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• setup Qt and PyQt on mac osx so my app can also deployable on windows

  - by hk_programmer

  Hi, I've been coding with Python and C++ and now need to work on building a gui for data visualization purposes. I work on Mac Snow Leopard (intel), python 3.1 using gcc 4.2.1 (from Xcode 3.1) I wanted to first install Qt and then PyQt. And my goals are to be able to: - quickly prototype GUI and the accompanied logic that drives the GUI using PyQt and python - if I decided I need the speed, or if it's fairly easy to translate my GUI into C++ using the Qt tools, I have the options to translate my app into C++ - Be able to deploy my application onto Windows (both the python and c++ version of my app) Give the goals above, what are the correct steps I should take and what issues i should be aware of when setting up Qt and PyQt. Which other deployment tools do I need? From my readings so far, here's what I have: download the Qt source for mac and configure it with -platform macx-g++42 -arch x86_64 -no-framework (i've read somewhere that building as framework causes some trouble in deployment and/or debugging, can't find the article anymore) download latest SIP source and build download latest PyQt and build from source (any special options I should pay attention to?) For deployment, I've read that I would need to use py2exe/cx_freeze for windows, p2app for mac: http://arstechnica.com/open-source/guides/2009/03/how-to-deploying-pyqt-applications-on-windows-and-mac-os-x.ars but seems like what the article describe is deploying an app you build on windows on the windows platform and vice versa. How do you deploy to windows (is it even possible?) if you are writing your Qt app on a mac ? Really appreciate the help

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• A public struct inside a class

  - by Koning Baard

  I am new to C++, and let's say I have two classes: Creature and Human: /* creature.h */ class Creature { private: public: struct emotion { /* All emotions are percentages */ char joy; char trust; char fear; char surprise; char sadness; char disgust; char anger; char anticipation; char love; }; }; /* human.h */ class Human : Creature { }; And I have this in my main function in main.cpp: Human foo; My question is: how can I set foo's emotions? I tried this: foo->emotion.fear = 5; But GCC gives me this compile error: error: base operand of '-' has non-pointer type 'Human' This: foo.emotion.fear = 5; Gives: error: 'struct Creature::emotion' is inaccessible error: within this context error: invalid use of 'struct Creature::emotion' Can anyone help me? Thanks P.S. No I did not forget the #includes

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• char[] and char* compatibility?

  - by Aerovistae

  In essence, will this code work? And before you say "Run it and see!", I just realized my cygwin didn't come with gcc and it's currently 40 minutes away from completing reinstallation. That being said: char* words[1000]; for(int i = 0; i<1000; i++) words[i] = NULL; char buffer[ 1024 ]; //omit code that places "ADD splash\0" into the buffer if(strncmp (buffer, "ADD ", 4){ char* temp = buffer + 4; printf("Adding: %s", temp); int i = 0; while(words[i] != NULL) i++; words[i] = temp; } I'm mostly uncertain about the line char* temp = buffer + 4, and also whether I can assign words[i] in the manner that I am. Am I going to get type errors when I eventually try to compile this in 40 minutes? Also-- if this works, why don't I need to use malloc() on each element of words[]? Why can I say words[i] = temp, instead of needing to allocate memory for words[i] the length of temp?

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• C++ compilers and back/front ends

  - by aaa

  Hello. for my own education I am curious what compilers use which C++ front-end and backend. Can you enlighten me where the following technologies are used and what hallmarks/advantages they have if any? Open64 - is it backend, front-end, or both? Which compilers use it? I encounter it in cuda compiler. EDG - as far as I can tell this is a backend use by Intel compilers and Comeau. do other compilers use it? I found quite a few references to it in boost source code. ANTLR - this is general parser. Do any common compilers use it? Regarding compilers: with front-end/backend does gcc compiler suite uses? does it have common heritage with any other compiler? what front-end/backend PGI and PathScale compilers use? what front-end/backend XL compiler uses (IBM offering). Thanks.

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• Memory allocation for a matrix in C

  - by Snogzvwtr

  Why is the following code resulting in Segmentation fault? (I'm trying to create two matrices of the same size, one with static and the other with dynamic allocation) #include <stdio.h> #include <stdlib.h> //Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } Weirdly enough, if I comment out one of the matrix definitions, the code runs fine. Like this: #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; //int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } or #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; //int** b = (int**) malloc(sizeof(int*) * X); //for(i=0; i<X; i++){ // b[i] = malloc (sizeof(int) * Y); //} } I'm running gcc on Linux on a 32-bit machine.

