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• Is it good practice to initialize array in C/C++?

  - by sand

  I recently encountered a case where I need to compare two files (golden and expected) for verification of test results and even though the data written to both the files were same, the files does not match. On further investigation, I found that there is a structure which contains some integers and a char array of 64 bytes, and not all the bytes of char array were getting used in most of the cases and unused fields from the array contain random data and that was causing the mismatch. This brought me ask the question whether it is good practice to initialize the array in C/C++ as well, as it is done in Java?

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• Dereferencing deleted pointers always result in an Access Violation ??

  - by m3rLinEz

  I have a very simple C++ code here: char *s = new char[100]; strcpy(s, "HELLO"); delete [] s; int n = strlen(s); If I run this code from Visual C++ 2008 by pressing F5 (Start Debugging,) this always result in crash (Access Violation.) However, starting this executable outside the IDE, or using the IDE's Ctrl+F5 (Start without Debugging) doesn't result in any crash. What could be the difference? I also want to know if it's possible to stably reproduce the Access Violation crash caused from accessing deleted area? Is this kind of crash rare in real-life?

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• Best way to implement a data structure in PHP ?

  - by Double Gras

  Hi, I want to use some kind of data structure in PHP (5.2), mainly in order to not pollute the global namespace. I think about two approaches, using an array or a class. Could you tell me which approach is better ? Thanks $SQL_PARAMETERS = array ( 'server' => '127.0.0.1', 'login' => 'root'); class SqlParameters { const SERVER = '127.0.0.1'; const LOGIN = 'root'; } echo $SQL_PARAMETERS['server']; echo SqlParameters::SERVER;

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• Need help with displaying the message correctly in the pole display always starting at the beginning

  - by SA

  Hi, I am using an HP RS232 pole display with the following setting: Char type: USA/Europe (default) Command mode: EPSON (default) Baud rate: 9600, n , 8, 1 (default?) Passthru None (Default) Here's the code using System.IO.Ports; private SerialPort port; port = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One); port.Handshake = Handshake.None; Port.WriteLine("Welocome to something something"); It has 2 lines consisting of 20 characters each with a total of 40 characters. I have no control how and where the characters get displayed. I would like it to always begin on line 1 position 1 but as I said earlier how would I be able to do that. The same program if I run again and again it moves a character to the left. I have set it to accept ASCII char set and so I am able to type as is visble in the Writeline message

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• matlab: putting a circled number onto a graph

  - by Jason S

  I want to put a circled number on a graph as a marker near (but not on) a point. Sounds easy, but I also want to be invariant of zoom/aspect ratio changes. Because of this invariant, I can't draw a circle as a line object (without redrawing it upon rescale); if I use a circle marker, I'd have to adjust its offset upon rescale. The simplest approach I can think of is to use the Unicode or Wingdings characters ① ② ③ etc. in a string for the text() function. But unicode doesn't seem to work right, and the following sample only works with ① and not for the other numbers (which yield rectangle boxes): works: clf; text(0.5,0.5,char(129),'FontName','WingDings') doesn't work (should be a circled 2): clf; text(0.5,0.5,char(130),'FontName','WingDings') What gives, and can anyone suggest a workaround?

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• int[] to string c#

  - by Robin Webdev

  Hi I'm developing an client application in C# and the server is written in c++ the server uses: inline void StrToInts(int *pInts, int Num, const char *pStr) { int Index = 0; while(Num) { char aBuf[4] = {0,0,0,0}; for(int c = 0; c < 4 && pStr[Index]; c++, Index++) aBuf[c] = pStr[Index]; *pInts = ((aBuf[0]+128)<<24)|((aBuf[1]+128)<<16)|((aBuf[2]+128)<<8)|(aBuf[3]+128); pInts++; Num--; } // null terminate pInts[-1] &= 0xffffff00; } to convert an string to int[] in my c# client i recieve: int[4] { -14240, -12938, -16988, -8832 } How do I convert the array back to an string? I don't want to use unsafe code (e.g. pointers) Any of my tries resulted in unreadable strings.

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• How would I implement code in a .h file into the main.cpp file?

