delphi - Does the compiler optimize (close) identical FieldByName calls? -


in code i'm maintaining, see 2 different methods used in tclientdataset.oncalcfields event handlers:

 dataset  begin    // 1. call fieldbyname twice    if amindate > fieldbyname(splanallocatiefromdate).asdatetime       amindate := fieldbyname(splanallocatiefromdate).asdatetime;    // 2. put retrieved fieldbyname value in temp var    lempid := fieldbyname(splanallocatieempid).asinteger;    if lempid <> 0 ltsallocatedempids.add(inttostr(lempid));  end;

will compiler (delphi xe2, win32 app) optimize method 2 use temp var? 2 fieldbynames quite close, nested.

if not, should rewrite 1. because oncalcfields executes often.

btw. know fields[] versus fieldbyname(), or using temp tfield var when running eof loop, not issue here.

no version of delphi compiler this.

such optimizations require compiler able prove 2 calls fieldbyname give same result, , there no provision flagging method being deterministic.

note quite possible in theory (if unlikely in reality) 2 calls not give same result, in case e.g. if different thread deletes field out of collection between first , second call. generally, compiler not know or care @ call site particular method call does.


Comments

Post a Comment

Popular posts from this blog

javascript - RequestAnimationFrame not working when exiting fullscreen switching space on Safari -

request animation frame stops working when exiting fullscreen clicking on original space's safari window. fine if fullscreen mode canceled escape key or calling cancelfullscreen(). steps reproduce: open https://dl.dropboxusercontent.com/u/769042/prezi/safari-fullscreen.html click "draw raf", kittie appears click "fullscreen", go fullscreen click "draw raf", kittie appears go space original safari was, showing "click exit fullscreen mode", click anywhere, out fullscreen click "draw raf", nothing happens what handling click calling: window.requestanimationframe(draw); which draws on canvas context: function draw() { ctx.drawimage(img, math.random()*500|0, math.random()*400|0, 100, 100); } i checked .hidden , .visibilitystate, updated correctly. tested on osx 10.9.3, safari 7.0.4 (9537.76.4). has workaround/solution other switching old settimeout? this sounds webkit bug 88940 : using reque
Read more

Python ctypes access violation with const pointer arguments -

i have api i'm trying wrap in python (2.7.6 on win7) code using ctypes. here's api: client_dllfunc bool clientapi search_exporttoclipcopy(clienthsearch handle, int channel, lpctstr filename, const time_t& from, const time_t& to, const bool* cameras, int length, bool usepassword, lpctstr password, bool includetextin = false, bool excludeplayer = false); the issue i'm having cameras argument; , i've had issue other const pointer arguments well. here's how i'm wrapping api: def search_exporttoclipcopy(self, hsearch, csearch, filename, tfrom, tto, cameras, length, usepassword, password, includetextin=true, excludeplayer=false): exporttoclipcopy = self.sdkdll.search_exporttoclipcopy exporttoclipcopy.argtypes = [c_int, c_int, c_wchar_p, c_long, c_long, pointer(c_bool), c_int, c_bool, c_wchar_p, c_bool, c_bool] exporttoclipcopy.restype = c_bool exporttoclipcopy(hsearch, csearch, filename, tfrom, tto, cameras, length, usepassword, pass
Read more