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Date: Mon, 12 Jun 2023 17:13:36 -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 05:01:59PM -0400, Rich Felker wrote:
> On Mon, Jun 12, 2023 at 04:22:42PM -0400, Rich Felker wrote:
> > 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
>
> > diff --git a/src/stdio/vfwprintf.c b/src/stdio/vfwprintf.c
> > index 53697701..a653e233 100644
> > --- a/src/stdio/vfwprintf.c
> > +++ b/src/stdio/vfwprintf.c
> > @@ -271,7 +271,7 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
> > case 'C':
> > if (w<1) w=1;
> > pad(f, w-1, fl);
> > - out(f, &(wchar_t){t=='C' ? arg.i : btowc(arg.i)}, 1);
> > + out(f, &(wchar_t){t=='C' ? arg.i : btowc(arg.i & 0xff)}, 1);
> > pad(f, w-1, fl^LEFT_ADJ);
> > l = w;
> > continue;
>
> Hmm -- while this works, formally, %c takes an argument of type int
> not char, so I think we should probably actually change the state
> machine for both narrow and wide printf to terminate with state INT
> rather than CHAR for 'c'. And likewise, %lc/%C takes wint_t, which has
> type unsigned, so although it doesn't matter the state machine should
> terminate with state UINT rather than INT (wint_t is unsigned).
And the plot thickens...
For narrow printf, it's required to work even if you pass -1:
c
The int argument shall be converted to an unsigned char, and the
resulting byte shall be written.
This already works regardless of what we do just by assignment into a
char array.
However, for wide printf:
c
If no l (ell) qualifier is present, the int argument shall be
converted to a wide character as if by calling the btowc()
function and the resulting wide character shall be written.
There's no specification of what happens if btowc fails here, but
passing EOF to btowc is required to fail and return WEOF. It can also
fail depending on locale.
Rich
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