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Avoid calling memcpy() with a NULL source pointer and count == 0.

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As in commit 0a52d378b03b7d5a, avoid doing something that has undefined
results according to the C standard, even though in practice there does
not seem to be any problem with it.

This fixes two places in numeric.c that demonstrably could call memcpy()
with such arguments.  I looked through that file and didn't see any other
places with similar hazards; this is not to claim that there are not such
places in other files.

Per report from Piotr Stefaniak.  Back-patch to 9.5 which is where the
previous commit was added.  We're more or less setting a precedent that
we will not worry about this type of issue in pre-9.5 branches unless
someone demonstrates a problem in the field.
This commit is contained in:
Tom Lane 2015-08-02 15:48:27 -04:00
parent cb3384a0cb
commit 13bba02271
1 changed files with 5 additions and 2 deletions
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7
src/backend/utils/adt/numeric.c
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@ -4769,7 +4769,9 @@ set_var_from_var(NumericVar *value, NumericVar *dest)
newbuf = digitbuf_alloc(value->ndigits + 1);
newbuf[0] = 0; /* spare digit for rounding */
memcpy(newbuf + 1, value->digits, value->ndigits * sizeof(NumericDigit));
if (value->ndigits > 0) /* else value->digits might be null */
memcpy(newbuf + 1, value->digits,
value->ndigits * sizeof(NumericDigit));
digitbuf_free(dest->buf);
@ -5090,8 +5092,9 @@ make_result(NumericVar *var)
result->choice.n_long.n_weight = weight;
}
memcpy(NUMERIC_DIGITS(result), digits, n * sizeof(NumericDigit));
Assert(NUMERIC_NDIGITS(result) == n);
if (n > 0)
memcpy(NUMERIC_DIGITS(result), digits, n * sizeof(NumericDigit));
/* Check for overflow of int16 fields */
if (NUMERIC_WEIGHT(result) != weight ||