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  • cast operator to base class within a thin wrapper derived class

    - by miked
    I have a derived class that's a very thin wrapper around a base class. Basically, I have a class that has two ways that it can be compared depending on how you interpret it so I created a new class that derives from the base class and only has new constructors (that just delegate to the base class) and a new operator==. What I'd like to do is overload the operator Base&() in the Derived class so in cases where I need to interpret it as the Base. For example: class Base { Base(stuff); Base(const Base& that); bool operator==(Base& rhs); //typical equality test }; class Derived : public Base { Derived(stuff) : Base(stuff) {}; Derived(const Base& that) : Base(that) {}; Derived(const Derived& that) : Base(that) {}; bool operator==(Derived& rhs); //special case equality test operator Base&() { return (Base&)*this; //Is this OK? It seems wrong to me. } }; If you want a simple example of what I'm trying to do, pretend I had a String class and String==String is the typical character by character comparison. But I created a new class CaseInsensitiveString that did a case insensitive compare on CaseInsensitiveString==CaseInsensitiveString but in all other cases just behaved like a String. it doesn't even have any new data members, just an overloaded operator==. (Please, don't tell me to use std::string, this is just an example!) Am I going about this right? Something seems fishy, but I can't put my finger on it.

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  • using switch in strings

    - by xtemer
    guys me trying to use switch in strings by first coverting string into char and then apply switch but still didnt done it....here is my code..help me out.. import javax.swing.*; import java.io.*; class HappyBirthday { public static void main(String[] args) throws IOException { String Month; char[] Months = Month.toCharArray(); BufferedReader dataIn= new BufferedReader(new InputStreamReader(System.in)); System.out.println("Please enter your month."); Month = JOptionPane.showInputDialog("enter month"); String month1={"January","feb"}; char[] month2 = month1.toCharArray(); // String s=month1.equals(Month); //System.out.print(month2Array[0]); switch (month2) { case 0: System.out.println("kool"); break; case 1: System.out.println("not kool"); break; default: }}} /** if (month1[1].equals(Month)) System.out.println("kool"); else if(month1[0].equals(Month)) System.out.println("kooooooooooooool"); else System.out.println("Big kooooool"); **/

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  • Potential g++ template bug?

    - by Evan Teran
    I've encountered some code which I think should compile, but doesn't. So I'm hoping some of the local standards experts here at SO can help :-). I basically have some code which resembles this: #include <iostream> template <class T = int> class A { public: class U { }; public: U f() const { return U(); } }; // test either the work around or the code I want... #ifndef USE_FIX template <class T> bool operator==(const typename A<T>::U &x, int y) { return true; } #else typedef A<int> AI; bool operator==(const AI::U &x, int y) { return true; } #endif int main() { A<int> a; std::cout << (a.f() == 1) << std::endl; } So, to describe what is going on here. I have a class template (A) which has an internal class (U) and at least one member function which can return an instance of that internal class (f()). Then I am attempting to create an operator== function which compares this internal type to some other type (in this case an int, but it doesn't seem to matter). When USE_FIX is not defined I get the following error: test.cc: In function 'int main()': test.cc:27:25: error: no match for 'operator==' in 'a.A<T>::f [with T = int]() == 1' Which seems odd, because I am clearly (I think) defining a templated operator== which should cover this, in fact if I just do a little of the work for the compiler (enable USE_FIX), then I no longer get an error. Unfortunately, the "fix" doesn't work generically, only for a specific instantiation of the template. Is this supposed to work as I expected? Or is this simply not allowed? BTW: if it matters I am using gcc 4.5.2.

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  • Is the following C code safe?

    - by lali
    #include<cstdio> #include<stdlib.h> int main() { char* ptr=NULL; printf("%s",ptr); return 0; } It prints (null) as output. The above is a sample code. In real code i get char* as a return of a function and i wish to print the character string for logging. However, NULL is also a valid return value of that function and so i am wondering if a null check is required before printing the character string? char* ptr=someFuncion(); // do i need the following if statement? if(ptr!=NULL) { printf("%s",ptr); } I just want to be sure that the output would be same i.e if ptr=NULL then output should be (null) on all platforms and compilers and the above code(without if statement) would not crash on any C standard compatible platform. In short, is the above code(without the if statement) standard compatible? Thanks for your help and patience :) Regards lali

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  • what does this attempted trojan horse code do?

