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Re: Analysis of clang results for nmap main directory.
From: David Fifield <david () bamsoftware com>
Date: Thu, 14 Jun 2012 11:12:06 -0700

On Thu, Jun 14, 2012 at 02:03:32PM -0400, James Rogers wrote:
On Thu, Jun 14, 2012 at 1:42 PM, David Fifield <david () bamsoftware com> wrote:
On Thu, Jun 14, 2012 at 01:06:01PM -0400, James Rogers wrote:
Reran clang against latest version of nmap on Tuesday, many changes
had been made since I first ran this tool and I wanted the results to
be as meaningful as possible.

The rest of the bugs are just an assignment or increment of a local
variable and the variable never being used again after the last
change.  Not actual bugs, but good coding practices discourge setting
variable you never use again.

I have comments on a few of these.

Dead store    Dead assignment                                         output.cc               2160
2160  delim = "; ";
      Value stored to 'delim' is never read
      Bug, line can be removed with affecting program.

I don't think this line should be removed. Look at the preceding code:
it's part of a symmetric structure of similar code blocks. Imagine what
happens if another block is added at the end; the lack of an assignment
to delim would be a bug. This is sort of like defensively putting a
"break" after your last "switch" case; it is useless but it protects you
when you add another case. Maybe this whole section can be rewritten to
be clearer, but as it stands I think the assignment should remain.


Maybe the symmetry could be

delim="; ";
block of code

in the preceding sections.  If someone copies and pastes a block to
the end, then it would still work.

I don't think that's right. Did you try it? I think it would cause
output like

Service Info:; OS: Unix

instead of the expected

Service Info: OS: Unix

Dead store    Dead assignment                                         scan_engine.cc          5872
5872  res = recvtime(sd, recvbuf, 2048, 10, NULL);
      Value stored to 'res' is never read
      Is a Bug.  remove "res =" or do something with res.

These are the kinds of bugs we're looking for. You should handle this
case the same as other assignments to res in the same function.

The real problem is  "Should res be checked later and is not?"

It should be checked immediately after the recvtime, and is not. Look
elsewhere in the function; recvtime errors are already being handled;
this looks like a simple oversight.

Dead store    Dead assignment                                         traceroute.cc           1051
1051  hop = host->insert_hop(ttl, from_addr, rtt);
      Value stored to 'hop' is never read
      Bug.  Hop is calculated, but never added to chain.  Misleading braket spacing.

What is misleading about the spacing? I don't see it.

Returns without doing anything with the hop variable that was set.
The } following the else looks like part of the else, but it is part
of the if that follows the else.  The rest of the function is working
with hop.

If that is correct, then we shouldn't set the local hop variable there.

I think the indentation reflects the program flow exactly. The "else"
part of the branch is using the hop from hop_cache_lookup, not
host->insert_hop. You can remove the hop assignment in the "hop == NULL"
branch. Maybe the function originally returned hop or something, in
which case we would need the assignment there.

David Fifield
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