  - by Lea

  I have a c++ project I am working on. I am a little stumped at the moment. I need a little help. I need to implement code from the .h file into the main.cpp file and I am not sure how to do that. For example code code from main.cpp: switch (choice){ case 1: // open an account { cout << "Please enter the opening balence: $ "; cin >> openBal; cout << endl; cout << "Please enter the account number: "; cin >> accountNum; cout << endl; break; } case 2:// check an account { cout << "Please enter the account number: "; cin >> accountNum; cout << endl; break; } and code from the .h file: void display(ostream& out) const; // displays every item in this list through out bool retrieve(elemType& item) const; // retrieves item from this list // returns true if item is present in this list and // element in this list is copied to item // false otherwise // transformers void insert(const elemType& item); // inserts item into this list // preconditions: list is not full and // item not present in this list // postcondition: item is in this list In the .h file you would need to use the void insert under transformer in the main.cpp under case 1. How would you do that? Any help is apprecaited. I hope I didn't confuse anyone on what I am needing to know how to do. Thanks

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• How can I tell if an ADODB::_RecordsetPtr has already been created?

  - by scottm

  I am trying to write a class that uses ADO to retrieve SQL records. The intent is for the class to maintain one private recordset an other methods move forward, retrieve fields, etc. This is a basic example of my class: class SqlADO { private: ADODB::_RecordsetPtr m_recordset; public: void Open(); //open the connection void Execute(const char* sql); // creates or replaces current recordset void Next(); //moves recordset cursor forward void Field(const char* fieldName); //retrieves field name from current record of the recordset }; My Questions: In the Execute method, how can I check to see that the recordset instance has been created (or do I need to) so that I can close it first? Do you know of any good ADO COM Interop references?

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• Preprocessor directive to test if this is C or C++

  - by Collin

  I'm trying to find a standard macro which will test whether a header file is being compiled as C or as C++. The purpose of this is that the header may be included by either C or C++ code, and must behave slightly differently depending on which. Specifically: In C, I need this to be the code: extern size_t insert (const char*); In C++, I need this to be the code: extern "C" size_t insert (const char*); Additionally, is there a way to avoid putting #ifdef's around every declaration in the header?

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• [c]how to take input for a character pionter without using fget?

  - by ashish yadav

  consider the code include int main() {char* a; scanf("%s",a);//&a and &a[0] give same results-crashes printf("%s",); return 0; } why does this code results in crashing?whereas this code using character array works fine? include int main() {char a[100]; scanf("%s",&a[0]);//works fine printf("%s",a); return 0; } the difference being character array and pointer?but i knew that pointer just points to the first element that is &a[0] should work fine but upper code crashes for all three that is a,&a and &a[0]? the main thing i would to gather is how can i take input of a character pointer if i insist on using scanf only? i apologize if i am not clear. thanks in advance:)

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• Why isn't my IO executed in order?

  - by HaskellElephant

  Hi, I'm having some fun learning about the haskell IO. However in my recent exploration of it I have encountered some problems with IO not executing in order, even inside a do construct. In the following code I am just keeping track of what cards are left, where the card is a tuple of chars (one for suit and one for value) then the user is continously asked for wich cards have been played. I want the putStr to be executed between each input, and not at the very end like it is now. module Main where main = doLoop cards doLoop xs = do putStr $ show xs s <- getChar n <- getChar doLoop $ remove (s,n) xs suits = "SCDH" vals = "A23456789JQK" cards = [(s,n) | s <- suits, n <- vals] type Card = (Char,Char) remove :: Card -> [Card] -> [Card] remove card xs = filter (/= card) xs

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• Can you use #defined values in if statements (In C programs)?

  - by Jordan S

  I am new at C programming. I thought when you type something like #define Const 5000 that the compiler just replaces every instance of Const with 5000 at compile time. Is that wrong? I try doing this in my code and I get a syntax error. Why can't i do this? #define STEPS_PER_REV 12345 ... in some function if(CurrentPosition >= STEPS_PER_REV) { // do some stuff here } The compiler complains about the if statement with a syntax error that gives me no details.

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• Use C function in C++ program; "multiply-defined" error

  - by eom

  I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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• java decmail string to AS 3.0 conversion procedure

  - by Jack Smith

  Hello, I have a problem with conversion java code to action script 3. Anyone can help with code translation? Thanks. public static short[] decmail_str_to_binary_data(String s) { short[] data = new short[s.length()/2]; for (int i = 0; i < s.length(); i += 2) { char c1 = s.charAt(i); char c2 = s.charAt(i + 1); int comb = Character.digit(c1, 16) & 0xff; comb <<= 4; comb += Character.digit(c2, 16) & 0xff; data[i/2] = (short)comb; } return data; }

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• how to send Zip(binary) file Through HTTP post method in mFC/C++?

