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Fix bug in mb_get_substr_slow (sometimes outputs wrong number of characters) #12983

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Merged
merged 1 commit into from
Dec 21, 2023
Merged

Fix bug in mb_get_substr_slow (sometimes outputs wrong number of characters) #12983

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5 changes: 3 additions & 2 deletions ext/mbstring/mbstring.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2092,9 +2092,10 @@ static zend_string* mb_get_substr_slow(unsigned char *in, size_t in_len, size_t
if (from >= out_len) {
from -= out_len;
} else {
enc->from_wchar(wchar_buf + from, MIN(out_len - from, len), &buf, !in_len || out_len >= len);
size_t needed_codepoints = MIN(out_len - from, len);
enc->from_wchar(wchar_buf + from, needed_codepoints, &buf, !in_len || out_len >= len);
from = 0;
len -= MIN(out_len, len);
len -= needed_codepoints;
}
}

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6 changes: 6 additions & 0 deletions ext/mbstring/tests/mb_substr.phpt
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Expand Up @@ -133,6 +133,11 @@ echo "Regression:\n";
$str = "\xbd\xbd\xbd\xbd\xbd\xbd\xbd\xbe\xbd\xbd\xbd\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x89\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x00\x00\x00\x00\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8b\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8f\x8b\x8b\x8b\xbd\xbd\xbd\xbd\xbd\xbd\xbd\xbe\x01:O\xaa\xd3";
echo bin2hex(mb_substr($str, 0, 128, "JIS")), "\n";

/* Alex messed up when reimplementing mb_substr and, in cases where `from` is non-zero and
* the number of characters to extract is more than 128, miscalculated where to end the substring
* Thanks to Maurício Fauth for finding the issue */
var_dump(mb_substr('Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum dapibus feugiat ex non cursus. Pellentesque vestibulum tellus sit lectus.', 19, -1));
Comment on lines +136 to +139
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Why not make this a separate test file altogether?

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@kamil-tekiela Thanks for the suggestion. Personally I prefer to have this particular test here rather than multiplying the number of different test files, but certainly some might prefer to have each test case in a different file. In any case, I do appreciate your bringing out this suggestion.


?>
--EXPECT--
EUC-JP:
Expand Down Expand Up @@ -213,3 +218,4 @@ Testing agreement with mb_strpos on invalid UTF-8 string:
?AAA
Regression:
1b28493d3d3d3d3d3d3d3e3d3d3d1b28423f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f000000003f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f3f1b28493d3d3d3d3d3d3d3e1b2842013a4f1b28492a1b2842
string(121) "it amet, consectetur adipiscing elit. Vestibulum dapibus feugiat ex non cursus. Pellentesque vestibulum tellus sit lectus"