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  • best practice when referring to a program's name in C

    - by guest
    what is considered best practice when referring to a program's name? i've seen #define PROGRAM_NAME "myprog" printf("this is %s\n", PROGRAM_NAME); as well as printf("this is %s\n", argv[0]); i know, that the second approach will give me ./myprog rather than myprog when the program is not called from $PATH and that the first approach will guarantee consistence regarding the program's name. but is there anything else, that makes one approach superior to the other?

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  • error: expected ',' or '...' before numeric constant

    - by goldfrapp04
    Just a Qt Gui Application with QDialog as the Base Class, the simplest type you can expect. I've programmed on Qt for several times but this is the first time I meet this problem... I've added minimal code to the program, and here's the code in dialog.h (which is mostly automatically generated) #ifndef DIALOG_H #define DIALOG_H #include <QDialog> #include <QPixmap> #include "bmp.h" namespace Ui { class Dialog; } class Dialog : public QDialog { Q_OBJECT public: explicit Dialog(QWidget *parent = 0); ~Dialog(); private slots: void on_openButton_clicked(); private: Ui::Dialog *ui; BMP srcImage; QImage compressedImage[3]; }; #endif // DIALOG_H While I edit, the "public:" is underlined and says "unexpected token '('". When I try to build the program, it says in the line "Q_OBJECT", "error: expected ',' or '...' before numeric constant". I'm sure I've defined nothing related to it (to be exact, I defined an N and an n in file bmp.h, both are int). Any idea of what's wrong here? Thanks.

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  • Implementation of a C pre-processor in Python or JavaScript?

    - by grrussel
    Is there a known implementation of the C pre-processor tool implemented either in Python or JavaScript? I am looking for a way to robustly pre-process C (and C like) source code and want to be able to process, for example, conditional compilation and macros without invoking an external CPP tool or native code library. Another potential use case is pre-processing within a web application, within the web browser. So far, I have found implementations in Java, Perl, and of course, C and C again. It may be plausible to use one of the C to JavaScript compilers now becoming available. The PLY (Python Lex and Yacc) tools include a cpp implemented in Python.

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  • Is there a way to know if std::chrono::monotonic_clock is defined?

    - by Vicente Botet Escriba
    C++0X N3092 states that monotonic_clock is optional. 20.10.5.2 Class monotonic_clock [time.clock.monotonic] 1 Objects of class monotonic_clock represent clocks for which values of time_point never decrease as physical time advances. monotonic_clock may be a synonym for system_clock if system_clock::is_monotonic is true. ** 2 The class monotonic_clock is conditionally supported.** Is there a way using SFINAE or another technique to define a traits class that states if monotonic_clock is defined? struct is_monotonic_clock_defined; If yes, how? If not, shouldn't the standard define macro that gives this information at preprocessing time?

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  • Macros in C.... please give the solution

    - by Jungle_hacker
    suppose i declared a macro name anything, xyz() and now i am creating another macro xyz1() and referencing the 1st macro i.e xyz() in 2nd. finally i'll create another macro xyz2() and referencing 2nd macro in 3rd... now my question is is this correct(its executing without any problem)..? and macro xyz() is defined twice.... why its not giving error ? what is the solution..?

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  • C++: Maybe you know this fitfall?

    - by Martijn Courteaux
    Hi, I'm developing a game. I have a header GameSystem (just methods like the game loop, no class) with two variables: int mouseX and int mouseY. These are updated in my game loop. Now I want to access them from Game.cpp file (a class built by a header-file and the source-file). So, I #include "GameSystem.h" in Game.h. After doing this I get a lot of compile errors. When I remove the include he says of course: Game.cpp:33: error: ‘mouseX’ was not declared in this scope Game.cpp:34: error: ‘mouseY’ was not declared in this scope Where I want to access mouseX and mouseY. All my .h files have Header Guards, generated by Eclipse. I'm using SDL and if I remove the lines that wants to access the variables, everything compiles and run perfectly (*). I hope you can help me... This is the error-log when I #include "GameSystem.h" (All the code he is refering to works, like explained by the (*)): In file included from ../trunk/source/domein/Game.h:14, from ../trunk/source/domein/Game.cpp:8: ../trunk/source/domein/GameSystem.h:30: error: expected constructor, destructor, or type conversion before ‘*’ token ../trunk/source/domein/GameSystem.h:46: error: variable or field ‘InitGame’ declared void ../trunk/source/domein/GameSystem.h:46: error: ‘Game’ was not declared in this scope ../trunk/source/domein/GameSystem.h:46: error: ‘g’ was not declared in this scope ../trunk/source/domein/GameSystem.h:46: error: expected primary-expression before ‘char’ ../trunk/source/domein/GameSystem.h:46: error: expected primary-expression before ‘bool’ ../trunk/source/domein/FPS.h:46: warning: ‘void FPS_SleepMilliseconds(int)’ defined but not used This is the code which try to access the two variables: SDL_Rect pointer; pointer.x = mouseX; pointer.y = mouseY; pointer.w = 3; pointer.h = 3; SDL_FillRect(buffer, &pointer, 0xFF0000);

