What to do after Python?

Erno Kuusela erno-news at erno.iki.fi
Mon Feb 19 00:02:50 EST 2001

In article <roy-770A13.20533818022001 at news.panix.com>, Roy Smith
<roy at panix.com> writes:

| Erno Kuusela <erno-news at erno.iki.fi> wrote:
|| |    if (length = strlen(s))
|| |       s[length-1] = 0;
|| | and cut your instruction count in half :-)
|| a sensible optimising compiler will generate identical code for both.

| I will admit that my compiler theory is a bit rusty, but it's hard to see 
| how a compiler would know that the strlen function would return the same 
| value when called again with the same argument (idempotent?).

it's part of the language, so the compiler is allowed to have
special knowledge about it.

| In any case, I just tried it on my Linux box (GNU compiler) and on a 
| Solaris machine (Sun Workshop compiler).  Neither compiler generated the 
| same code for the two versions, regardless of whether optimizing was turned 
| on or not.  Both generated two strlen stanzas (see below), with or without 
| -O.

i guess they are not sensible then ;)

at least the cc/libc combo on linux does have special knowledge about
many functions, including strlen, but i guess this case has not been
considered important enough to bother with.

look in /usr/include/bits/string.h on your linux box and
at <URL:http://puffin.external.hp.com/lxr/

  -- erno

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