    - by bstullkid
    It looks like this just sends a ping, but whats the point of that when you can just use ping? /* WARNING: this is someone's attempt at writing a malware trojan. Do not compile and *definitely* don't install. I added an exit as the first line to avoid mishaps - msw */ int main (int argc, char *argv[]) { exit(1); unsigned int pid = 0; char buffer[2]; char *args[] = { "/bin/ping", "-c", "5", NULL, NULL }; if (argc != 2) return 0; args[3] = strdup(argv[1]); for (;;) { gets(buffer); /* FTW */ if (buffer[0] == 0x6e) break; switch (pid = fork()) { case -1: printf("Error Forking\n"); exit(255); case 0: execvp(args[0], args); exit(1); default: break; } } return 255; }

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  • Why this code generates different numbers?

    - by frbry
    Hello, I have this function that creates a unique number for hard-disk and CPU combination. DWORD hw_hash() { char drv[4]; char szNameBuffer[256]; DWORD dwHddUnique; DWORD dwProcessorUnique; DWORD dwUniqueKey; char *sysDrive = getenv ("SystemDrive"); strcpy(drv, sysDrive); drv[2] = '\\'; drv[3] = 0; GetVolumeInformation(drv, szNameBuffer, 256, &dwHddUnique, NULL, NULL, NULL, NULL); SYSTEM_INFO si; GetSystemInfo(&si); dwProcessorUnique = si.dwProcessorType + si.wProcessorArchitecture + si.wProcessorRevision; dwUniqueKey = dwProcessorUnique + dwHddUnique; return dwUniqueKey; } It returns different numbers if I format my hard-disk and install a new Windows. Any ideas, why? Thank you. Edit: OK, Got it: This function returns the volume serial number that the operating system assigns when a hard disk is formatted. To programmatically obtain the hard disk's serial number that the manufacturer assigns, use the Windows Management Instrumentation (WMI) Win32_PhysicalMedia property SerialNumber. I should do more research before posting my problems online. Sorry to bother you, let's keep this here in case anybody else can need it.

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  • Increment a value from AAA to ZZZ with cyclic rotation

    - by www.openidfrance.frfxkim
    Hi all, I need to code a method that increment a string value from AAA to ZZZ with cyclic rotation (next value after ZZZ is AAA) Here is my code: public static string IncrementValue(string value) { if (string.IsNullOrEmpty(value) || value.Length != 3) { string msg = string.Format("Incorrect value ('{0}' is not between AAA and ZZZ)", value); throw new ApplicationException(msg); } if (value == "ZZZ") { return "AAA"; } char pos1 = value[0]; char pos2 = value[1]; char pos3 = value[2]; bool incrementPos2 = false; bool incrementPos1 = false; if (pos3 == 'Z') { pos3 = 'A'; incrementPos2 = true; } else { pos3++; } if (incrementPos2 && pos2 == 'Z') { pos2 = 'A'; incrementPos1 = true; } else { if (incrementPos2) { if (pos2 == 'Z') { pos2 = 'A'; incrementPos1 = true; } pos2++; } } if (incrementPos1) { pos1++; } return pos1.ToString() + pos2.ToString() + pos3.ToString(); } I know this piece of code is quite dirty and not very efficient but I dont know how to do it properly. How is secured this snippet? (this will only run on windows plaform) How can I optimize-it and make it more readable ? Thanks for your comments

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  • Rapid calls to fread crashes the application

    - by Slynk
    I'm writing a function to load a wave file and, in the process, split the data into 2 separate buffers if it's stereo. The program gets to i = 18 and crashes during the left channel fread pass. (You can ignore the couts, they are just there for debugging.) Maybe I should load the file in one pass and use memmove to fill the buffers? if(params.channels == 2){ params.leftChannelData = new unsigned char[params.dataSize/2]; params.rightChannelData = new unsigned char[params.dataSize/2]; bool isLeft = true; int offset = 0; const int stride = sizeof(BYTE) * (params.bitsPerSample/8); for(int i = 0; i < params.dataSize; i += stride) { std::cout << "i = " << i << " "; if(isLeft){ std::cout << "Before Left Channel, "; fread(params.leftChannelData+offset, sizeof(BYTE), stride, file + i); std::cout << "After Left Channel, "; } else{ std::cout << "Before Right Channel, "; fread(params.rightChannelData+offset, sizeof(BYTE), stride, file + i); std::cout << "After Right Channel, "; offset += stride; std::cout << "After offset incr.\n"; } isLeft != isLeft; } } else { params.leftChannelData = new unsigned char[params.dataSize]; fread(params.leftChannelData, sizeof(BYTE), params.dataSize, file); }

