Messages in this thread | | | From | Dmitry Torokhov <> | Subject | Re: typedefs and structs | Date | Tue, 8 Nov 2005 21:14:51 -0500 |
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On Tuesday 08 November 2005 19:59, Douglas McNaught wrote: > linas <linas@austin.ibm.com> writes: > > > On Tue, Nov 08, 2005 at 07:37:20PM -0500, Douglas McNaught was heard to remark: > >> > >> Yeah, but if you're trying to read that code, you have to go look up > >> the declaration to figure out whether it might affect 'foo' or not. > >> And if you get it wrong, you get silent data corruption. > > > > No, that is not what "pass by reference" means. You are thinking of > > "const", maybe, or "pass by value"; this is neither. The arg is not > > declared const, the subroutine can (and usually will) modify the contents > > of the structure, and so the caller will be holding a modified structure > > when the callee returns (just like it would if a pointer was passed). > > Right. My point is only that it's not clear from looking at the call > site whether a struct passed by reference will be modified by the > callee (some people pass by reference just for "efficiency"). And if > the called function modifies the data without the caller's knowledge, > it leads to obscure bugs. Whereas if you pass a pointer, it's > immediately clear that the called function can modify the pointed-to > object. >
A structure is almost never passed by value, no matter whether it is C or C++. So both languages require you either use descriptive naming or look up declaration/implementation:
C: struct str { char buf[1024]; int count; }; struct str s;
do_something_with_s(&s); do_something_else_with_s(&s);
Which one modufies s?
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