RE: [Dev-C++] STL Map question

[Ioannis V. <iv...@em...>]

> -----Original Message-----
> From: dev...@li...=20
> [mailto:dev...@li...] On Behalf=20
> Of Shane Bryldt
> Sent: Monday, July 14, 2003 11:14 PM
> To: Hossein Haeri
> Cc: C++
> Subject: Re: [Dev-C++] STL Map question
>=20
> When it breaks out into GDB in the crash,=20
> it leaves me at
> a "map::find" statement, which, when I step into it, I find=20
> that the key (an
> std::string) is valid, but the data portion, a pointer to an=20
> allocated User,
> is somehow fubar'd, because if I try to print (no different=20
> than getting the
> value of a variable in VC++ debugger) the pointer, GDB itself=20
> will indicate
> that the program crashed while attempting to execute=20
> something by GDB.  This
> means that 1) the code crashes and drops me into the=20
> debugger, and 2) it is
> in fact crashing because of the variable value, as executing=20
> the single
> operation of printing the value causes an internal crash that=20
> GDB recovers
> from, but ends execution of the program.


This is happening because you use the library in an improper C style =
way.
Had the map contained objects instead of pointers you would find no =
record
when you used the find() and would get User(0) when accessed the key =
using
operator[]. Better use C++ as C++ and not as C.


Quiz of the day: How do you write generic functions in C and how in C++? =
:-)



=20
> The problem I am seeing, I have never seen in all my time=20
> programming, and I
> have a good 8 years background with C.  Further issues with=20
> this, may result
> in me reverting UserList to a true linked list=20
> implementation, instead of
> STL, which could be the culprit even though I don't want to=20
> blame it.=20


!!!  The problem is your programming approach, not the standard library!



> Even
> reverting temporarily to a C linked list may help me in=20
> travelling the list
> in the debugger to find out where the problem is (like if=20
> it's the last or
> first element, etc)...  Short of testing my new changes, this=20
> will be the
> next step, to revert to a very slow and simple linked list=20
> until I can track
> down the problem.  At least I have some direction, I=20
> appreciate the help
> everyone has offered.


The standard library provides a double linked list implementation,
std::list. But your problem is that you code in C with classes, not C++!






Ioannis Vranos
=20
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