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  • Looks like COM object is created, but JScript fails to get a reference

    - by damix911
    I'm using the following code to create a COM component that I have developed and registered. var mycom = new ActiveXObject("Mirabilis.ComponentServices.1"); mycom.SetFirstNumber(5); mycom.SetSecondNumber(3); The first line runs fine, while if I alter the ProgID (that is, the string passed to ActiveXObject) I get the message Automation server can't create object. This suggests that at least the basics of the registration mechanism are working properly. I integrated some logging calls into the DLL. When I run the script I get the proof into the log file that both this call to QueryInterface: STDAPI DllGetClassObject( const CLSID &clsid, const IID &iid, void **ppv) { ... CAddFactory *pAddFact = new CAddFactory; ... HRESULT hr = pAddFact->QueryInterface(iid, ppv); if (hr == S_OK) writeToLogFile("Class QueryInterface returned S_OK"); else writeToLogFile("Class QueryInterface failed"); return hr; ... } and this one: HRESULT __stdcall CAddFactory::CreateInstance( IUnknown *pUnknownOuter, const IID &iid, void **ppv) { ... CAddObj *pObject = new CAddObj; ... HRESULT hr = pObject->QueryInterface(iid, ppv); if (hr == S_OK) writeToLogFile("Object QueryInterface returned S_OK"); else writeToLogFile("Object QueryInterface failed"); return hr; ... } return S_OK. However, when JScript gets to line 3 of the script, I get the following error message: 'mycom' is null or not an object Why is this happening? It looks like JScript should be able to obtain a reference. Some attempts I made I tried to return S_FALSE from DllCanUnloadNow to be sure that the DLL will not be unloaded, just in case, but with no luck.

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  • Trouble with an depreciated constructor visual basic visual studio 2010

    - by VBPRIML
    My goal is to print labels with barcodes and a date stamp from an entry to a zebra TLP 2844 when the user clicks the ok button/hits enter. i found what i think might be the code for this from zebras site and have been integrating it into my program but part of it is depreciated and i cant quite figure out how to update it. below is what i have so far. The printer is attached via USB and the program will also store the entered numbers in a database but i have that part done. any help would be greatly Appreciated.   Public Class ScanForm      Inherits System.Windows.Forms.Form    Public Const GENERIC_WRITE = &H40000000    Public Const OPEN_EXISTING = 3    Public Const FILE_SHARE_WRITE = &H2      Dim LPTPORT As String    Dim hPort As Integer      Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String,                                                                           ByVal dwDesiredAccess As Integer,                                                                           ByVal dwShareMode As Integer, <MarshalAs(UnmanagedType.Struct)> ByRef lpSecurityAttributes As SECURITY_ATTRIBUTES,                                                                           ByVal dwCreationDisposition As Integer, ByVal dwFlagsAndAttributes As Integer,                                                                           ByVal hTemplateFile As Integer) As Integer          Public Declare Function CloseHandle Lib "kernel32" Alias "CloseHandle" (ByVal hObject As Integer) As Integer      Dim retval As Integer           <StructLayout(LayoutKind.Sequential)> Public Structure SECURITY_ATTRIBUTES          Private nLength As Integer        Private lpSecurityDescriptor As Integer        Private bInheritHandle As Integer      End Structure            Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OKButton.Click          Dim TrNum        Dim TrDate        Dim SA As SECURITY_ATTRIBUTES        Dim outFile As FileStream, hPortP As IntPtr          LPTPORT = "USB001"        TrNum = Me.ScannedBarcodeText.Text()        TrDate = Now()          hPort = CreateFile(LPTPORT, GENERIC_WRITE, FILE_SHARE_WRITE, SA, OPEN_EXISTING, 0, 0)          hPortP = New IntPtr(hPort) 'convert Integer to IntPtr          outFile = New FileStream(hPortP, FileAccess.Write) 'Create FileStream using Handle        Dim fileWriter As New StreamWriter(outFile)          fileWriter.WriteLine(" ")        fileWriter.WriteLine("N")        fileWriter.Write("A50,50,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrNum) 'prints the tracking number variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.Write("A50,100,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrDate) 'prints the date variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.WriteLine("P1")        fileWriter.Flush()        fileWriter.Close()        outFile.Close()        retval = CloseHandle(hPort)          'Add entry to database        Using connection As New SqlClient.SqlConnection("Data Source=MNGD-LABS-APP02;Initial Catalog=ScannedDB;Integrated Security=True;Pooling=False;Encrypt=False"), _        cmd As New SqlClient.SqlCommand("INSERT INTO [ScannedDBTable] (TrackingNumber, Date) VALUES (@TrackingNumber, @Date)", connection)            cmd.Parameters.Add("@TrackingNumber", SqlDbType.VarChar, 50).Value = TrNum            cmd.Parameters.Add("@Date", SqlDbType.DateTime, 8).Value = TrDate            connection.Open()            cmd.ExecuteNonQuery()            connection.Close()        End Using          'Prepare data for next entry        ScannedBarcodeText.Clear()        Me.ScannedBarcodeText.Focus()      End Sub

