What to do after Python?
roy at panix.com
Mon Feb 19 02:53:38 CET 2001
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?).
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
The most interesting case was Linux with -O. I don't know i86 assembler,
so I'm guessing a bit here, but seems to have in-lined the strlen function,
eliminating the subroutine call completely. It still left what looks like
two code fragments to count the length of the string.
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