bytes
> c = 241: OK, 1 bytes
> c = 242: OK, 1 bytes
> c = 243: OK, 1 bytes
> c = 244: OK, 1 bytes
> c = 245: OK, 1 bytes
> c = 246: OK, 1 bytes
> c = 247: OK, 1 bytes
> c = 248: OK, 1 bytes
> c = 249: OK, 1 bytes
> c = 250: OK, 1 bytes
> c = 251: OK, 1 bytes
> c = 252: OK, 1 bytes
> c = 253: OK, 1 bytes
> c = 254: OK, 1 bytes
> c = 255: OK, 1 bytes
>
> Actual output:
> c = 1: OK, 1 bytes
> c = 2: OK, 1 bytes
> c = 3: OK, 1 bytes
> c = 4: OK, 1 bytes
> c = 5: OK, 1 bytes
> c = 6: OK, 1 bytes
> c = 7: OK, 1 bytes
> c = 8: OK, 1 bytes
> c = 9: OK, 1 bytes
> c = 10: OK, 1 bytes
> c = 11: OK, 1 bytes
> c = 12: OK, 1 bytes
> c = 13: OK, 1 bytes
> c = 14: OK, 1 bytes
> c = 15: OK, 1 bytes
> c = 16: OK, 1 bytes
> c = 17: OK, 1 bytes
> c = 18: OK, 1 bytes
> c = 19: OK, 1 bytes
> c = 20: OK, 1 bytes
> c = 21: OK, 1 bytes
> c = 22: OK, 1 bytes
> c = 23: OK, 1 bytes
> c = 24: OK, 1 bytes
> c = 25: OK, 1 bytes
> c = 26: OK, 1 bytes
> c = 27: OK, 1 bytes
> c = 28: OK, 1 bytes
> c = 29: OK, 1 bytes
> c = 30: OK, 1 bytes
> c = 31: OK, 1 bytes
> c = 32: OK, 1 bytes
> c = 33: OK, 1 bytes
> c = 34: OK, 1 bytes
> c = 35: OK, 1 bytes
> c = 36: OK, 1 bytes
> c = 37: OK, 1 bytes
> c = 38: OK, 1 bytes
> c = 39: OK, 1 bytes
> c = 40: OK, 1 bytes
> c = 41: OK, 1 bytes
> c = 42: OK, 1 bytes
> c = 43: OK, 1 bytes
> c = 44: OK, 1 bytes
> c = 45: OK, 1 bytes
> c = 46: OK, 1 bytes
> c = 47: OK, 1 bytes
> c = 48: OK, 1 bytes
> c = 49: OK, 1 bytes
> c = 50: OK, 1 bytes
> c = 51: OK, 1 bytes
> c = 52: OK, 1 bytes
> c = 53: OK, 1 bytes
> c = 54: OK, 1 bytes
> c = 55: OK, 1 bytes
> c = 56: OK, 1 bytes
> c = 57: OK, 1 bytes
> c = 58: OK, 1 bytes
> c = 59: OK, 1 bytes
> c = 60: OK, 1 bytes
> c = 61: OK, 1 bytes
> c = 62: OK, 1 bytes
> c = 63: OK, 1 bytes
> c = 64: OK, 1 bytes
> c = 65: OK, 1 bytes
> c = 66: OK, 1 bytes
> c = 67: OK, 1 bytes
> c = 68: OK, 1 bytes
> c = 69: OK, 1 bytes
> c = 70: OK, 1 bytes
> c = 71: OK, 1 bytes
> c = 72: OK, 1 bytes
> c = 73: OK, 1 bytes
> c = 74: OK, 1 bytes
> c = 75: OK, 1 bytes
> c = 76: OK, 1 bytes
> c = 77: OK, 1 bytes
> c = 78: OK, 1 bytes
> c = 79: OK, 1 bytes
> c = 80: OK, 1 bytes
> c = 81: OK, 1 bytes
> c = 82: OK, 1 bytes
> c = 83: OK, 1 bytes
> c = 84: OK, 1 bytes
> c = 85: OK, 1 bytes
> c = 86: OK, 1 bytes
> c = 87: OK, 1 bytes
> c = 88: OK, 1 bytes
> c = 89: OK, 1 bytes
> c = 90: OK, 1 bytes
> c = 91: OK, 1 bytes
> c = 92: OK, 1 bytes
> c = 93: OK, 1 bytes
> c = 94: OK, 1 bytes
> c = 95: OK, 1 bytes
> c = 96: OK, 1 bytes
> c = 97: OK, 1 bytes
> c = 98: OK, 1 bytes
> c = 99: OK, 1 bytes
> c = 100: OK, 1 bytes
> c = 101: OK, 1 bytes
> c = 102: OK, 1 bytes
> c = 103: OK, 1 bytes
> c = 104: OK, 1 bytes
> c = 105: OK, 1 bytes
> c = 106: OK, 1 bytes
> c = 107: OK, 1 bytes
> c = 108: OK, 1 bytes
> c = 109: OK, 1 bytes
> c = 110: OK, 1 bytes
> c = 111: OK, 1 bytes
> c = 112: OK, 1 bytes
> c = 113: OK, 1 bytes
> c = 114: OK, 1 bytes
> c = 115: OK, 1 bytes
> c = 116: OK, 1 bytes
> c = 117: OK, 1 bytes
> c = 118: OK, 1 bytes
> c = 119: OK, 1 bytes
> c = 120: OK, 1 bytes
> c = 121: OK, 1 bytes
> c = 122: OK, 1 bytes
> c = 123: OK, 1 bytes
> c = 124: OK, 1 bytes
> c = 125: OK, 1 bytes
> c = 126: OK, 1 bytes
> c = 127: OK, 1 bytes
> c = 128: OK, 1 bytes
> c = 129: OK, 1 bytes
> c = 130: OK, 1 bytes
