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Fix operator[] for vector2d and vector3d being potentially UB (#15977)

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We don't have a C++ expert on hand, but taking a pointer to one member
and expecting to access another by an offset is very fishy:
- for one, there could theoretically be padding
- the compiler might assume that we are only writing to that first member

The new code has shown to be free for constant parameter values.
Non-constant ones cause the assembly to have branches (why?), but we don't
use that much.
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sfan5 2025-04-08 22:25:45 +02:00 • committed by GitHub
parent 46db688cc8
commit a00b9cab36
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5 changed files with 39 additions and 30 deletions
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16
irr/include/vector2d.h
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@ -131,16 +131,20 @@ public:
T &operator[](u32 index)
{
_IRR_DEBUG_BREAK_IF(index > 1) // access violation
return *(&X + index);
switch (index) {
case 0: return X;
case 1: return Y;
default: IRR_CODE_UNREACHABLE();
}
}
const T &operator[](u32 index) const
{
_IRR_DEBUG_BREAK_IF(index > 1) // access violation
return *(&X + index);
switch (index) {
case 0: return X;
case 1: return Y;
default: IRR_CODE_UNREACHABLE();
}
}
//! sort in order X, Y.