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  • how to identify process in kernel read func without using current->pid

    - by yoavstr
    my lecture wants us to build module where we need to identify each read process and where the same read process called twice on the same writer massage we should insert him to an queue who's we wake up when all readers have read I achieved this goal by by using list of pid's and boolean read/not_read inside each node but he decided to be nasty and require us to it with some argument from FILE struct can you please help me ?....

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  • Why would you avoid C++ keywords in Java?

    - by Joshua Swink
    A popular editor uses highlighting to help programmers avoid using C++ keywords in Java. The following words are displayed using the same colors as a syntax error: auto delete extern friend inline redeclared register signed sizeof struct template typedef union unsigned operator Why would this be considered important?

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  • Another void C# question

    - by Jim Jones
    Have a type in the header files I'm working with called VTVOID it is the type of a struct element and a number of parameters. In the header file defining types is the line #define VTVOID void I read in another discussion the void maps to System.Void however when I plug that into the C# code I get the error "System.Void cannot be used in C# -- use typeof(void) to get the void object." So what type do I plug in? Jim

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  • How to ensure structures are completly initialized (by name) in GCC?

    - by Steven Spark
    How do I ensure each and every field of my structures are initialized in GCC when using designated initializers? (I'm especially interested in function pointers.) (I'm using C not C++.) Here is an example: typedef struct { int a; int b; } foo_t; typedef struct { void (*Start)(void); void (*Stop)(void); } bar_t; foo_t fooo = { 5 }; foo_t food = { .b=4 }; bar_t baro = { NULL }; bar_t bard = { .Start = NULL }; -Wmissing-field-initializers does not help at all. It works for fooo only in GCC (mingw 4.7.3, 4.8.1), and clang does only marginally better (no warnings for food and bard). I'm sure there is a reason for not producing warnings for designated initializer (even when I explicitly ask for them) but I want/need them. I do not want to initialize structures based on order/position because that is more error prone (for example swapping Start and Stop won't even give any warning). And neither gcc nor clang will give any warning that I failed to explicitly initialize a field (when initializing by name). I also don't want to litter my code with if(x.y==NULL) lines for multiple reasons, one of which is I want compile time warnings and not runtime errors. At least splint will give me warnings on all 4 cases, but unfortunately I cannot use splint all the time (it chokes on some of the code (fails to parse some C99, GCC extensions)). Note: If I'm using a real function instead of NULL GCC will also show a warning for baro (but not bard). I searched google and stack overflow but only found related questions and have not found answer for this specific problem. The best match I have found is 'Ensure that all elements in a structure are initialized' Ensure that all elements in a structure are initialized Which asks pretty much the same question, but has no satisfying answer. Is there a better way dealing with this that I have not mentioned? (Maybe other code analysis tool? Preferably something (free) that can be integrated into Eclipse or Visual Studio...)

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  • [Visual C++]Forcing memory alignment of variables/data-structures

    - by John
    I'm looking at using SSE and I gather aligning data on 16byte boundaries is recommended. There are two cases to consider: float data[4]; struct myystruct { float x,y,z,w; }; I'm not sure the first case can be done explicitly, though there's perhaps a compiler option I could use? In the second case I remember being able to control packing in old versions of GCC several years back, is this still possible?

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  • access Elf section header table

    - by idealistikz
    Assume I have the following: Elf_FIle_Header *fileHeader //struct pointer, points to start of the Elf file header fileHeader->offset //byte offset from start of file to section headers Elf_Section_Header *sectionHeader = (Elf_Section_Header *)(char *)fileHeader + fileHeader->offset Why doesn't the above line point me to the start of the section header table? How do I point to the start of the section header table?

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  • Telephone Directory

    - by Mizukage of Meron 5
    I need your help. We are ask to make a telephone directory program that asks your name, address, and telephone number. If the name you entered already exists, it will display that it already exists. This is what i have so far... #include<stdio.h> #include<conio.h> struct file { char name[25],address[25]; double telno; }; char tempname[25],tempadd[25]; double tempnum; int x; int choice; FILE *fp; main() { struct file rec; clrscr(); fp=fopen("TelDir.txt","a+"); while(!feof(fp)) { fscanf(fp,"%s %s %.0lf,&tempname,&tempadd,&tempnum); printf("\n%s\t\t%s\t\t\t%.0lf",tempname,tempadd,tempnum); printf("\nEnter Name: "); gets(rec.name); if(strcmp(rec.name,tempname)==1) { printf("\n\nALREADY EXIST!"); printf("\n%s\t\t%s\t\t\t%.0lf",tempname,tempadd,tempnum); getch(); } else { printf("Enter Address: "); scanf("%s",&rec.address); printf("Enter your Telephone No.: "); scanf("%lf",&rec.telno); printf("%s\t\t%s\t\t%\t\t0lf",rec.name,rec.address,rec.telno); fprintf(fp,"%s %s %.0lf\n",rec.name,rec.address,rec.telno); } } fclose(fp); getch(); } But this thing doesn't work. I don't know where the error is. Can someone help me on this? I would really appreciate if you could help me somehow.