  - by Mahantesh

  I am posting the file to server and its working fine, But the my code fails when i try to post the .zip file. May be my code is wrong in the reading the zip file contents data. ifstream::pos_type size; char * memblock; ifstream file ("example.zip", ios::in|ios::binary|ios::ate); if (file.is_open()) { size = file.tellg(); memblock = new char [size]; file.seekg (0, ios::beg); file.read (memblock, size); file.close(); postBody.AppendFormat("Content-Disposition: form-data; name=\"datafile\"; filename=\"%s\"; \r\n\n%s", zipFilePath, memblock); postBody.AppendFormat("\r\n--%s--\r\n", boundary); }

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• strenge exception phenomenon in win7

  - by Level 2

  Hello all, I spot some interesting artcles about exception handle in codeproject http://www.codeproject.com/KB/cpp/seexception.aspx after reading, I decided to do some experiment. The first time I try to excute the following code char *p; p[0] = 0; The program died without question. But After serveral time I execute the same problem binary code. It magically did fine. even the following code is doing well. any clue or explain? char *p p[1000] = 'd'; cout<<p[1000]<<endl; my os is windows 7 64bit and compiler is vs2008 rc1.

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• C String input confusion

  - by ahref

  C really isn't my strong point and after reading 3 chapters of a book on the subject and spending ages trying to get stuff working it just doesn't: #include <stdio.h> char *a,*b; int main( ) { char input[10]; fgets(input,sizeof input, stdin); a = input; fgets(input,sizeof input, stdin); b = input; printf("%s : %s",a,b); } I've isolated the problem from my main project. This code is meant to read in two strings and then print them however it seems to be setting a and b to point to input. Sample output from this code when A and B are entered is(don't worry about the \n's i can remove them): A B B : B How do i store the value of input in another variable eg. a or b so that in the above case A B A : B Is output? Thanks

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• an error "variable of field declared void"

  - by lego69

  I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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• Why isn't the copy constructor elided here?

  - by Jesse Beder

  (I'm using gcc with -O2.) This seems like a straightforward opportunity to elide the copy constructor, since there are no side-effects to accessing the value of a field in a bar's copy of a foo; but the copy constructor is called, since I get the output meep meep!. #include <iostream> struct foo { foo(): a(5) { } foo(const foo& f): a(f.a) { std::cout << "meep meep!\n"; } int a; }; struct bar { foo F() const { return f; } foo f; }; int main() { bar b; int a = b.F().a; return 0; }

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• strcat() won't exit

  - by Tristan Sebens

  I'm trying to implement a very basic server in C, one part of which is constructing HTTP headers. To do this I have written a class called header_builder, which basically constructs the headers for me. One of the most basic methods of this class is append_header_line, shown below: void append_header_line( const char *line, char *hdr ) { printf("Adding header line\n"); strcat( hdr, line ); printf("Line added. Adding ending.\n"); strcat( hdr, "\r\n" ); printf("Success\n"); } All it's supposed to do is tack the "line" parameter onto the end of the "hdr" parameter, and then add "\r\n" to the end of it all. The problem is that the first strcat call never exits. When I run this code, all it does is say: Adding header line Which means that the following lines never execute, and I can't figure out why. Any thoughts?

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• Create a modifiable string literal in C++

  - by Anne

  Is it possible to create a modifiable string literal in C++? For example: char* foo[] = { "foo", "foo" }; char* afoo = foo[0]; afoo[2] = 'g'; // access violation This produces an access violation because the "foo"s are allocated in read only memory (.rdata section I believe). Is there any way to force the "foo"s into writable memory (.data section)? Even via a pragma would be acceptable! (Visual Studio compiler) I know I can do strdup and a number of other things to get around the problem, but I want to know specifically if I can do as I have asked. :)

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• Why timed lock doesnt throws a timeout exception in C++0x?

  - by Vicente Botet Escriba

  C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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• not working function with no errors

  - by aya

  hello.. I've implemented a function to display an avl tree after inserting nodes into it like this template void AVLtree::display() const { display(Proot); } template void AVLtree::display(Node * ptr) const { if(ptr==0) return ; cout<value<<" "; display(ptr-Pleft); display(ptr-Pright); } after compiling,there were no errors ,the program worked but nothing were printed on the screen help me please....!! thanks

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• How to get size of file in visual c++?

  - by karikari

  Below is my code. My problem is, my destination file always has a lot more strings than the originating file. Then, inside the for loop, instead of using i < sizeof more, I realized that I should use i < sizeof file2 . Now my problem is, how to get the size of file2? int i = 0; FILE *file2 = fopen(LOG_FILE_NAME,"r"); wfstream file3 (myfile, ios_base::out); // char more[1024]; char more[SIZE-OF-file2]; for(i = 0; i < SIZE-OF-file2 ; i++) { fgets(more, SIZE-OF-file2, file2); file3 << more; } fclose(file2); file3.close();

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• Strange exception phenomenon in Windows 7

  - by Level 2

  I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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