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• Pointers and Addresses in C

  - by Mohit

  #include "stdio.h" main() { int i=3,*x; float j=1.5,*y; char k='c',*z; x=&i; y=&j; z=&k; printf("\nAddress of x= %u",x); printf("\nAddress of y= %u",y); printf("\nAddress of z= %u",z); x++; y++;y++;y++;y++; z++; printf("\nNew Address of x= %u",x); printf("\nNew Address of y= %u",y); printf("\nNew Address of z= %u",z); printf("\nNew Value of i= %d",i); printf("\nNew Value of j= %f",j); printf("\nNew Value of k= %c\n",k); } Output: Address of x= 3219901868 Address of y= 3219901860 Address of z= 3219901875 New Address of x= 3219901872 New Address of y= 3219901876 New Address of z= 3219901876 New Value of i= 3 New Value of j= 1.500000 New Value of k= c The new address of variable y and z are same. How can two variables have same address and et have different values? Note: I used gcc compiler on Ubuntu 9.04

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• Static libraries in version-cross-compiled program

  - by Brian Postow

  I have a unix command line app (with big nasty makefile) that I'm trying to run on a mac. I am compiling it on a 10.6 system, with all of the appropriate libraries of course. The deployment environment is a 10.5 system, with no extra libraries. I compiled without -dynamic, and it appears to have static libraries, correctly. When I run it on the 10.6 system, it works. However, when I run it on the 10.5 system, I get: dyld: unknown required load command 0x80000022 I got this same error when I compiled things for the 10.6 system using the 10.5 xcode, so it looks like a version mis-match type problem. However, I used gcc-4.0, and $CFLAGS = -isysroot /Developer/SDKs/MacOSX10.5.sdk -mmacosx-version-min=10.5 so it SHOULD be set up for 10.5... any ideas? thanks Editing an ancient question: I have the exact same problem on a different computer. This time I am at 10.5.8, fully update, the same executable works on 10.6 still. Has anyone had any luck with this in the months since I asked this?

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• Template Child Class Overriding a Parent Class's Virtual Function

  - by user334066

  The below code compiles with gcc v4.3.3 and the templated child class seems to be overriding a virtual function in the parent, but doesn't that break the rule that you cannot have a virtual template function? Or is something else happening that I don't understand? class BaseClass { public: virtual void Func(int var) { std::cout<<"Base int "<<var<<std::endl; } virtual void Func(double var) { std::cout<<"Base double "<<var<<std::endl; } }; template <class TT> class TemplateClass : public BaseClass { public: using BaseClass::Func; virtual void Func(TT var) { std::cout<<"Child TT "<<var<<std::endl; } }; int main(int argc, char **argv) { BaseClass a; TemplateClass<int> b; BaseClass *c = new TemplateClass<int>; int intVar = 3; double doubleVar = 5.5; a.Func(intVar); a.Func(doubleVar); b.Func(intVar); b.Func(doubleVar); c->Func(intVar); c->Func(doubleVar); delete c; } This then outputs: Base int 3 Base double 5.5 Child TT 3 Base double 5.5 Child TT 3 Base double 5.5 as I hoped, but I'm not sure why it works.

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• Why is passing a string literal into a char* argument only sometimes a compiler error?

  - by Brian Postow

  I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0. EDIT: added code: char * host = FindArgDefault("EMailLinkHost", ""); stripCRLF(linkHost, '\n'); where: char *FindArgDefault(char *argName, char *defVal) {// simplified char * val = defVal; return(val); } and void stripCRLF(char *str, char delim) { char *p, *q; for (p = q = str; *p; ++p) { if (*p == 0xd || *p == 0xa) { if (p[1] == (*p ^ 7)) ++p; if (delim == -1) *p = delim; } *q++ = *p; } *q = 0; // DIES HERE } This compiled and ran until it tried to set *q to 0...

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• Howcome some C++ functions with unspecified linkage build with C linkage?

  - by christoffer

  This is something that makes me fairly perplexed. I have a C++ file that implements a set of functions, and a header file that defines prototypes for them. When building with Visual Studio or MingW-gcc, I get linking errors on two of the functions, and adding an 'extern "C"' qualifier resolved the error. How is this possible? Header file, "some_header.h": // Definition of struct DEMO_GLOBAL_DATA omitted DWORD WINAPI ThreadFunction(LPVOID lpData); void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen); void CheckValid(DEMO_GLOBAL_DATA *pData); int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName); void HandleEnd(DEMO_GLOBAL_DATA *pData); C++ file, "some_implementation.cpp" #include "some_header.h" DWORD WINAPI ThreadFunction(LPVOID lpData) { /* omitted */ } void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen) { /* omitted */ } void CheckValid(DEMO_GLOBAL_DATA *pData) { /* omitted */ } int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName) { /* omitted */ } void HandleEnd(DEMO_GLOBAL_DATA *pData) { /* omitted */ } The implementations compile without warnings, but when linking with the UI code that calls these, I get a normal error LNK2001: unresolved external symbol "int __cdecl HandleStart(struct _DEMO_GLOBAL_DATA *, wchar_t *) error LNK2001: unresolved external symbol "void __cdecl CheckValid(struct _DEMO_MAIN_GLOBAL_DATA * What really confuses me, now, is that only these two functions (HandleStart and CheckValid) seems to be built with C linkage. Explicitly adding "extern 'C'" declarations for only these two resolved the linking error, and the application builds and runs. Adding "extern 'C'" on some other function, such as HandleEnd, introduces a new linking error, so that one is obviously compiled correctly. The implementation file is never modified in any of this, only the prototypes.