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  • template; Point<2, double>; Point<3, double>

    - by Oops
    Hi, I want to create my own Point struct it is only for purposes of learning C++. I have the following code: template <int dims, typename T> struct Point { T X[dims]; Point(){} Point( T X0, T X1 ) { X[0] = X0; X[1] = X1; } Point( T X0, T X1, T X2 ) { X[0] = X0; X[1] = X1; X[2] = X2; } Point<dims, int> toint() { //how to distinguish between 2D and 3D ??? Point<dims, int> ret = Point<dims, int>( (int)X[0], (int)X[1]); return ret; } std::string str(){ //how to distinguish between 2D and 3D ??? std::stringstream s; s << "{ X0: " << X[0] << " | X1: " << X[1] << " }"; return s.str(); } }; int main(void) { Point<2, double> p2d = Point<2, double>( 12.3, 45.6 ); Point<3, double> p3d = Point<3, double>( 12.3, 45.6, 78.9 ); Point<2, int> p2i = p2d.toint(); //OK Point<3, int> p3i = p3d.toint(); //m??? std::cout << p2d.str() << std::endl; //OK std::cout << p3d.str() << std::endl; //m??? std::cout << p2i.str() << std::endl; //m??? std::cout << p3i.str() << std::endl; //m??? char c; std::cin >> c; return 0; } of couse until now the output is not what I want. my questions is: how to take care of the dimensions of the Point (2D or 3D) in member functions of the Point? many thanks in advance Oops

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  • c++/boost: use tuple ctors when subclassing

    - by bbb
    Hi there, is there some way to use a boost tuple's ctors as an addition to the subclass methods (and ctors) like here? // typedef boost::tuple<int, SomeId, SomeStatus> Conn; // Conn(1); // works and initializes using default ctors of Some* struct Conn : boost::tuple<int, AsynchId, AccDevRetStatus> {}; Conn(1); // "no matching function call" (but i want it so much) T.H.X.

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  • missing subscript c++

    - by Makenshi
    right now c++ is giving me this error: error C2087 'color' missing subscript first time i get this and i dont know what to do .< hope any1 can help me struct Color{ float r; float g; float b; };Color color[][]; and im using it here for(int i=0;i<cubes;i++) { color[i][0].r = fRand();color[i][0].g=fRand(.5);color[i][0].b=fRand(); ...etc

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  • PHP text parsing and / or make your own language?

    - by AlexanderJohannesen
    Been Googling around without finding much at all, so does anyone know of a class or library that helps you parse any sort of language, like a Domain Specific Language (I'm creating one, so I'm flexible in what the syntax and format can be) into either PHP code or some helpful struct or a class hiearchy or ... ? Anything goes at this point. :) I want to experiment with parsing text files into tokens, building up a small grammar and syntax library to express things like Business Natural Languages.

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • question about a macro in Linux Kernel List implementation

    - by holydiver
    I generally have ignored using macros while writing in C but I think I know fundamentals about them. While i was reading the source code of list in linux kernel, i saw something like that: #define LIST_HEAD_INIT(name) { &(name), &(name) } #define LIST_HEAD(name) \ struct list_head name = LIST_HEAD_INIT(name) (You can access the remaining part of the code from here.) I didn't understand the function of ampersands(I don't think they are the address of operands here) in LIST_HEAD_INIT and so the use of LIST_HEAD_INIT in the code. I'd appreciate if someone can enlighten me.

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  • 'Invalid conversion from some_type** to const some_type**'

    - by petersohn
    I've got a function that requires const some_type** as an argument (some_type is a struct, and the function needs a pointer to an array of this type). I declared a local variable of type some_type*, and initialized it. Then I call the function as f(&some_array), and the compiler (gcc) says: error: invalid conversion from ‘some_type**’ to ‘const some_type**’ What's the problem here? Why can't I convert a variable to const?

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  • Why is this undefined behaviour?

    - by xryl669
    Here's the sample code: X * makeX(int index) { return new X(index); } struct Tmp { mutable int count; Tmp() : count(0) {} const X ** getX() const { static const X* x[] = { makeX(count++), makeX(count++) }; return x; } }; This reports Undefined Behaviour on CLang version 500 in the static array construction. For sake of simplication for this post, the count is not static, but it does not change anything.

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  • Go - Data types for validation

    - by nevalu
    How to create a new data type for Go which to can check/validate its schema when is created a new variable (of that type)? By example, to validate if a string has 20 characters, I tried: // Format: 2006-01-12T06:06:06Z func date(str string) { if len(str) != 20 { fmt.Println("error") } } var Date = date() type Account struct { domain string username string created Date } but it fails because Date is not a type.

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  • Flexible array member in C-structure

    - by Arpan
    Quoting from the C-std section 6.7.2.1, struct s { int n; double d[]; }; This is a valid structure declaration. I am looking for some practical use of this kind of syntax. To be precise, how is this construct any more or less powerful than keeping a double* as the 2nd element? Or is this another case of 'you-can-do-it-in-multiple-ways'? Arpan

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  • C/C++ __restrict type

    - by aaa
    hello. Is there a way to define using typedef integral/float type which implies no aliasng? something equivalent to (but primitive construct): template < typename T > struct restrict { T* __restrict data; };

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  • How does the CLR (.NET) internally allocate and pass around custom value types (structs)?

