[1/3] : C++20 P0482R6 and C2X N2653: Fix for bug 25744, mbrtowc with Big5-HKSCS
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This patch for bug 25744 [1] updates the Big5-HKSCS converter to
properly maintain the lowest 3 bits of the mbstate_t __count data
member. This change is necessary to ensure that state is correctly
preserved when the converter encounters an incomplete multibyte
character. More details are available in bug 25744 [1].
The code changes are styled to match how these bits are maintained by
converters such as iso-2022-jp.c, ibm930.c, and others.
Running 'grep __count' in the 'iconvdata' directory suggests that a
number of other converters, euc-jisx0213.c for example, also fail to
preserve these bits in some cases, though it may be that negative
effects are not observed for those converters. This patch does not
attempt to address such issues with other converters.
Tested on Linux x86_64.
Tom.
[1]: Bug 25744
"mbrtowc with Big5-HKSCS returns 2 instead of 1 when consuming the
second byte of certain double byte characters"
https://sourceware.org/bugzilla/show_bug.cgi?id=25744
commit 9580fc4e7fa0ce33c049b0c2d61b98405fdd2ae3
Author: Tom Honermann <tom@honermann.net>
Date: Wed Jan 5 18:02:24 2022 -0500
Correct the Big5-HKSCS converter to preserve low order state bits.
BZ: https://sourceware.org/bugzilla/show_bug.cgi?id=25744
@@ -17769,7 +17769,7 @@ static struct
the output state to the initial state. This has to be done during the
flushing. */
#define EMIT_SHIFT_TO_INIT \
- if (data->__statep->__count != 0) \
+ if ((data->__statep->__count >> 3) != 0) \
{ \
if (FROM_DIRECTION) \
{ \
@@ -17778,7 +17778,7 @@ static struct
/* Write out the last character. */ \
*((uint32_t *) outbuf) = data->__statep->__count >> 3; \
outbuf += sizeof (uint32_t); \
- data->__statep->__count = 0; \
+ data->__statep->__count &= 7; \
} \
else \
/* We don't have enough room in the output buffer. */ \
@@ -17792,7 +17792,7 @@ static struct
uint32_t lasttwo = data->__statep->__count >> 3; \
*outbuf++ = (lasttwo >> 8) & 0xff; \
*outbuf++ = lasttwo & 0xff; \
- data->__statep->__count = 0; \
+ data->__statep->__count &= 7; \
} \
else \
/* We don't have enough room in the output buffer. */ \
@@ -17878,7 +17878,7 @@ static struct
\
/* Otherwise store only the first character now, and \
put the second one into the queue. */ \
- *statep = ch2 << 3; \
+ *statep = (ch2 << 3) | (*statep & 7); \
/* Tell the caller why we terminate the loop. */ \
result = __GCONV_FULL_OUTPUT; \
break; \
@@ -17895,7 +17895,7 @@ static struct
} \
else \
/* Clear the queue and proceed to output the saved character. */ \
- *statep = 0; \
+ *statep &= 7; \
\
put32 (outptr, ch); \
outptr += 4; \
@@ -17946,7 +17946,7 @@ static struct
} \
*outptr++ = (ch >> 8) & 0xff; \
*outptr++ = ch & 0xff; \
- *statep = 0; \
+ *statep &= 7; \
inptr += 4; \
continue; \
\
@@ -17959,7 +17959,7 @@ static struct
} \
*outptr++ = (lasttwo >> 8) & 0xff; \
*outptr++ = lasttwo & 0xff; \
- *statep = 0; \
+ *statep &= 7; \
continue; \
} \
\
@@ -17996,7 +17996,7 @@ static struct
/* Check for possible combining character. */ \
if (__glibc_unlikely (ch == 0xca || ch == 0xea)) \
{ \
- *statep = ((cp[0] << 8) | cp[1]) << 3; \
+ *statep = (((cp[0] << 8) | cp[1]) << 3) | (*statep & 7); \
inptr += 4; \
continue; \
} \
@@ -128,6 +128,71 @@ check_conversion (struct testdata test)
printf ("error: Result of third conversion was wrong.\n");
err++;
}
+
+ /* Now perform the same test as above consuming one byte at a time. */
+ mbs = test.input;
+ memset (&st, 0, sizeof (st));
+
+ /* Consume the first byte; expect an incomplete multibyte character. */
+ ret = mbrtowc (&wc, mbs, 1, &st);
+ if (ret != -2)
+ {
+ printf ("error: First byte conversion returned %zd.\n", ret);
+ err++;
+ }
+ /* Advance past the first consumed byte. */
+ mbs += 1;
+ /* Consume the second byte; expect the first wchar_t. */
+ ret = mbrtowc (&wc, mbs, 1, &st);
+ if (ret != 1)
+ {
+ printf ("error: Second byte conversion returned %zd.\n", ret);
+ err++;
+ }
+ /* Advance past the second consumed byte. */
+ mbs += 1;
+ if (wc != test.expected[0])
+ {
+ printf ("error: Result of first wchar_t conversion was wrong.\n");
+ err++;
+ }
+ /* Consume no bytes; expect the second wchar_t. */
+ ret = mbrtowc (&wc, mbs, 1, &st);
+ if (ret != 0)
+ {
+ printf ("error: First attempt of third byte conversion returned %zd.\n", ret);
+ err++;
+ }
+ /* Do not advance past the third byte. */
+ mbs += 0;
+ if (wc != test.expected[1])
+ {
+ printf ("error: Result of second wchar_t conversion was wrong.\n");
+ err++;
+ }
+ /* After the second wchar_t conversion, the converter should be in
+ the initial state since the two input BIG5-HKSCS bytes have been
+ consumed and the two wchar_t's have been output. */
+ if (mbsinit (&st) == 0)
+ {
+ printf ("error: Converter not in initial state.\n");
+ err++;
+ }
+ /* Consume the third byte; expect the third wchar_t. */
+ ret = mbrtowc (&wc, mbs, 1, &st);
+ if (ret != 1)
+ {
+ printf ("error: Third byte conversion returned %zd.\n", ret);
+ err++;
+ }
+ /* Advance past the third consumed byte. */
+ mbs += 1;
+ if (wc != test.expected[2])
+ {
+ printf ("error: Result of third wchar_t conversion was wrong.\n");
+ err++;
+ }
+
/* Return 0 if we saw no errors. */
return err;
}