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To be honest, I tried to do a sample project for you, and found that VC will not compile most of your code. What you've posted, does not compile, and cannot compile. Even fixing the typos, VC will not compile it, another ( very non conformant ) compiler might, but VC will not.
Try creating a char **, like I said in the first place.
Christian Graus - C++ MVP
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This actually works just fine. Obviously, all funcB does is free the names, but they are correctly being passed through.
#include <string.h>
#include <malloc.h>
void funcB(const char ** names)
{
//the actual values names[0] and names[1] are to be accessed and used but they are null!!!???
//free names[0] and names[1]
free( (char*)names[0]);
free( (char*)names[1]);
}
void funcA()
{
int array = 4;
char ** Names = new char *[array];
int next = 0;
int i;
//initialise
for(i=0;i < array; ++ i)
{
Names[i]=NULL;
}
char * list = "Abc";
Names[ next ] = (char*) malloc( sizeof( char )*( strlen( list ) + 1 ) );
memcpy( Names[ next ],list,sizeof( char )*( strlen( list ) + 1 ) );
++next;
list = "cdefg";
Names[ next ] = (char*) malloc( sizeof( char )*( strlen( list ) + 1 ) );
memcpy( Names[ next ],list,sizeof( char )*( strlen( list ) + 1 ) );
printf("vsp list got is %s\n", Names[0] );
printf("vsp list got is %s\n", Names[1] );
funcB((const char**)Names);
}
int main(int argc, char* argv[])
{
printf("Hello World!\n");
funcA();
return 0;
}
Christian Graus - C++ MVP
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Hi...
Thanks for your time and help. I fixed it and Iam using char** Names but obviously, there is a bug with teh gcc compiler for it allowed me to do char*Names[array];
and returned no error or warnings.
But the program works now.
Thanks again. You have been a great help to me in understanding pointers and arrays and also gcc.
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No worries. If it accepted 'new', then it's compiling your code as C++.
I'm glad I helped. You'd do well to buy a book, or at least read up on the web on this stuff, to solidify the stuff we've worked on.
Christian Graus - C++ MVP
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Bear in mind that I used 'new' and you'll need to use 'malloc'
Christian Graus - C++ MVP
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Hi i used malloc instead of new as it is C.
Yup, Iam thinking of buying a book.
Can you recommend some good books worth buying and worth reading?
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The Kernegan (sp?) Ritchie book is the classic book on C. I learned C AFTER C++, so I did it entirely by working out which bits were missing, I have no other recommendations on C books.
Christian Graus - C++ MVP
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The Kernegan (sp?) Ritchie book is the classic book on C. I learned C AFTER C++, so I did it entirely by working out which bits were missing, I have no other recommendations on C books.
Christian Graus - C++ MVP
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Thanks for that. 
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char * Names[] = {};
where is this statement is placed?
in global scope? or inside the mail?
or as mentioned in the question?
If the definition of Names is done in funcA, then the scope of Names&lifetime would be lost.
I'm very sure if the definition is at main(), or global then it will work, provided that funcA is called before funcB.
To solve that u can move
char * Names[] = {};
to global scope or to main() and pass this as argument to the funcA()
Please let me know if I'm wrong.
--
Reddy
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iam working in multithreaded environments and hence
i have to declare the Names inside funcA only. and call func B within funcA.
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I doubt if ur program compiles!
instead u can try with this!!
#define ARRAY_SIZE 10
char *Names[ARRAY_SIZE] = {0,};
because in ur stmt for defining the Names, no size has been mentioned and causes compilation errors.
or u can try like this
char **Names = (char**)malloc(sizeof(char*)*ARRAY_SIZE);
then it should work.
--
Reddy
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Hi,
I'm pulling my hair out trying to do something simple. Thanks to the complicated and cryptic function signatures of MS with all that _in _out stuff I can't figure out how to do the following:
int pageNumber = 1;
int numPages = 2;
wstring wstr2Display; // I want to make this: L"1/2"
wstr2Display = ToString(pageNumber) + L"/" + ToString(numPages);
Seems I also can't directly 'add' the L"/".
Can someone share with me how to do this?
Thanks
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erm... I'm not sure where Microsoft comes into this ? Is this mananged C++, or is ToString your own function ? What is ToString returning ?
Christian Graus - C++ MVP
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MS only came into it because I can't read the cryptic help with all the extra stuff in the function signatures.
ToString() is just a 'dummy' function to allow me to write the line to show what I'm trying to do.
Actually, turns out what I really need is just to be able to concatenate and int + WCHAR + int into a WCHAR*.
Then I can use that WCHAR* to call GdiPlus::Drawstring()
So, in short, how do I convert an int to a WCHAR* representation?
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itoa() and the like, printf() and the like, ostringstream::operator <<() and the like.
You may be right
I may be crazy
-- Billy Joel --
Within you lies the power for good, use it!!!
