leo@atcmp.nl (Leo Willems) (06/08/90)
Since C++ 2.0 assignment to this is an anachronism. Is it still ok to check the this pointer against 0 to figure out if an object is on the heap or not? I need to know this, despite the fact that I can define my own class::operator new(), currently I'm using an ugly workaround. If so, will this be the case in next releases? If so, is there still the "all possible execution paths" catch? Thanks, (I couldn't find it in the 2.0 syntax reference) Leo Willems Internet: leo@atcmp.nl AT Computing UUCP: mcsun!hp4nl!kunivv1!atcmpe!leo P. O. Box 1428 6501 BK Nijmegen Phone: +31-80-566880 The Netherlands Fax: +31-80-555887
pkturner@cup.portal.com (Prescott K Turner) (06/13/90)
leo@atcmp.nl (Leo Willems) writes: > Is it still ok to check the this pointer against 0 to figure out if > an object is on the heap or not? Cfront 2.0 and Turbo C++ still support assignment to 'this'. But what you have in mind, i.e. to test 'this' against 0 in a constructor without assigning to 'this', never worked. -- Prescott K. Turner, Jr. Language Processors, Inc. 959 Concord St., Framingham, MA 01701 USA (508) 626-0006 x232 UUCP: ...sun!cup.portal.com!pkturner Internet: pkturner@cup.portal.com
leo@atcmp.nl (Leo Willems) (06/14/90)
From article <30734@cup.portal.com>, by pkturner@cup.portal.com (Prescott K Turner): > leo@atcmp.nl (Leo Willems) writes: > >> Is it still ok to check the this pointer against 0 to figure out if >> an object is on the heap or not? > > Cfront 2.0 and Turbo C++ still support assignment to 'this'. > But what you have in mind, i.e. to test 'this' against 0 in a constructor > without assigning to 'this', never worked. > -- No, what I had in mind was checking <this> (and having to assign to <this>, to make the check work) against 0 to decide if my object is made trough new (or not). The penalty for the check was that I had to malloc()/free() myself. The reason I posted this question was, to be more precise: How to find out if an object is created through new, or is an auto or static (global)? This check must be done in the class its constructor. (restriction: I cannot redefine new for the class.) Up to now nobody gave me a clue to solve that. Leo
thomasw@hpcupt1.HP.COM (Thomas Wang) (06/14/90)
/ hpcupt1:comp.lang.c++ / pkturner@cup.portal.com (Prescott K Turner) / 9:20 pm Jun 12, 1990 / >leo@atcmp.nl (Leo Willems) writes: >> Is it still ok to check the this pointer against 0 to figure out if >> an object is on the heap or not? >Cfront 2.0 and Turbo C++ still support assignment to 'this'. >But what you have in mind, i.e. to test 'this' against 0 in a constructor >without assigning to 'this', never worked. This is what I use currently, until a better way appears. // explain function // Is this object allocated from the stack? // This code is machine dependent. It assumes stack have a higher address // than heap space. char base_ref_t::is_stack_object() { char x; return ((unsigned int) this) > ((unsigned int) &x); } >Prescott K. Turner, Jr. >UUCP: ...sun!cup.portal.com!pkturner Internet: pkturner@cup.portal.com