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  • verifying the signature of x509

    - by sid
    Hi All, While verifying the certificate I am getting EVP_F_EVP_PKEY_GET1_DH My Aim - Verify the certificate signature. I am having 2 certificates : 1. a CA certificate 2. certificate issued by CA. I extracted the 'RSA Public Key (key)' Modulus From CA Certificate using, pPublicKey = X509_get_pubkey(x509); buf_len = (size_t) BN_num_bytes (bn); key = (unsigned char *)malloc (buf_len); n = BN_bn2bin (bn, (unsigned char *) key); if (n != buf_len) LOG(ERROR," : key error\n"); if (key[0] & 0x80) LOG(DEBUG, "00\n"); Now, I have CA public key & CA key length and also having certificate issued by CA in buffer, buffer length & public key. To verify the signature, I have following code int iRet1, iRet2, iRet3, iReason; iRet1 = EVP_VerifyInit(&md_ctx, EVP_sha1()); iRet2 = EVP_VerifyUpdate(&md_ctx, buf, buflen); iRet3 = EVP_VerifyFinal(&md_ctx, (const unsigned char *)CAkey, CAkeyLen, pubkey); iReason = ERR_get_error(); if(ERR_GET_REASON(iReason) == EVP_F_EVP_PKEY_GET1_DH) { LOG(ERROR, "EVP_F_EVP_PKEY_GET1_DH\n"); } LOG(INFO,"EVP_VerifyInit returned %d : EVP_VerifyUpdate returned %d : EVP_VerifyFinal = %d \n", iRet1, iRet2, iRet3); EVP_MD_CTX_cleanup(&md_ctx); EVP_PKEY_free(pubkey); if (iRet3 != 1) { LOG(ERROR,"EVP_VerifyFinal() failed\n"); ret = -1; } LOG(INFO,"signature is valid\n"); I am unable to figure out What might went wrong??? Please if anybody faced same issues? What EVP_F_EVP_PKEY_GET1_DH Error means? Thanks in Advance - opensid

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  • Pointers to structs

    - by Bobby
    I have the following struct: struct Datastore_T { Partition_Datastores_T cmtDatastores; // bytes 0 to 499 Partition_Datastores_T cdhDatastores; // bytes 500 to 999 Partition_Datastores_T gncDatastores; // bytes 1000 to 1499 Partition_Datastores_T inpDatastores; // bytes 1500 1999 Partition_Datastores_T outDatastores; // bytes 2000 to 2499 Partition_Datastores_T tmlDatastores; // bytes 2500 to 2999 Partition_Datastores_T sm_Datastores; // bytes 3000 to 3499 }; I want to set a char* to struct of this type like so: struct Datastore_T datastores; // Elided: datastores is initialized with data here char* DatastoreStartAddr = (char*)&datastores; memset(DatastoreStartAddr, 0, sizeof(Datastore_T)); The problem I have is that the value that DatastoreStartAddr points to always has a value of zero when it should point to the struct that has been initialized with data. Meaning if I change the values in the struct using the struct directly, the values pointed to by DatastoreStartAddr should also change b/c they are pointing to the same address. But this is not happening. What am I doing wrong?

