C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  static allocation          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message sks_cpp Guest Posted: Wed Jul 30, 2003 4:23 am    Post subject: static allocation When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? Back to top John Harrison Guest Posted: Wed Jul 30, 2003 4:33 am    Post subject: Re: static allocation "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote Quote: When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. john Back to top Josephine Schafer Guest Posted: Wed Jul 30, 2003 4:49 am    Post subject: Re: static allocation "John Harrison" <john_andronicus (AT) hotmail (DOT) com> wrote Quote: "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote in message news:hLHVa.105778$R92.24264 (AT) news2 (DOT) central.cox.net... When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. Static variables in a function are constructed and destroyed only on the first invocation of the function. If the function never gets called the object is never created. Ofcourse this means an extra overhead to check if the object needs to be created each time the function is invoked. But don't pay for things you don't use. -- With best wishes, J.Schafer Back to top Josephine Schafer Guest Posted: Wed Jul 30, 2003 5:00 am    Post subject: Re: static allocation Quote: Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? Static variables are not allocated on the heap. Yes they have a region of their own. Back to top John Harrison Guest Posted: Wed Jul 30, 2003 5:04 am    Post subject: Re: static allocation "Josephine Schafer" <jsf (AT) usa (DOT) net> wrote Quote: "John Harrison" <john_andronicus (AT) hotmail (DOT) com> wrote in message news:bg7hqi$lhg80$1 (AT) ID-196037 (DOT) news.uni-berlin.de... "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote in message news:hLHVa.105778$R92.24264 (AT) news2 (DOT) central.cox.net... When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. Static variables in a function are constructed and destroyed only on the first invocation of the function. If the function never gets called the object is never created. Ofcourse this means an extra overhead to check if the object needs to be created each time the function is invoked. But don't pay for things you don't use. The question wsn't about construction, it was about memory allocation. john Back to top Josephine Schafer Guest Posted: Wed Jul 30, 2003 8:52 am    Post subject: Re: static allocation "John Harrison" <john_andronicus (AT) hotmail (DOT) com> wrote Quote: "Josephine Schafer" <jsf (AT) usa (DOT) net> wrote in message news:bg7ip6$l0hte$1 (AT) ID-192448 (DOT) news.uni-berlin.de... "John Harrison" <john_andronicus (AT) hotmail (DOT) com> wrote in message news:bg7hqi$lhg80$1 (AT) ID-196037 (DOT) news.uni-berlin.de... "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote in message news:hLHVa.105778$R92.24264 (AT) news2 (DOT) central.cox.net... When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. Static variables in a function are constructed and destroyed only on the first invocation of the function. If the function never gets called the object is never created. Ofcourse this means an extra overhead to check if the object needs to be created each time the function is invoked. But don't pay for things you don't use. The question wsn't about construction, it was about memory allocation. See static objects in a class are always constructed and destructed, no matter whether they are ever used or not. The same is not true for static variables in a function. So shouldn't the implementation defer the memory allocation also for such variables till their first invocation just like construction? Else we have paid a little even without having used it . Back to top Greg Comeau Guest Posted: Wed Jul 30, 2003 12:34 pm    Post subject: Re: static allocation In article <bg7je1$loq11$1 (AT) ID-192448 (DOT) news.uni-berlin.de>, Josephine Schafer <jsf (AT) usa (DOT) net> wrote: Quote: Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? Static variables are not allocated on the heap. Yes they have a region of their own. Just a side comment here that the standard never discusses things such as the stack, etc. So these are normally implementation things, though most implementation tend to use the same stragegy (optimization issues aside). -- Greg Comeau/ 4.3.0.1: FULL CORE LANGUAGE, INCLUDING TC1 Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90. Comeau C/C++ with Dinkumware's Libraries... Have you tried it? Back to top Greg Comeau Guest Posted: Wed Jul 30, 2003 12:42 pm    Post subject: Re: static allocation In article <bg7hqi$lhg80$1 (AT) ID-196037 (DOT) news.uni-berlin.de>, John Harrison <john_andronicus (AT) hotmail (DOT) com> wrote: Quote: "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote in message news:hLHVa.105778$R92.24264 (AT) news2 (DOT) central.cox.net... When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. Well, many compilers do it that way for namespace'd statics at least. Of course too, this does not necessarily apply to static members and probably some other situations