Re: It's seems that the function "do_text_output_multiline" does not suit for format "line1\nline2\n...lineN".

David Rowley <david.rowley@2ndquadrant.com> writes:
> On 20 May 2016 at 19:13, Hao Lee <mixtrue@gmail.com> wrote:
>> Today, I am do some works on adding some customized featues to PostgreSQL 9.6 beta1. But, when i do some output to
psqlusing the fuction "do_text_output_multiline" with the string just like mentioned in mail tilte, such as "this is
a\ntestfor\nnew blank.". the PostgreSQL may lead to corruption in this function, and i debugged it that found this
functioncan not dealt with the boundaries properly. The original function code as :
 

> Thanks for reporting this. It does seem pretty broken. I guess we've
> only gotten away with this due to EXPLAIN output lines always having a
> \n at the end of them, but we should fix this.

Agreed.

> Your proposed fix looks a little bit confused. You could have just
> removed the eol += len; as testing if (eol) in the else will never be
> true as that else is only being hit because eol is NULL.

I think really the right fix is "eol = text + len" rather than modifying
the loop condition.  Almost certainly, that is what the original coder
intended, but typo'd the statement and nobody ever noticed.

> I shuffled things around in there a bit and came up with the attached fix.

I didn't like this version because it duplicated the string-conversion
code, which admittedly is only one line, but not a very simple line.
I pushed something based on "eol = text + len" instead.
        regards, tom lane