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  • Android - Read PNG image without alpha and decode as ARGB_8888

    - by loki666
    I try to read an image from sdcard (in emulator) and then create a Bitmap image with the BitmapFactory.decodeByteArray method. I set the options: options.inPrefferedConfig = Bitmap.Config.ARGB_8888 options.inDither = false Then I extract the pixels into a ByteBuffer. ByteBuffer buffer = ByteBuffer.allocateDirect(width*height*4) bitmap.copyPixelsToBuffer(buffer) I use this ByteBuffer then in the JNI to convert it into RGB format and want to calculate on it. But always I get false data - I test without modifying the ByteBuffer. Only thing I do is to put it into the native method into JNI. Then cast it into a unsigned char* and convert it back into a ByteBuffer before returning it back to Java. unsigned char* buffer = (unsinged char*)(env->GetDirectBufferAddress(byteBuffer)) jobject returnByteBuffer = env->NewDirectByteBuffer(buffer, length) Before displaying the image I get data back with bitmap.copyPixelsFromBuffer( buffer ) But then it has wrong data in it. My Question is if this is because the image is internally converted into RGB 565 or what is wrong here? ..... Have an answer for it: - yes, it is converted internally to RGB565. Does anybody know how to create such an bitmap image from PNG with ARGB8888 pixel format? If anybody has an idea, it would be great!

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  • fgets in c don't return a portion of an string

    - by Marc
    Hi! I'm totally new in C, and I'm trying to do a little application that searches a string into a file, my problem is that I need to open a big file (more than 1GB) with just one line inside and fgets return me the entire file (I'm doing test with a 10KB file). actually this is my code: #include <stdio.h> #include <string.h> int main(int argc, char *argv[]) { char *search = argv[argc-1]; int retro = strlen(search); int pun = 0; int sortida; int limit = 10; char ara[20]; FILE *fp; if ((fp = fopen ("SEARCHFILE", "r")) == NULL){ sortida = -1; exit (1); } while(!feof(fp)){ if (fgets(ara, 20, fp) == NULL){ break; } //this must be a 20 bytes line, but it gets the entyre 10Kb file printf("%s",ara); } sortida = 1; if(fclose(fp) != 0){ sortida = -2; exit (1); } return 0; } What can I do to find an string into a file? I'v tried with GREP but it don't helps, because it returns the position:ENTIRE_STRING. I'm open to ideas. Thanks in advance!

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  • Can someone explain me this code ?

    - by VaioIsBorn
    #include <stdio.h> #include <unistd.h> #include <string.h> int good(int addr) { printf("Address of hmm: %p\n", addr); } int hmm() { printf("Win.\n"); execl("/bin/sh", "sh", NULL); } extern char **environ; int main(int argc, char **argv) { int i, limit; for(i = 0; environ[i] != NULL; i++) memset(environ[i], 0x00, strlen(environ[i])); int (*fptr)(int) = good; char buf[32]; if(strlen(argv[1]) <= 40) limit = strlen(argv[1]); for(i = 0; i <= limit; i++) { buf[i] = argv[1][i]; if(i < 36) buf[i] = 0x41; } int (*hmmptr)(int) = hmm; (*fptr)((int)hmmptr); return 0; } I don't really understand the code above, i have it from an online game - i should supply something in the arguments so it would give me shell, but i don't get it how it works so i don't know what to do. So i need someone that would explain it what it does, how it's working and the stuff. Thanks.

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  • Swig C++ Lua Pass class by reference

    - by Jeremy
    I don't know why I'm having a hard time with this. All I want to do is this: class foo { public: foo(){} ~foo(){} float a,b; }; class foo2 { public: foo2(){} foo2(const foo &f){*this = f;} ~foo2(){} void operator=(const foo& f){ x = f.a; y = f.b; } float x,y; }; /* Usage(cpp): foo f; foo2 f2(f); //or using the = operator f2 = f; */ The problem I'm having is that, after swigging this code, I can't figure out how to make the lua script play nice. /* Usage(lua) f = example.foo() f2 = example.foo2(f) --error */ The error I get is "Wrong arguments for overloaded function 'new_Foo2'": Possible c/c++ prototypes are: foo2() foo2(foo const &) The same thing happens if I try and use do f2 = f. As I understand it everything is stored as a pointer so I did try adding an additional constructor that took a pointer to foo but to no avail.

