BUG #6700: Potential Bug in numeric.c

The following bug has been logged on the website:

Bug reference: 6700
Logged by: Ken Cheung
Email address: msrbugzilla(at)gmail(dot)com
PostgreSQL version: Unsupported/Unknown
Operating system: Linux
Description:

I observed a code clone in the following files. In the function
PGTYPESnumeric_copy, the variable dst is ensured to be not NULL before
passing to zero_var(). However, the function PGTYPESnumeric_from_decimal
does not perform this checking. It will cause an exception when dst is NULL
and passed to zero_var().

function : PGTYPESnumeric_copy @ (file:
"postgresql-9.2beta2/src/interfaces/ecpg/pgtypeslib/numeric.c", line:
1476)~1491
if (dst == NULL)
return -1;
zero_var(dst);

dst->weight = src->weight;
dst->rscale = src->rscale;
dst->dscale = src->dscale;
dst->sign = src->sign;

if (alloc_var(dst, src->ndigits) != 0)
return -1;

for (i = 0; i < src->ndigits; i++)
dst->digits[i] = src->digits[i];

return 0;

function : PGTYPESnumeric_from_decimal @ (file:
"postgresql-9.2beta2/src/interfaces/ecpg/pgtypeslib/numeric.c", line:
1650)~1663
zero_var(dst);

dst->weight = src->weight;
dst->rscale = src->rscale;
dst->dscale = src->dscale;
dst->sign = src->sign;

if (alloc_var(dst, src->ndigits) != 0)
return -1;

for (i = 0; i < src->ndigits; i++)
dst->digits[i] = src->digits[i];

return 0;