c++ - Is an empty function called at all in optimised code? -


if test macro not defined, know whether there performance difference in these 2 pieces of code:

void func1(int a) {     ... }  #ifdef test func1(123); #endif

and:

void func2(int a) { #ifdef test     ... #endif }  func2(123);

with test not defined, func2 become , empty function complier should not call @ all, isn't it?

thank you.

it pretty comes down whether particular call func2 inlined or not. if is, optimizing compiler ought able make inlined call empty function same not calling @ all. if isn't inlined, it's called , returns immediately.

as long function definition available in tu containing call func2, there's no obvious reason won't inlined.

this relies on fact 123 literal, evaluating arguments of call has no side-effects. args have evaluated if function call has no effect, so:

int = 0;  /* 'i' incremented, if call optimized out */ func2(++i);  /* 'i' not incremented when 'test' undefined */ #ifdef test func1(++i); #endif

Comments

Post a Comment

Popular posts from this blog

c# - SharpSVN - How to get the previous revision? -

i trying find efficient way previous revision of file text comparison using sharpsvn. using (svnclient c = new svnclient()) { c.authentication.defaultcredentials = new networkcredential( configurationmanager.appsettings.get("svnserviceusername") , configurationmanager.appsettings.get("svnservicepassword") , configurationmanager.appsettings.get("svnservicedomain") ); c.authentication.sslservertrusthandlers += new eventhandler<svnsslservertrusteventargs>(authentication_sslservertrusthandlers); collection<svnfileversioneventargs> fileversioncollection = new collection<svnfileversioneventargs>(); svnrevisionrange range = new svnrevisionrange(0, this.hooks.revision); svnfileversionsargs args = new svnfileversionsargs(); args.retrieveproperties = true; args.range = range; foreach (svnchangeitem item in log.changedpaths) { string path = this.repositorypath + it...
Read more

c++ - Is it possible to compile a VST on linux? -

for class project i'm attempting write vst plugin backed cuda. current cuda workflow on linux box, i'd prefer compile , link there. according wikipedia , should possible (i couldn't find steinberg documentation relevant linux) can't find makefile or instructions on how build if aren't using xcode or visual studio. i'm vst 3 sdk doesn't support linux. when try compile plugin under linux, error: ./base/source/fatomic.cpp:39:30: fatal error: libkern/osatomic.h: no such file or directory this issue caused following code in "vst3 sdk/base/source/fatomic.cpp" #if mac #include <libkern/osatomic.h> #if mac_os_x_version_min_required > mac_os_x_version_10_4 #define native_atomic_type (volatile int32_t*) #else #define native_atomic_type (int32_t*) #endif #elif windows #include <windows.h> #endif but hope compiling under linux work vst sdk 2.4. reading. jvstwrapper seems run on lin...
Read more

url - Querystring manipulation of email Address in PHP -

i using third party application (email2http) send me emailid, body , message. unable retrieve email id due name appended on , enclosed < , >. here querystring getting. test.php?from=ajay+reddy &subject=cx&body=somebody when print variable in php returns name , not email id. $from = $_get['from']; echo $from; //output ajay reddy please suggest me how can emailid also. i dont want use post method due testing , debugging. it's working fine. forgot use htmlentities() in debugging.
Read more