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  1. Qt
  2. QTBUG-81218

Fix nullptr-with-nonzero-offset in ucstrncmp().

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    Details

    • Commits:
      64359ad710756e7cca5ca553521b2aada18fb0fe (qt/qtbase/5.14) 5839535c9fb5d511ed8eec9250ac7ec52fe4e1f6 (qt/qtbase/5.12)

      Description

      The following fix is needed to allow forĀ 

      QString() == QString("")

      to pass using ubsan

           };
       
           // we're going to read a[0..15] and b[0..15] (32 bytes)
      -    for ( ; a + offset + 16 <= end; offset += 16) {
      +    for ( ; offset + 16 <= end - a; offset += 16) {
       #ifdef __AVX2__
               __m256i a_data = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(a + offset));
               __m256i b_data = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(b + offset));
      @@ -938,7 +938,7 @@ static int ucstrncmp(const QChar *a, const QChar *b, size_t l)
           }
       
           // we're going to read a[0..7] and b[0..7] (16 bytes)
      -    if (a + offset + 8 <= end) {
      +    if (offset + 8 <= end - a) {
               __m128i a_data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(a + offset));
               __m128i b_data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(b + offset));
               if (isDifferent(a_data, b_data))
      @@ -948,7 +948,7 @@ static int ucstrncmp(const QChar *a, const QChar *b, size_t l)
           }
       
           // we're going to read a[0..3] and b[0..3] (8 bytes)
      -    if (a + offset + 4 <= end) {
      +    if (offset + 4 <= end - a) {
               __m128i a_data = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(a + offset));
               __m128i b_data = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(b + offset));
               if (isDifferent(a_data, b_data))
      @@ -969,7 +969,7 @@ static int ucstrncmp(const QChar *a, const QChar *b, size_t l)
           if (l >= 8) {
               const QChar *end = a + l;
               const uint16x8_t mask = { 1, 1 << 1, 1 << 2, 1 << 3, 1 << 4, 1 << 5, 1 << 6, 1 << 7 };
      -        while (a + 7 < end) {
      +        while (7 < end - a) {
                   uint16x8_t da = vld1q_u16(reinterpret_cast<const uint16_t *>(a));
                   uint16x8_t db = vld1q_u16(reinterpret_cast<const uint16_t *>(b));
      
      

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            Assignee:
            thiago Thiago Macieira
            Reporter:
            cwgthornton Chris Thornton
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              Dates

              Created:
              Updated:
              Resolved:

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