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  • C/C++ pragma in define macro

    - by aaa
    is there some way to embed pragma statement in macro with other statements? I am trying to achieve something like: #define DEFINE_DELETE_OBJECT(type) \ void delete_ ## type_(int handle); \ void delete_ ## type(int handle); \ #pragma weak delete_ ## type_ = delete_ ## type I am okay with boost solutions (save for wave) if one exists. thank you

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  • Possible to add an EventListener to a function for Actionscript 3?

    - by Tom
    I'm trying to setup something like Aspect Oriented Programming in Actionscript 3, basically the only thing I need to be able to do is something like this: SomeClass.getMethod("methodName").addEventListener(afterMethodExecuted, function() { //run code }); This way I can run code after (or before) any method in any class has run, allowing numerous new possibilities. How should I implement this?

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  • C++ Translation Phase Confusion

    - by blakecl
    Can someone explain why the following doesn't work? int main() // Tried on several recent C++ '03 compilers. { #define FOO L const wchar_t* const foo = FOO"bar"; // Will error out with something like: "identifier 'L' is undefined." #undef FOO } I thought that preprocessing was done in an earlier translation phase than string literal operations and general token translation. Wouldn't the compiler be more or less seeing this: int main() { const wchar_t* const foo = L"bar"; } It would be great if someone could cite an explanation from the standard.

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  • Problems with variadic macros in C

    - by imikedaman
    Hi, I'm having a problem with optional arguments in #define statements in C, or more specifically with gcc 4.2: bool func1(bool tmp) { return false; } void func2(bool tmp, bool tmp2) {} #define CALL(func, tmp, ...) func(tmp, ##__VA_ARGS__) int main() { // this compiles CALL(func2, CALL(func1, false), false); // this fails with: Implicit declaration of function 'CALL' CALL(func2, false, CALL(func1, false)); } That's obviously a contrived example, but does show the problem. Does anyone know how I can get the optional arguments to "resolve" correctly? Additional information: If I remove the ## before _VA_ARGS_, and do something like this: bool func2(bool tmp, bool tmp2) { return false; } #define CALL(func, tmp, ...) func(tmp, __VA_ARGS__) int main() { CALL(func2, false, CALL(func2, false, false)); } That compiles, but it no longer works with zero arguments since it would resolve to func(tmp, )

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  • Cleanest way to store lists of filter coefficients in a C header

    - by Nick T
    I have many (~100 or so) filter coefficients calculated with the aid of some Matlab and Excel that I want to dump into a C header file for general use, but I'm not sure what the best way to do this would be. I was starting out as so: #define BUTTER 1 #define BESSEL 2 #define CHEBY 3 #if FILT_TYPE == BUTTER #if FILT_ROLLOFF == 0.010 #define B0 256 #define B1 512 #define B2 256 #define A1 467 #define A2 -214 #elif FILT_ROLLOFF == 0.015 #define B0 256 #define B1 512 // and so on... However, if I do that and shove them all into a header, I need to set the conditionals (FILT_TYPE, FILT_ROLLOFF) in my source before including it, which seems kinda nasty. What's more, if I have 2+ different filters that want different roll-offs/filter types it won't work. I could #undef my 5 coefficients (A1-2, B0-2) in that coefficients file, but it still seems wrong to have to insert an #include buried in code.

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  • Where do I put all these function-like #defines, in C?

    - by Tristan
    I'm working with an embedded system, and I'm ending up with a ton of HW-interfacing #define functions. I want to put all of these into a separate file (for OOP-ness), but I don't know the best way to #include that. Do I just put them all into a .c file, then include that? Seems silly to put these in a .h file.

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  • Can I execute a "variable statements" within a function and without defines.

