Re: PATCH: minor variable allocation change in add-zsh-hook

[Mikael Magnusson <mikachu@xxxxxxxxx>]

On Fri, Oct 2, 2015 at 11:44 PM, Matthew Hamilton <M@xxxxxxxxxxxxxx> wrote:
>
>
> On 10/02/2015 05:38 PM, Mikael Magnusson wrote:
>> On Fri, Oct 2, 2015 at 11:06 PM, Matthew Hamilton <M@xxxxxxxxxxxxxx> wrote:
>>> The 'local usage' variable is allocated in main, outside of the if loop
>>> that determines if it is going to print the usage information. This
>>> means time is spent allocating that variable, when in most cases, it
>>> will never be printed. It would be better to set it within the if loop,
>>> or alternatively, not using a variable and simply output the usage text
>>> as as literal string (as many other functions do).
>>>
>>> A trace of the time being needlessly being spent allocating the variable
>>> can be seen here: https://gist.github.com/Eriner/3192c9eb98fabdd70607
>>>
>>> It's not that much time, but it adds up and is inefficient/unnecessary.
>>>
>>> diff --git a/Functions/Misc/add-zsh-hook b/Functions/Misc/add-zsh-hook
>>> index ee37d67..bccd115 100644
>>> --- a/Functions/Misc/add-zsh-hook
>>> +++ b/Functions/Misc/add-zsh-hook
>>> @@ -19,7 +19,6 @@ hooktypes=(
>>>    chpwd precmd preexec periodic zshaddhistory zshexit
>>>    zsh_directory_name
>>>  )
>>> -local usage="Usage: $0 hook function\nValid hooks are:\n  $hooktypes"
>>>
>>>  local opt
>>>  local -a autoopts
>>> @@ -58,6 +57,7 @@ if (( list )); then
>>>    typeset -mp "(${1:-${(@j:|:)hooktypes}})_functions"
>>>    return $?
>>>  elif (( help || $# != 2 || ${hooktypes[(I)$1]} == 0 )); then
>>> +  local usage="Usage: $0 hook function\nValid hooks are:\n  $hooktypes"
>>>    print -u$(( 2 - help )) $usage
>>>    return $(( 1 - help ))
>>>  fi
>>
>> You would need to add tens of thousands of hooks before this would
>> make any difference, and then you're already far past the point of
>> sanity. I like the way the current code separates the content and
>> logic. There is also no such thing as an "if loop".
>>
>
> You're correct, I meant 'if statement'. My counter to that point would
> be to match how many of the other functions do it; they simply print the
> help and do not allocate any variables.
>
> ex: Functions/TCP/tcp_shoot
>
> if [[ $# -ne 2 ]]; then
>     print "Usage: tcp_dump host port

This one was a good example, because the usage message is actually
incorrect (tcp_dump instead of tcp_shoot) :).

> ex: Functions/VCS_Info/vcs_info_hookdel
>
> if (( ${#argv} < 2 )); then
>     print 'usage: vcs_info_hookdel [-a] <HOOK> <FUNCTION(s)...>'

Well, it's true that add-zsh-hook is the only function that does the
'local usage' thing, and I don't feel strongly about it. It just looks
nice to me the way it is in that particular case, what with the long
case statement coming before the print and all.

-- 
Mikael Magnusson