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Fix 24855 - VRP fails to prevent overflow after division #17060

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Nov 13, 2024
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Fix 24855 - VRP fails to prevent overflow after division #17060

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7 changes: 6 additions & 1 deletion compiler/src/dmd/intrange.d
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Original file line number Diff line number Diff line change
Expand Up @@ -667,7 +667,7 @@ struct IntRange
return widest();

// Don't treat the whole range as divide by 0 if only one end of a range is 0.
// Issue 15289
// https://issues.dlang.org/show_bug.cgi?id=15289
if (rhs.imax.value == 0)
{
rhs.imax.value--;
Expand All @@ -681,6 +681,11 @@ struct IntRange
{
return IntRange(imin / rhs.imax, imax / rhs.imin);
}
else if (rhs.imin.negative && !rhs.imax.negative) // divisor spans [-1, 0, 1]
{
SignExtendedNumber[4] bdy = [-imin, imin, -imax, imax];
return IntRange.fromNumbers4(bdy.ptr);
}
else
{
// [a,b] / [c,d] = [min (a/c, a/d, b/c, b/d), max (a/c, a/d, b/c, b/d)]
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5 changes: 5 additions & 0 deletions compiler/test/compilable/testVRP.d
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Expand Up @@ -4,6 +4,7 @@
// https://issues.dlang.org/show_bug.cgi?id=3147
// https://issues.dlang.org/show_bug.cgi?id=6000
// https://issues.dlang.org/show_bug.cgi?id=5225
// https://issues.dlang.org/show_bug.cgi?id=24855

void add()
{
Expand Down Expand Up @@ -100,6 +101,10 @@ void divideFail()
short w;
byte y;
static assert(!__traits(compiles, y = w / -1));
static assert(!__traits(compiles, y = y / w));

short z;
static assert(!__traits(compiles, z = w / z + 1));
}

void plus1Fail()
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2 changes: 1 addition & 1 deletion druntime/src/core/internal/gc/impl/conservative/gc.d
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Expand Up @@ -1426,7 +1426,7 @@ short[PAGESIZE / 16][Bins.B_NUMSMALL + 1] calcBinBase()

foreach (i, size; binsize)
{
short end = (PAGESIZE / size) * size;
short end = cast(short) ((PAGESIZE / size) * size);
short bsz = size / 16;
foreach (off; 0..PAGESIZE/16)
{
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