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Fix issue 19128 - argument to alloca may be too large #2409

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wilzbach merged 1 commit into from
Dec 18, 2018
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Fix issue 19128 - argument to alloca may be too large #2409

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25 changes: 13 additions & 12 deletions src/rt/arrayassign.d
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,12 @@ extern (C) void[] _d_arrayassign(TypeInfo ti, void[] from, void[] to)

// Need a temporary buffer tmp[] big enough to hold one element
void[16] buf = void;
void* ptmp = (elementSize > buf.sizeof) ? alloca(elementSize) : buf.ptr;
void* ptmp = (elementSize > buf.sizeof) ? malloc(elementSize) : buf.ptr;
scope (exit)
{
if (ptmp != buf.ptr)
free(ptmp);
}
return _d_arrayassign_l(ti, from, to, ptmp);
}

Expand Down Expand Up @@ -206,24 +211,20 @@ extern (C) void* _d_arraysetassign(void* p, void* value, int count, TypeInfo ti)

auto element_size = ti.tsize;

//Need a temporary buffer tmp[] big enough to hold one element
void[16] buf = void;
void[] tmp;
if (element_size > buf.sizeof)
{
tmp = alloca(element_size)[0 .. element_size];
}
else
tmp = buf[];
// Need a temporary buffer tmp[] big enough to hold one element
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@PetarKirov PetarKirov Dec 17, 2018

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Suggested change
// Need a temporary buffer tmp[] big enough to hold one element
// Need a temporary buffer big enough to hold one element.
// Stack allocate if element_size < 512.

immutable maxAllocaSize = 512;
void *ptmp = (element_size > maxAllocaSize) ? malloc(element_size) : alloca(element_size);

foreach (i; 0 .. count)
{
memcpy(tmp.ptr, p, element_size);
memcpy(ptmp, p, element_size);
memcpy(p, value, element_size);
ti.postblit(p);
ti.destroy(tmp.ptr);
ti.destroy(ptmp);
p += element_size;
}
if (element_size > maxAllocaSize)
free(ptmp);
return pstart;
}

Expand Down