From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII X-Google-Thread: f849b,d275ffeffdf83655 X-Google-Attributes: gidf849b,public X-Google-Thread: f5d71,d275ffeffdf83655 X-Google-Attributes: gidf5d71,public X-Google-Thread: 146b77,d275ffeffdf83655 X-Google-Attributes: gid146b77,public X-Google-Thread: 109fba,d275ffeffdf83655 X-Google-Attributes: gid109fba,public X-Google-Thread: 1108a1,d275ffeffdf83655 X-Google-Attributes: gid1108a1,public X-Google-Thread: 115aec,d275ffeffdf83655 X-Google-Attributes: gid115aec,public X-Google-Thread: 101b33,d275ffeffdf83655 X-Google-Attributes: gid101b33,public X-Google-Thread: 103376,d275ffeffdf83655 X-Google-Attributes: gid103376,public From: James Kanze Subject: Re: Ada vs C++ vs Java Date: 1999/01/18 Message-ID: <36A35D67.412F4820@dresdner-bank.com>#1/1 X-Deja-AN: 434035915 Content-Transfer-Encoding: 8bit References: <369C1F31.AE5AF7EF@concentric.net> <369DDDC3.FDE09999@sea.ericsson.se> <369e309a.32671759@news.demon.co.uk> <369F0592.94F9DDDA@dresdner-bank.com> <77pnr4$ch3$1@newnews.global.net.uk> <36a3281a.11980677@news.demon.co.uk> X-Accept-Language: fr,en,de Content-Type: text/plain; charset=iso-8859-1 Organization: Dresdner Bank Mime-Version: 1.0 Newsgroups: comp.lang.ada,comp.lang.c++,comp.vxworks,comp.lang.java,comp.java.advocacy,comp.realtime,comp.arch.embedded,comp.object,comp.lang.java.programmer Date: 1999-01-18T00:00:00+00:00 List-Id: John Birch wrote: |> On Sun, 17 Jan 1999 06:53:08 GMT, Matthew Heaney |> wrote: |> >"John Birch" writes: |> > |> >> The reason IMHO is that C++ inherently relies upon dynamic memory |> >> allocation! It's really as simple as that. If you can show me how to |> >> calculate the maximum amount of memory required by a given C++ program then |> >> I'll reconsider, until then I'll continue using C without malloc and free! |> > |> >When does C++ "inherently rely upon dynamic memory allocation"? |> > |> OK, say I have the following; |> Complex one (1), Complex two (2), Complex three (3), Complex four (4); |> Complex Sum; |> Sum = one + two + three + four; |> If Complex is a class with an overloaded + operator, I get temporary |> objects generated (possibly at the compiler's option) in the above |> statement. Since it can be written as; |> Sum = operator + (operator + (operator +(one, two), three), four); |> Now where do these temporary objects get created? On the stack, or on |> the heap. On the stack. |> In C the stack size (without recursion) can never grow beyond the |> maximum of the total of the stack requirements of all of the functions |> defined. The rules concerning the growth of stack size are the same in both C and C++. In particular, change the name of the function in the above to addComplex, and there is really no difference in this case between C and C++. The expression: Sum = addComplex( addComplex( addComplex( one , two ) , three ) , four ) ; in C will require at least three instances of Complex as temporaries on the stack. |> How do I calculate the potential stack size in C++? Exactly like you do in C. |> There is inherent dynamic memory allocation going on here, it is |> irrelevant whether it is satck or heap. I (the coder) did not |> explicitly allocate memory, the language (or rather the implementation |> of the language) did. Which it does in any language. There are only a limited number of registers available -- on Intel architecture, a *very* limited number. Once the compiler has used all of these for its temporaries, it will spill to memory. Which it allocates on the stack. In addition, I know of no compiler in C or C++ which will try and keep a struct or class temporary in a register, even if it fits and none of the operations on it really require an address. -- James Kanze GABI Software, S�rl Conseils en informatique orient� objet -- -- Beratung in industrieller Datenverarbeitung mailto: kanze@gabi-soft.fr mailto: James.Kanze@dresdner-bank.com