Commit 5b630501 authored by Noah Misch's avatar Noah Misch

Skip memcpy(x, x) in qunique().

It has undefined behavior.  Follow the precedent of commit
9a9473f3.  No back-patch, since the
master branch alone has this function.

Discussion: https://postgr.es/m/20191229070221.GA13873@gust.leadboat.com
parent fac1c04f
......@@ -30,8 +30,9 @@ qunique(void *array, size_t elements, size_t width,
for (i = 1, j = 0; i < elements; ++i)
{
if (compare(bytes + i * width, bytes + j * width) != 0)
memcpy(bytes + ++j * width, bytes + i * width, width);
if (compare(bytes + i * width, bytes + j * width) != 0 &&
++j != i)
memcpy(bytes + j * width, bytes + i * width, width);
}
return j + 1;
......@@ -55,8 +56,9 @@ qunique_arg(void *array, size_t elements, size_t width,
for (i = 1, j = 0; i < elements; ++i)
{
if (compare(bytes + i * width, bytes + j * width, arg) != 0)
memcpy(bytes + ++j * width, bytes + i * width, width);
if (compare(bytes + i * width, bytes + j * width, arg) != 0 &&
++j != i)
memcpy(bytes + j * width, bytes + i * width, width);
}
return j + 1;
......
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