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Like PJ said, your core problem is that you can add a wchar * to a wstring, you can't add three wchar* to each other. Your best bet IMO is an ostringstream, but itoa will do just fine ( well,itow if such a thing exists, or itot, perhaps ?)
Christian Graus - C++ MVP
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wstr2Display = ToString(pageNumber) + wstrin(L"/") + ToString(numPages);
try this!!
--
Reddy
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That would work if you put a g on the end of wstring 
And if ToString returns a wstring as well.
Christian Graus - C++ MVP
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Oy....
Ok, I've confused you guys. That ToString() function doesn't exist yet.
This is what I'm trying to do:
WCHAR text[] = L"3/4";
swprintf_s(text, 4, L"%c/%c", m_CurrentPage, m_NumPages);
to change text to L"1/2".
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If I have a *.lib file and corresponding header files how can I create a DLL? Any ideas? I don't have access to the source code. I have been told that I can create the dll using the lib file, but not sure quite where to go. Am I right in thinking I'll have to write some code to 'wrap' the lib file?
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Yes. You need to 'wrap' each function in the LIB you want exposed from the DLL.
Or you can make a 'higher level' interface to the library by aggregating function callss into easier to use constructs of action, for example.
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I have a client and a server. The server can accept only 2 connections. The client is written with VC++ and the server is written in C++.
Client:
<br />
...<br />
result = mySck.Connect(ip address, port number);<br />
if (!result)<br />
{<br />
...<br />
}<br />
else<br />
{<br />
...<br />
}<br />
Server:
<br />
#define QUEUE_SZ 0<br />
...<br />
...<br />
result = listen(svr_sck, QUEUE_SZ);<br />
...<br />
Worker thread:
<br />
#define MAX_SCKS 2<br />
int totoal_scks = 0;<br />
<br />
while(1)<br />
{<br />
if (total_scks < MAX_SCKS)<br />
{<br />
printf("Ready to accept connection");<br />
tmpSck = accept(svr_sck, (struct sockaddr *) &stClntAddr, &sckAddrSize);<br />
if (tmpSck == ERROR)<br />
{<br />
...<br />
}<br />
else<br />
{<br />
total_scks++;<br />
...<br />
}<br />
}<br />
else<br />
{<br />
...<br />
}<br />
}<br />
There is more to the code but this should do for now.
After I connect 2 clients, the server no longer prints that it is ready to accept connections. This means that I am not executing the accept statement a 3rd time. This is what I am expecting.
The problem is:
However when I try to connect a 3rd client, it looks like the server still accepts the connection but I am not executing the code after the accept statement and total_scks is still 2. On the client side the Connect function returns 1 which means that the connection was successful. How can this happenned?
If QUEUE_SZ is 0, I can connect a 3rd connection but on the 4th, the Connect function returns 0. If QUEUE_SZ is 1, I can connect a 3rd and a 4th connections but on the 5th, Connect returns 0...and so on.
Anybody can help me with this?
jpyp
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IMO you left out the most important parts of code in your post - the creation of the sockets.
There's two things going on here, but I can only help with one since you left the rest out.
jpyp wrote: If QUEUE_SZ is 0, I can connect a 3rd connection but on the 4th, the Connect function returns 0.
If QUEUE_SZ is 1, I can connect a 3rd and a 4th connections but on the 5th, Connect returns 0...and so on.
The backlog parameter of the listen() function sets the maximum number of pending connections.
That's how many connections will sit queued until you accept or refuse them. When the queue
is full, additional incoming connections should be immediately refused.
I'm not sure what the behavior is when you set this to 0. Regardless, since you allow two
simultaneous connections, you might as well set this to at least 2 and refuse connections some
other way.
As for the unknowns, what protocol are you using? How are you creating the sockets?
Assuming TCP then it gets a little tricky rejecting connections with Winsock because of security
issues related to SYN attacks (thank the idiot "hackers").
Based on the code you've shown, I would expect the 3rd client's Connect() call to block until
it times out. If you put a breakpoint on the accept() call in the server, it should only get
called twice with 3 connection attempts, correct?
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You are correct. Because of my total_scks counter, accept() only gets called twice. However since I got your reply I found a little more info from the Tornado help docs. I now understand a lot better what is going on and I suspect a lot of people do not know this:
The queue size parameter in listen() does not affect the number of simultaneous connections that the server will accept. You need a counter like I have implemented to restrict the number of simultaneous connections. In my case if I already have 2 connections and I have 5 for queue size as parameter to the listen() function, then the server will queue up to 5 new clients. Once one of the current connections closes, the first queued client will then be accepted.
What I now understand is that listen() actually makes the connection with the client, not accept(). Therefore if you have a counter of 2 and a queue of 5, you could actually have 7 clients connected at once but only 2 of these will be accepted and transfering data. The connect() function on the clients that are queued returns successful because listen() on the server made the connection.
This last point is very interesting and brings me to my next question:
How can I detect on the client that the connection is not yet accepted by the server or that I lost the connection with the server?
Thanks for your help?
jpyp
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