> c = 131: OK, 1 bytes
> c = 132: OK, 1 bytes
> c = 133: OK, 1 bytes
> c = 134: OK, 1 bytes
> c = 135: OK, 1 bytes
> c = 136: OK, 1 bytes
> c = 137: OK, 1 bytes
> c = 138: OK, 1 bytes
> c = 139: OK, 1 bytes
> c = 140: OK, 1 bytes
> c = 141: OK, 1 bytes
> c = 142: OK, 1 bytes
> c = 143: OK, 1 bytes
> c = 144: OK, 1 bytes
> c = 145: OK, 1 bytes
> c = 146: OK, 1 bytes
> c = 147: OK, 1 bytes
> c = 148: OK, 1 bytes
> c = 149: OK, 1 bytes
> c = 150: OK, 1 bytes
> c = 151: OK, 1 bytes
> c = 152: OK, 1 bytes
> c = 153: OK, 1 bytes
> c = 154: OK, 1 bytes
> c = 155: OK, 1 bytes
> c = 156: OK, 1 bytes
> c = 157: OK, 1 bytes
> c = 158: OK, 1 bytes
> c = 159: OK, 1 bytes
> c = 160: OK, 1 bytes
> c = 161: OK, 1 bytes
> c = 162: OK, 1 bytes
> c = 163: OK, 1 bytes
> c = 164: OK, 1 bytes
> c = 165: OK, 1 bytes
> c = 166: OK, 1 bytes
> c = 167: OK, 1 bytes
> c = 168: OK, 1 bytes
> c = 169: OK, 1 bytes
> c = 170: OK, 1 bytes
> c = 171: OK, 1 bytes
> c = 172: OK, 1 bytes
> c = 173: OK, 1 bytes
> c = 174: OK, 1 bytes
> c = 175: OK, 1 bytes
> c = 176: OK, 1 bytes
> c = 177: OK, 1 bytes
> c = 178: OK, 1 bytes
> c = 179: OK, 1 bytes
> c = 180: OK, 1 bytes
> c = 181: OK, 1 bytes
> c = 182: OK, 1 bytes
> c = 183: OK, 1 bytes
> c = 184: OK, 1 bytes
> c = 185: OK, 1 bytes
> c = 186: OK, 1 bytes
> c = 187: OK, 1 bytes
> c = 188: OK, 1 bytes
> c = 189: OK, 1 bytes
> c = 190: OK, 1 bytes
> c = 191: OK, 1 bytes
> c = 192: OK, 1 bytes
> c = 193: OK, 1 bytes
> c = 194: OK, 1 bytes
> c = 195: OK, 1 bytes
> c = 196: OK, 1 bytes
> c = 197: OK, 1 bytes
> c = 198: OK, 1 bytes
> c = 199: OK, 1 bytes
> c = 200: OK, 1 bytes
> c = 201: OK, 1 bytes
> c = 202: OK, 1 bytes
> c = 203: OK, 1 bytes
> c = 204: OK, 1 bytes
> c = 205: OK, 1 bytes
> c = 206: OK, 1 bytes
> c = 207: OK, 1 bytes
> c = 208: OK, 1 bytes
> c = 209: OK, 1 bytes
> c = 210: OK, 1 bytes
> c = 211: OK, 1 bytes
> c = 212: OK, 1 bytes
> c = 213: OK, 1 bytes
> c = 214: OK, 1 bytes
> c = 215: OK, 1 bytes
> c = 216: OK, 1 bytes
> c = 217: OK, 1 bytes
> c = 218: OK, 1 bytes
> c = 219: OK, 1 bytes
> c = 220: OK, 1 bytes
> c = 221: OK, 1 bytes
> c = 222: OK, 1 bytes
> c = 223: OK, 1 bytes
> c = 224: OK, 1 bytes
> c = 225: OK, 1 bytes
> c = 226: OK, 1 bytes
> c = 227: OK, 1 bytes
> c = 228: OK, 1 bytes
> c = 229: OK, 1 bytes
> c = 230: OK, 1 bytes
> c = 231: OK, 1 bytes
> c = 232: OK, 1 bytes
> c = 233: OK, 1 bytes
> c = 234: OK, 1 bytes
> c = 235: OK, 1 bytes
> c = 236: OK, 1 bytes
> c = 237: OK, 1 bytes
> c = 238: OK, 1 bytes
> c = 239: OK, 1 bytes
> c = 240: OK, 1 bytes
> c = 241: OK, 1 bytes
> c = 242: OK, 1 bytes
> c = 243: OK, 1 bytes
> c = 244: OK, 1 bytes
> c = 245: OK, 1 bytes
> c = 246: OK, 1 bytes
> c = 247: OK, 1 bytes
> c = 248: OK, 1 bytes
> c = 249: OK, 1 bytes
> c = 250: OK, 1 bytes
> c = 251: OK, 1 bytes
> c = 252: OK, 1 bytes
> c = 253: OK, 1 bytes
> c = 254: OK, 1 bytes
> c = 255: swprintf failed: Illegal byte sequence
>
> This is a bug, because POSIX says that in the C / POSIX locale, "all byte
> values are valid characters" [1].
Yes, this is a bug and seems to be an instance of mishandling of
signed conversions. Attached should correct it.
Rich
View attachment "wprintf-255.diff" of type "text/plain" (479 bytes)
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