too. -- Greg Comeau/ 4.3.0.1: FULL CORE LANGUAGE, INCLUDING TC1 Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90. Comeau C/C++ with Dinkumware's Libraries... Have you tried it? Back to top Greg Comeau Guest Posted: Wed Jul 30, 2003 12:47 pm    Post subject: Re: static allocation In article <bg7ip6$l0hte$1 (AT) ID-192448 (DOT) news.uni-berlin.de>, Josephine Schafer <jsf (AT) usa (DOT) net> wrote: Quote: "John Harrison" <john_andronicus (AT) hotmail (DOT) com> wrote in message news:bg7hqi$lhg80$1 (AT) ID-196037 (DOT) news.uni-berlin.de... "sks_cpp" <sksjava (AT) hotmail (DOT) com> wrote in message news:hLHVa.105778$R92.24264 (AT) news2 (DOT) central.cox.net... When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? All static variables, of all types, have their memory allocated at load time. Static variables in a function are constructed and destroyed only on the first invocation of the function. No, this too is just one of many possibilities. For instance, it may be done elsewhere. Or, it may be repeated if "EH failed". Quote: If the function never gets called the object is never created. Perhaps. Quote: Ofcourse this means an extra overhead to check if the object needs to be created each time the function is invoked. But don't pay for things you don't use. In a traditional implementation. -- Greg Comeau/ 4.3.0.1: FULL CORE LANGUAGE, INCLUDING TC1 Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90. Comeau C/C++ with Dinkumware's Libraries... Have you tried it? Back to top Greg Comeau Guest Posted: Wed Jul 30, 2003 1:02 pm    Post subject: Re: static allocation In article <bg8110$ktb28$1 (AT) ID-192448 (DOT) news.uni-berlin.de>, Josephine Schafer <jsf (AT) usa (DOT) net> wrote: Quote: See static objects in a class are always constructed and destructed, no matter whether they are ever used or not. But that's different. (actually, technically, that can be optimized away too in many cases) Quote: The same is not true for static variables in a function. So shouldn't the implementation defer the memory allocation also for such variables till their first invocation just like construction? The implementation has that freedom. -- Greg Comeau/ 4.3.0.1: FULL CORE LANGUAGE, INCLUDING TC1 Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90. Comeau C/C++ with Dinkumware's Libraries... Have you tried it? Back to top cody Guest Posted: Sun Sep 28, 2003 10:08 pm    Post subject: Re: static allocation Quote: When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? statics are like global variables but reside in a class. they are already contructed when the app starts and destroyed when the app ends so allocation and deallocation of them is nothing you have to worry about. they reside in their own memory location, where exactly this is is depends on the specific implementation but that does not matter for programming. -- cody [Freeware, Games and Humor] www.deutronium.de.vu || www.deutronium.tk Back to top Gianni Mariani Guest Posted: Sun Sep 28, 2003 11:19 pm    Post subject: Re: static allocation cody wrote: Quote: When do static members allocate memory? (at load time) How about static variables within a method? Where is the memory for static variables - is it allocated on the heap or does it have a region of its own? statics are like global variables but reside in a class. I think the OP asked for a static method variable. static method variables are initialized the first time the statment where is is defined is called and are destroyed upon program termination. The code below shows how it all works. #include <iostream> struct foo { const char * str; foo( const char * i_str ) : str( i_str ) { std::cout << "making foo" << str << "n"; } ~foo() { std::cout << "deleting foo" << str << "n"; } void useme() { std::cout << "using foo" << str << "n"; } }; struct zoo { void method( int v = 0 ) { static foo static_method_variable( "First" ); static_method_variable.useme(); if ( v == 0 ) { static foo static_method_variable( "Second" ); static_method_variable.useme(); } else if ( v == 1 ) { static foo static_method_variable( "Third" ); static_method_variable.useme(); } else if ( v == 2 ) { static foo static_method_variable( "Fourth" ); static_method_variable.useme(); } } }; int main() { std::cout << "in main n"; zoo zoo_obj1; zoo zoo_obj2; zoo_obj1.method( 1 ); zoo_obj2.method( 1 ); zoo_obj1.method( 0 ); zoo_obj2.method( 0 ); std::cout << "leaving main n"; } ---- produces ---- in main making fooFirst using fooFirst making fooThird using fooThird using fooFirst using fooThird using fooFirst making fooSecond using fooSecond using fooFirst using fooSecond leaving main deleting fooSecond deleting fooThird deleting fooFirst they are already Quote: contructed when the app starts .... they are initialized when the code containing the statment is first passed. and destroyed when the app ends so allocation Quote: and deallocation of them is nothing you have to worry about. they reside in their own memory location, where exactly this is is depends on the specific implementation but that does not matter for programming. 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