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  • Trouble with Unions in C program.

    - by Jordan S
    I am working on a C program that uses a Union. The union definition is in FILE_A header file and looks like this... // FILE_A.h**************************************************** xdata union { long position; char bytes[4]; }CurrentPosition; If I set the value of CurrentPosition.position in FILE_A.c and then call a function in FILE_B.c that uses the union, the data in the union is back to Zero. This is demonstrated below. // FILE_A.c**************************************************** int main.c(void) { CurrentPosition.position = 12345; SomeFunctionInFileB(); } // FILE_B.c**************************************************** void SomeFunctionInFileB(void) { // After the following lines execute I see all zeros in the flash memory. WriteByteToFlash(CurrentPosition.bytes[0]; WriteByteToFlash(CurrentPosition.bytes[1]; WriteByteToFlash(CurrentPosition.bytes[2]; WriteByteToFlash(CurrentPosition.bytes[3]; } Now, If I pass a long to SomeFunctionInFileB(long temp) and then store it into CurrentPosition.bytes within that function, and finally call WriteBytesToFlash(CurrentPosition.bytes[n]... it works just fine. It appears as though the CurrentPosition Union is not global. So I tried changing the union definition in the header file to include the extern keyword like this... extern xdata union { long position; char bytes[4]; }CurrentPosition; and then putting this in the source (.c) file... xdata union { long position; char bytes[4]; }CurrentPosition; but this causes a compile error that says: C:\SiLabs\Optec Programs\AgosRot\MotionControl.c:76: error 91: extern definition for 'CurrentPosition' mismatches with declaration. C:\SiLabs\Optec Programs\AgosRot\/MotionControl.h:48: error 177: previously defined here So what am I doing wrong? How do I make the union global?

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  • From where starts the process' memory space and where does it end?

    - by nhaa123
    Hi, I'm trying to dump memory from my application where the variables lye. Here's the function: void MyDump(const void *m, unsigned int n) { const unsigned char *p = reinterpret_cast<const unsigned char *(m); char buffer[16]; unsigned int mod = 0; for (unsigned int i = 0; i < n; ++i, ++mod) { if (mod % 16 == 0) { mod = 0; std::cout << " | "; for (unsigned short j = 0; j < 16; ++j) { switch (buffer[j]) { case 0xa: case 0xb: case 0xd: case 0xe: case 0xf: std::cout << " "; break; default: std::cout << buffer[j]; } } std::cout << "\n0x" << std::setfill('0') << std::setw(8) << std::hex << (long)i << " | "; } buffer[i % 16] = p[i]; std::cout << std::setw(2) << std::hex << static_cast<unsigned int(p[i]) << " "; if (i % 4 == 0 && i != 1) std::cout << " "; } } Now, how can I know from which address starts my process memory space, where all the variables are stored? And how do I now, how long the area is? For instance: MyDump(0x0000 /* <-- Starts from here? */, 0x1000 /* <-- This much? */); Best regards, nhaa123

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  • Atomic swap in GNU C++

    - by Steve
    I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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  • typename resolution in cases of ambiguity

    - by parapura rajkumar
    I was playing with Visual Studio and templates. Consider this code struct Foo { struct Bar { }; static const int Bar=42; }; template<typename T> void MyFunction() { typename T::Bar f; } int main() { MyFunction<Foo>(); return 0; } When I compile this is either Visual Studio 2008 and 11, I get the following error error C2146: syntax error : missing ';' before identifier 'f' Is Visual Studio correct in this regard ? Is the code violating any standards ? If I change the code to struct Foo { struct Bar { }; static const int Bar=42; }; void SecondFunction( const int& ) { } template<typename T> void MyFunction() { SecondFunction( T::Bar ); } int main() { MyFunction<Foo>(); return 0; } it compiles without any warnings. In Foo::BLAH a member preferred over a type in case of conflicts ?