    - by stakx
    Question: Do all CLR value types, including user-defined structs, live on the evaluation stack exclusively, meaning that they will never need to be reclaimed by the garbage-collector, or are there cases where they are garbage-collected? Background: I have previously asked a question on SO about the impact that a fluent interface has on the runtime performance of a .NET application. I was particuarly worried that creating a large number of very short-lived temporary objects would negatively affect runtime performance through more frequent garbage-collection. Now it has occured to me that if I declared those temporary objects' types as struct (ie. as user-defined value types) instead of class, the garbage collector might not be involved at all if it turns out that all value types live exclusively on the evaluation stack. What I've found out so far: I did a brief experiment to see what the differences are in the CIL generated for user-defined value types and reference types. This is my C# code: struct SomeValueType { public int X; } class SomeReferenceType { public int X; } . . static void TryValueType(SomeValueType vt) { ... } static void TryReferenceType(SomeReferenceType rt) { ... } . . var vt = new SomeValueType { X = 1 }; var rt = new SomeReferenceType { X = 2 }; TryValueType(vt); TryReferenceType(rt); And this is the CIL generated for the last four lines of code: .locals init ( [0] valuetype SomeValueType vt, [1] class SomeReferenceType rt, [2] valuetype SomeValueType <>g__initLocal0, // [3] class SomeReferenceType <>g__initLocal1, // why are these generated? [4] valuetype SomeValueType CS$0$0000 // ) L_0000: ldloca.s CS$0$0000 L_0002: initobj SomeValueType // no newobj required, instance already allocated L_0008: ldloc.s CS$0$0000 L_000a: stloc.2 L_000b: ldloca.s <>g__initLocal0 L_000d: ldc.i4.1 L_000e: stfld int32 SomeValueType::X L_0013: ldloc.2 L_0014: stloc.0 L_0015: newobj instance void SomeReferenceType::.ctor() L_001a: stloc.3 L_001b: ldloc.3 L_001c: ldc.i4.2 L_001d: stfld int32 SomeReferenceType::X L_0022: ldloc.3 L_0023: stloc.1 L_0024: ldloc.0 L_0025: call void Program::TryValueType(valuetype SomeValueType) L_002a: ldloc.1 L_002b: call void Program::TryReferenceType(class SomeReferenceType) What I cannot figure out from this code is this: Where are all those local variables mentioned in the .locals block allocated? How are they allocated? How are they freed? Why are so many anonymous local variables needed and copied to-and-fro only to initialize my two local variables rt and vt?

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  • Iterating through boost ptr_vector

    - by Ockonal
    Hello, I have a ptr_vector list of my own objects. Something like this: boost::ptr_vector<SomeClass> *list; list.push_back(new SomeClass()>; ... BOOST_FOREACH(SomeClass *tempObj, list) // [x] { tempObj->... } >‘boost::ptr_vector<SomeClass>*’ is not a class, struct, or union type

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  • Binary Search Tree Contains Function

    - by Suede
    I am trying to write a "contains" function for a binary search tree. I receive the following error at compile "Unhandled exception at 0x77291CB3 (ntdll.dll) in BST.exe: 0xC00000FD: Stack overflow (parameters: 0x00000001, 0x001E2FFC)." The following is my code. struct Node { int data; Node* leftChild; Node* rightChild; Node() : leftChild(NULL), rightChild(NULL) {} }; struct BST { Node* root; BST() : root(NULL) {} void insert(int value); bool contains(int value); }; void BST::insert(int value) { Node* temp = new Node(); temp->data = value; if(root == NULL) { root = temp; return; } Node* current; current = root; Node* parent; parent = root; current = (temp->data < current->data ? (current->leftChild) : (current->rightChild) while(current != NULL) { parent = current; current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild) } if(temp->data < parent->data) { parent->leftChild = temp; } if(temp->data > parent->data) { parent->rightChild = temp; } } bool BST::contains(int value) { Node* temp = new Node(); temp->data = value; Node* current; current = root; if(temp->data == current->data) { // base case for when node with value is found std::cout << "true" << std::endl; return true; } if(current == NULL) { // base case if BST is empty or if a leaf is reached before value is found std::cout << "false" << std::endl; return false; } else { // recursive step current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild); return contains(temp->data); } } int main() { BST bst; bst.insert(5); bst.contains(4); system("pause"); } As it stands, I would insert a single node with value '5' and I would search the binary search tree for a node with value '4' - thus, I would expect the result to be false.

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  • Linux signals with extra information parameter

    - by Tester
    I was to have some extra information in the callback to sa_sigaction handler, it does not seems possible. So I was wondering if you could suggest me alternatives. Basic requirements: Function A raises an signal/event with a pointer to a struct Handler function tackles the event. The handler function would only be called on an event and a loop to wait for the event, as in select() , is undesirable. TIA

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