    - by René Nyffenegger
    I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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  • MACRO Question: Returning pointer to a certain value

    - by Andrei Ciobanu
    Is it possible to write a MACRO that has a type and a value as its input parameters (MACRO(type,value)), and returns a valid pointer to a location that holds the submitted value. This macro should perform like the following function, but in a more generic manner: int *val_to_ptr(int val){ int *r = NULL; r = nm_malloc(sizeof(*r)); *r = val; return r; } Where nm_malloc() is a failsafe malloc. The Macro usage should be compatible with this usage: printf("%d",*MACRO(int,5)); Is it possible to achieve that ?

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  • C macro issue: redefinition of functions / structure

    - by Andrei Ciobanu
    Given the following code (it's a macro that generates code for a list data structure, based on the contained type). list.h #ifndef _LIST_H #define _LIST_H #ifdef __cplusplus extern "C" { #endif #define LIST_TEMPLATE_INIT(type) \ typedef struct __list_s_##type { \ struct __list_s_##type *next; \ type value; \ } __list_##type; \ \ __list_##type * __list_##type##_malloc(type value){ \ __list_##type * list = NULL; \ list = malloc(sizeof(*list)); \ list->value = value; \ return list; \ }\ \ void __list_##type##_free(__list_##type *list){\ __list_##type * back = list;\ while(list=list->next){\ free(back);\ back = list;\ }\ } #define LIST_TYPE(type) __list_##type #define LIST_MALLOC(type,value) __list_##type##_malloc(value) #define LIST_FREE(type,list) __list_##type##_free(list) #define LIST_DATA(list) (list->value) #ifdef __cplusplus } #endif #endif /* _LIST_H */ And here is how the above code works: #include <stdio.h> #include <stdlib.h> #include "list.h" /* * */ LIST_TEMPLATE_INIT(int) int main(int argc, char** argv) { LIST_TYPE(int)* list = NULL; list = LIST_MALLOC(int, 5); printf("%d",LIST_DATA(list)); LIST_FREE(int,list); return (0); } My question, is it possible to somehow be able to call : LIST_TEMPLATE_INIT(int), as many times as I want, in a decentralized fashion ? The current issue with this right now is that calling LIST_TEMPLATE_INIT(int) in another file raise compilation errors (because of function redefinition): Example of error: error: redefinition of ‘struct __list_s_int’

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  • What is DEFAULT_CC in function declaration?

    - by humoeba
    I'm relatively new to C, and am curious what this syntax means in a function declaration: int DEFAULT_CC foo(void) where DEFAULT_CC is probably defined somewhere else as: #define DEFAULT_CC "cc" Is this a direction to use a certain compiler or something?

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  • How can I generate a list of #define values from C code?

    - by djs
    I have code that has a lot of complicated #define error codes that are not easy to decode since they are nested through several levels. Is there any elegant way I can get a list of #defines with their final numerical values (or whatever else they may be)? As an example: <header1.h> #define CREATE_ERROR_CODE(class, sc, code) ((class << 16) & (sc << 8) & code)) #define EMI_MAX 16 <header2.h> #define MI_1 EMI_MAX <header3.h> #define MODULE_ERROR_CLASS MI_1 #define MODULE_ERROR_SUBCLASS 1 #define ERROR_FOO CREATE_ERROR_CODE(MODULE_ERROR_CLASS, MODULE_ERROR_SUBCLASS, 1) I would have a large number of similar #defines matching ERROR_[\w_]+ that I'd like to enumerate so that I always have a current list of error codes that the program can output. I need the numerical value because that's all the program will print out (and no, it's not an option to print out a string instead). Suggestions for gcc or any other compiler would be helpful.

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  • How to make the first invocation of a macro different from all the next ones ?

    - by LB
    Hi, that may be really simple but i'm unable to find a good answer. How can I make a macro representing first a certain value and then a different one ? I know that's nasty but i need it to implicitly declare a variable the first time and then do nothing. This variable is required by other macros that i'm implementing. Should i leverage "argument prescan" ? thanks for the answers. EDIT To make things clearer. Suppose i have a macro FOO, and I do something like FOO FOO FOO I would like the result to be foo bar bar I don't want the actual code to be cluttered by ifndef. The programmer should only have to write macro invocations.

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  • C++ Macro problem, not replacing all values

    - by JP
    I have the following 2 macros: #define SCOPED_ENUM_HEADER(NAME) struct NAME{ enum _NAME{ #define SCOPED_ENUM_FOOTER(NAME) };}; typedef NAME::_NAME NAMEtype; Only the first instance of NAME get replaced by the passed NAME. What's wrong with it? Is is to be used in such a way: SCOPED_ENUM_HEADER(LOGLEVEL) UNSET, FILE, SCREEN SCOPED_ENUM_FOOTER(LOGLEVEL) Thanks you

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