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  • C++ Beginner Delete Question

    - by Pooch
    Hi all, This is my first year learning C++ so bear with me. I am attempting to dynamically allocate memory to the heap and then delete the allocated memory. Below is the code that is giving me a hard time: // String.cpp #include "String.h" String::String() {} String::String(char* source) { this->Size = this->GetSize(source); this->CharArray = new char[this->Size + 1]; int i = 0; for (; i < this->Size; i++) this->CharArray[i] = source[i]; this->CharArray[i] = '\0'; } int String::GetSize(const char * source) { int i = 0; for (; source[i] != '\0'; i++); return i; } String::~String() { delete[] this->CharArray; } Here is the error I get when the compiler tries to delete the CharArray: 0xC0000005: Access violation reading location 0xccccccc0. And here is the last call on the stack: msvcr100d.dll!operator delete(void * pUserData) Line 52 + 0x3 bytes C++ I am fairly certain the error exists within this piece of code but will provide you with any other information needed. Oh yeah, using VS 2010 for XP. Thanks for any and all help!

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  • Deleting a node from linked list in C

    - by LuckySlevin
    My problem is deleting a node from linked list. I have two structs : typedef struct inner_list { int count; char word[100]; inner_list*next; } inner_list; typedef struct outer_list { char word [100]; inner_list * head; int count; outer_list * next; } outer_list; My problem is in deleting a node from outer_list linked list. For example when user entered aaa to delete, delete function should find the node with outer_list->word = aaa and delete this node and reconnect the list again. I tried the below code to do this. but After finding and deleting I'm losing the list. I don't know what's wrong. Please notice that outer_list have also a linked list of inner_list inside. void delnode(outer_list *head,char num[100]) { outer_list *temp, *m; temp=head; while(temp!=NULL) { if(strcmp(temp->word==num)==0) { if(temp==head) { head=temp->next; free(temp); return; } else { m->next=temp->next; free(temp); return; } }else { m=temp; temp= temp->next; } } printf(" ELEMENT %s NOT FOUND ", num); } What are your ideas about this?

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  • C++ Switch won't compile with externally defined variable used as case

    - by C Nielsen
    I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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  • What is the purpose of the s==NULL case for mbrtowc?

    - by R..
    mbrtowc is specified to handle a NULL pointer for the s (multibyte character pointer) argument as follows: If s is a null pointer, the mbrtowc() function shall be equivalent to the call: mbrtowc(NULL, "", 1, ps) In this case, the values of the arguments pwc and n are ignored. As far as I can tell, this usage is largely useless. If ps is not storing any partially-converted character, the call will simply return 0 with no side effects. If ps is storing a partially-converted character, then since '\0' is not valid as the next byte in a multibyte sequence ('\0' can only be a string terminator), the call will return (size_t)-1 with errno==EILSEQ. and leave ps in an undefined state. The intended usage seems to have been to reset the state variable, particularly when NULL is passed for ps and the internal state has been used, analogous to mbtowc's behavior with stateful encodings, but this is not specified anywhere as far as I can tell, and it conflicts with the semantics for mbrtowc's storage of partially-converted characters (if mbrtowc were to reset state when encountering a 0 byte after a potentially-valid initial subsequence, it would be unable to detect this dangerous invalid sequence). If mbrtowc were specified to reset the state variable only when s is NULL, but not when it points to a 0 byte, a desirable state-reset behavior would be possible, but such behavior would violate the standard as written. Is this a defect in the standard? As far as I can tell, there is absolutely no way to reset the internal state (used when ps is NULL) once an illegal sequence has been encountered, and thus no correct program can use mbrtowc with ps==NULL.

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  • C++ Check Substring of a String

    - by user69514
    I'm trying to check whether or not the second argument in my program is a substring of the first argument. The problem is that it only work if the substring starts with the same letter of the string. .i.e Michigan - Mich (this works) Michigan - Mi (this works) Michigan - igan (this doesn't work) #include <stdio.h> #include <string.h> #include <string> using namespace std; bool my_strstr( string str, string sub ) { bool flag = true; int startPosition = -1; char subStart = str.at(0); char strStart; //find starting position for(int i=0; i<str.length(); i++){ if(str.at(i) == subStart){ startPosition = i; break; } } for(int i=0; i<sub.size(); i++){ if(sub.at(i) != str.at(startPosition)){ flag = false; break; } startPosition++; } return flag; } int main(int argc, char **argv){ if (argc != 3) { printf ("Usage: check <string one> <string two>\n"); } string str1 = argv[1]; string str2 = argv[2]; bool result = my_strstr(str1, str2); if(result == 1){ printf("%s is a substring of %s\n", argv[2], argv[1]); } else{ printf("%s is not a substring of %s\n", argv[2], argv[1]); } return 0; }

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