冗長な記述とエラーとの相関とか
Using redundancies to find errors
邪悪なpdfはこちら→
http://www.stanford.edu/~engler/tse-redundant.pdf
Abstract.
Programmers generally attempt to perform useful work. If they performed an action, it was because they believed
it served some purpose. Redundant operations violate this belief. However, in the past redundant operations
have been typically regarded as minor cosmetic problems rather than serious errors. This paper demonstrates
that in fact many redundancies are as serious as traditional hard errors (such as race conditions or null
pointer dereferences). We experimentally test this idea by writing and applying five redundancy checkers to a
number of large open source projects, finding many errors. We then show that even when redundancies are
harmless they strongly correlate with the presence of traditional hard errors. Finally we show how flagging
redundant operations gives a way to detect mistakes and omissions in specifications. For example, a locking
specification that binds shared variables to their protecting locks can use redundancies to detect missing
bindings by flagging critical sections that include no shared state.
んで、例としてあげられていたのはたとえばこういうもの
/* linux2.4.1/net/atm/lec.c:lec addr delete: */
for(entry=priv->lec arp tables[i];
entry != NULL;
entry=next) } /* BUG: never reached */
next = entry->next;
if (...) {
lec_arp_remove(priv->lec_arp_tables, entry);
kfree(entry);
}
lec_arp_unlock(priv);
return 0;
}
/* linux2.4.5-ac8/fs/ntfs/unistr.c:ntfs collate names */
for (cnt = 0; cnt < min(name1_len, name2_len); ++cnt) {
c1 = le16_to_cpu(*name1++);
c2 = le16_to_cpu(*name2++);
if (ic) {
if (c1 < upcase len)
c1 = le16_to_cpu(upcase[c1]);
if (c2 < upcase len)
c2 = le16_to_cpu(upcase[c2]);
}
/* [META] stray terminator! */
if (c1 < 64 && legal_ansi_char_array[c1] & 8);
return err val;
if (c1 < c2)
return -1;
/* linux2.4.1/net/ipv6/raw.c:rawv6 getsockopt */
switch (optname) {
case IPV6 CHECKSUM:
if (opt->checksum == 0)
val = -1;
else
val = opt->offset;
/* BUG: always falls through */
default:
return -ENOPROTOOPT;
}
len=min(sizeof(int),len);
/* linux2.4.5-ac8/drivers/net/wan/sbni.c:sbni ioctl */
slave = dev get by name(tmpstr);
if(!(slave && slave->flags & IFF UP &&
dev->flags & IFF UP))
{
.../* print some error message, back out */
return ..EINVAL;
}
if (slave) { ... }
/* BUG: !slave is impossible */
else {
... /* print some error message */
return ..ENOENT;
}
/* linux2.4.5-ac8/drivers/scsi/qla1280.c:
qla1280 putq t */
srb_p = q->q_first;
while (srb_p)
srb_p = srb p->s_next;
if (srb_p) { /* BUG: this branch is never taken*/
sp->s prev = srb_p->s_prev;
if (srb_p->s_prev)
srb_p->s prev->s_next = sp;
else
q->q_first = sp;
srb_p->s_prev = sp;
sp->s next = srb_p;
} else {
sp->s_prev = q->q_last;
q->q_last->s_next = sp;
q->q_last = sp;
}
X. CONCLUSION
This paper explored the hypothesis that redundancies,
like type errors, flag higher-level correctness mistakes. We
evaluated the approach using five checkers which we applied to
the Linux, OpenBSD, and PostgreSQL. These simple analyses
found many surprising (to us) error types. Further, they correlated
well with known hard errors: redundancies seemed to flag
confused or poor programmers who were prone to other errors.
These indicators could be used to identify low-quality code
in otherwise high-quality systems and help managers choose
audit candidates in large code bases.
さよならソルシエ 2 (フラワーコミックスアルファ)
を読んだ。
とても良くできている作品だと思ったのだけど、
Amazonの書評で辛めの点をつけた人の気持ちもちょっとは分からないでもない気がした。
読解力云々をおいたとしても、
実在していた人間を扱ってあのように話を組み立てたという点を
感情的に受け入れがたい人は(割合はわからないけれども)一定数いるんじゃないかなあ。
まあそういうこというと歴史的な事柄、人物を扱った作品なんて書けなくなってしまうわけですが。
ヴィンランド・サガ(14) (アフタヌーンKC)
なんてのが最近出てまして、これは
フス戦争 - Wikipedia
というかなりマイナーな舞台なんじゃないかと
(Ruby コミッターには詳しい人も多そうな気がするけど…w)。
歴史物は好きだし、かわいい女の子が出てくるのもまあ。
といいつつそれを(戦争物というくくりで)混ぜるのはどうなのよ
という気がががが。
とか思ってたらこういう情報を発見
![パラダイム [DVD]](http://ecx.images-amazon.com/images/I/21X14DFVFVL._SL160_.jpg)
