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Avoid UBSan when negating the most negative sal_Int64 value

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...as exhibited by recently added 08e566f0c9 "add
a couple of tests for tools::BigInt"

Change-Id: Icd1080f86ccd985868fce34d6f86e2706acd58df
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/176677
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
Tested-by: Jenkins
This commit is contained in:
Stephan Bergmann 2024-11-16 16:20:29 +01:00
parent 2b8394b36b
commit 39f701d540
2 changed files with 8 additions and 5 deletions
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8
include/tools/bigint.hxx
View file

@ -164,10 +164,10 @@ inline BigInt::operator sal_Int64() const
case 1:
return bIsNeg ? -sal_Int64(nNum[0]) : nNum[0];
case 2:
if (sal_uInt64 n = (sal_uInt64(nNum[1]) << 32) + nNum[0]; bIsNeg && n <= maxForNegInt64)
return -sal_Int64(n); // maxForNegInt64 will convert correctly
else if (!bIsNeg && n <= maxForPosInt64)
return n;
if (sal_uInt64 n = (sal_uInt64(nNum[1]) << 32) + nNum[0]; bIsNeg && n < maxForNegInt64)
return -sal_Int64(n);
else if ((bIsNeg && n == maxForNegInt64) || (!bIsNeg && n <= maxForPosInt64))
return n; // maxForNegInt64 will convert correctly
}
assert(false && "out of range");
return 0;

5
tools/source/generic/bigint.cxx
View file

@ -25,6 +25,7 @@
#include <algorithm>
#include <cmath>
#include <cstring>
#include <limits>
#include <span>
/**
@ -461,7 +462,9 @@ BigInt::BigInt( sal_Int64 nValue )
}
else
{
for (sal_uInt64 n = static_cast<sal_uInt64>(bIsNeg ? -nValue : nValue); n != 0; n >>= 32)
for (sal_uInt64 n = static_cast<sal_uInt64>(
(bIsNeg && nValue != std::numeric_limits<sal_Int64>::min()) ? -nValue : nValue);
n != 0; n >>= 32)
nNum[nLen++] = static_cast<sal_uInt32>(n);
}
}