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Wait a minute... isn't that code example missing some indirection?
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Or maybe that's not C? Can you return a local variable like that in C? Even returning a pointer to a local variable is verboten isn't it?
Or is my C-fu still that rusty?
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sure, you can return locals - even if they're structs.
a pointer to a local would be a bad idea, because the local goes out of scope. but when you return a local, it makes a copy for the caller.
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Huh. I guess I thought C was dumber than that, one semester of C wasn't enough. That explains that small memory leak I wrote in 1994... I wonder whether or not that program is still in use... 
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I pulled out my old VAX C book for reference, and all I see is passing structs in as parameters, but it seems to say it's limited to 1020 bytes. If that's true, it must apply to return values as well -- they're still on the stack, yes?
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that's probably the VMS stack size.
i believe the struct returning behavior is compiler dependent (OS dependent?). some will return the struct in a register, if the struct is small enough, or on the stack. some compilers are smart enough to use the caller's struct directly so as to avoid making a copy.
that struct i showed is sizeof(int *) + sizeof(int). so, 8 or 12 bytes. nothing to worry about.
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I believe that's implementation defined. With my linux box I can use ulimit to set the size of the stack. By default it seems to be 8MB, but I can modify that upwards more or less as needed (obviously within memory limits of the system).
I seem to recall that early C implementations were limited to returning basic types (e.g. int, double, char *, etc). gcc-5.2 still has a warning flag for aggregate returns - which suggests that other C compilers might still adhere to that.
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Method 0 is the one I observe most of the time (and use myself more frequently). Even Windows API use it.
Sentinel method has its usages (k5054 already pointed out its drawbacks).
I won't use method 2, I mean I won't choose a linked list instead of an array just in order to avoid the extra parameter in my function.
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Thanks.
The sentinel method worked well in this case, but then Chris Losinger suggested method 3 -- using a container*. So I'm using that now. This technique has the added benefit that I can store the number of items allocated as well as the number of items in use -- sort of like how a List works in .net. I can add items up to the limit (I have no need to expand the array; I know how many items I need up front).
* Didn't we used to call that a Control Block? A simple way to avoid having bullions and bullions of function parameters?
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Quote: Didn't we used to call that a Control Block? A simple way to avoid having bullions and bullions of function parameters?
Of course I am aware of the general technique (pass a struct instead of tons of parameters, again Windows API docet), however it is the very first time I hear the term 'Control Block' used with such a meaning.
By the way, you are welcome.
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PIEBALD whips out his trusty "MS-DOS Programmer's Reference" (1993, "covers through version 6"!)... and it just says "structure", e.g. RWBLOCK structure.
And VMS uses "descriptors" which are similar.
"
The Descriptor
Classic C programming uses pointers to various structures, including null-terminated strings; ASCIZ strings. These are used within the OpenVMS standard C library, though most OpenVMS interfaces use descriptors. An OpenVMS construct that will be entirely new to even experienced C programmers is the string descriptor. This is typically a small data structure, containing the data length, data type, descriptor class, and data address for a chunk of data.
" -- http://labs.hoffmanlabs.com/node/273[^]
But I'm sure we used the term "Control Block" where I worked. Maybe it's from the UNIX culture? :shrug:
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Quote: "MS-DOS Programmer's Reference"
Well, Carlo cannot argue with The Truth. 
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Hi All,
While running a C++ Service in Wice indows 2008 Server i got below dump for service crash.
Crash Dump
------------
00 ntdll!ZwWaitForMultipleObjects+0xa
01 ntdll!RtlReportException+0x55e
02 ntdll!RtlReportException+0xbc
03 ntdll!RtlpNtMakeTemporaryKey+0x216
04 ntdll!_C_specific_handler+0x96
05 ntdll!wcstok_s+0x34be
06 ntdll!_chkstk+0x9d
07 ntdll!RtlRaiseException+0xf67
08 ntdll!RtlRaiseException+0x18d
09 ntdll!RtlpNtMakeTemporaryKey+0x1c0
0a ntdll!RtlpNtMakeTemporaryKey+0x3402
0b ntdll!RtlpNtMakeTemporaryKey+0x4000
0c ntdll!memset+0x160da
0d msvcr110!free+0x1c
0e wincli32!ConnectDlg+0x392
0f wincli32!OsGetCOPCLIVersion+0x7fed
10 ntdll!RtlActivateActivationContextUnsafeFast+0x114
11 ntdll!LdrShutdownThread+0x116
12 ntdll!RtlExitUserThread+0x3e
13 kernel32!BaseThreadInitThunk+0x15
14 ntdll!RtlUserThreadStart+0x34
please help me out.
Thanks,
Uday
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janaswamy uday wrote: please help me out.
With what? No one here has the remotest idea what program(s) you are running or where this error may have occurred.
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Here's a quick run-down of the NEC protocol. http://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol[^]
And here's some more general stuff: https://en.wikipedia.org/wiki/Consumer_IR[^]
A good place to look for the actual data/commands sent using the various protocols is in the microcontroller community. The Arduino/8501 forums/libraries have plenty of code available.
I once setup an arduino to record the incoming pulses from a remote. I then swapped the IR receiver module for a cheap 1mw laser - I can control the IR equipment from over 100m away now. 
Unfortunately, the code's on a machine I dont have access to now and I've long since forgotten where I got the info from, sorry.
"When I was 5 years old, my mother always told me that happiness was the key to life. When I went to school, they asked me what I wanted to be when I grew up. I wrote down 'happy'. They told me I didn't understand the assignment, and I told them they didn't understand life." - John Lennon
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Thank. 
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Hello there. I have this structure in Header1.h and instantiating this structure in Header2.h. When I try to initialize this instance, I get this runtime exception. Here is my skeleton of code
HEADER1.h
struct Student {
CString Name;
CString Address;
CString Phone;
};
HEADER2.h
class CHeader2Dlg {
Student student;
}
HEADER2.cpp
void CHeader2Dlg::SomeFunction()
{
student.Name = "";
student.Address = "";
student.Phone = "";
}
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Are you perhaps using the Unicode character set but assigning an ascii string?
Maybe it should be:
student.Name = L"";
The difficult we do right away...
...the impossible takes slightly longer.
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I changed that to L"" but in vein. Does it have to do anything with project settings ?
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I suspect there is something more going on than just the code you have posted. It sounds as if the CString object is not being instantiated.
Maybe if you could post more, relevant code.
The difficult we do right away...
...the impossible takes slightly longer.
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Header1.h
struct Account {
CString Name;
CString Address;
CString Phone;
};
Header2.h
class AccountDlg : public CDialog
{
Account account;
}
Header2.cpp
void AccountDlg::Load(int id)
{
CEdit* edit;
CComboBox *combobox;
account.Name= "asd"; account.Address= "asd";
account.Phone = "asd";
accountId = id;
accountSettings.AccountLoad(accountId,account);
}
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That doesn't reveal anything more than the first post. I think you should post the actual code, not an obfuscated version of it.
Show the "#includes" as well.
The difficult we do right away...
...the impossible takes slightly longer.
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