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• typedef struct, circular dependency, forward definitions

  - by BlueChip

  The problem I have is a circular dependency issue in C header files ...Having looked around I suspect the solution will have something to do with Forward Definitions, but although there are many similar problems listed, none seem to offer the information I require to resolve this one... I have the following 5 source files: // fwd1.h #ifndef __FWD1_H #define __FWD1_H #include "fwd2.h" typedef struct Fwd1 { Fwd2 *f; } Fwd1; void fwd1 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD1_H . // fwd1.c #include "fwd1.h" #include "fwd2.h" void fwd1 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwd2.h #ifndef __FWD2_H #define __FWD2_H #include "fwd1.h" typedef struct Fwd2 { Fwd1 *f; } Fwd2; void fwd2 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD2_H . // fwd2.c #include "fwd1.h" #include "fwd2.h" void fwd2 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwdMain.c #include "fwd1.h" #include "fwd2.h" int main (int argc, char** argv, char** env) { Fwd1 *f1 = (Fwd1*)0; Fwd2 *f2 = (Fwd2*)0; fwd1(f1, f2); fwd2(f1, f2); return 0; } Which I am compiling with the command: gcc fwdMain.c fwd1.c fwd2.c -o fwd -Wall I have tried several ideas to resolve the compile errors, but have only managed to replace the errors with other errors ...How do I resolve the circular dependency issue with the least changes to my code? ...Ideally, as a matter of coding style, I would like to avoid putting the word "struct" all over my code.

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• C++ template member specialization - is this a compiler limitation?

  - by LoudNPossiblyRight

  Is it possible to do this kind of specialization? If so, how? The specialization in question is marked //THIS SPECIALIZATION WILL NOT COMPILE I have used VS2008, VS2010, gcc 4.4.3 and neither can compile this. #include<iostream> #include<string> using namespace std; template <typename ALPHA> class klass{ public: template <typename BETA> void func(BETA B); }; template <typename ALPHA> template <typename BETA> void klass<ALPHA>::func(BETA B){ cout << "I AM A BETA FUNC: " << B <<endl; } //THIS SPECIALIZATION WILL NOT COMPILE template <typename ALPHA> template <> void klass<ALPHA>::func(string B){ cout << "I AM A SPECIAL BETA FUNC: " << B <<endl; } int main(){ klass<string> k; k.func(1); k.func("hello"); return 0; }

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• C++ iterator and const_iterator problem for own container class

  - by BaCh

  Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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• Using an initializer_list on a map of vectors

  - by Hooked

  I've been trying to initialize a map of <ints, vector<ints> > using the new 0X standard, but I cannot seem to get the syntax correct. I'd like to make a map with a single entry with key:value = 1:<3,4 #include <initializer_list> #include <map> #include <vector> using namespace std; map<int, vector<int> > A = {1,{3,4}}; .... It dies with the following error using gcc 4.4.3: error: no matching function for call to std::map<int,std::vector<int,std::allocator<int> >,std::less<int>,std::allocator<std::pair<const int,std::vector<int,std::allocator<int> > > > >::map(<brace-enclosed initializer list>) Edit Following the suggestion by Cogwheel and adding the extra brace it now compiles with a warning that can be gotten rid of using the -fno-deduce-init-list flag. Is there any danger in doing so?

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• null terminating a string

  - by robUK

  Hello, gcc 4.4.4 c89 just wondering what is the standard way to null terminate a string. i.e. However, when I use the NULL I get the warning message. *dest++ = 0; *dest++ = '\0'; *dest++ = NULL; /* Warning: Assignment takes integer from pointer without a cast */ source code I am using: size_t s_strscpy(char *dest, const char *src, const size_t len) { /* Copy the contents from src to dest */ size_t i = 0; for(i = 0; i < len; i++) *dest++ = *src++; /* Null terminate dest */ *dest++ = 0; return i; } Just another quick question. I deliberately commented out the line that null terminates. However, it still correctly printed out the contents of the dest. The caller of this function would send the length of the string by either included the NULL or not. i.e. strlen(src) + 1 or stlen(src). size_t s_strscpy(char *dest, const char *src, const size_t len) { /* Copy the contents from src to dest */ size_t i = 0; /* Don't copy the null terminator */ for(i = 0; i < len - 1; i++) *dest++ = *src++; /* Don't add the Null terminator */ /* *dest++ = 0; */ return i; } Many thanks for any advice,

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• Segmentation fault on returning from main (very short and simple code, no arrays or pointers)

  - by Gábor Kovács

  I've been wondering why the following trivial code produces a segmentation fault when returning from main(): //Produces "Error while dumping state (probably corrupted stack); Segmentation fault" #include <iostream> #include <fstream> #include <vector> using namespace std; class Test { vector<int> numbers; }; int main() { Test a; ifstream infile; cout << "Last statement..." << endl; // this gets executed return 0; } Interestingly, 1) if only one of the two variables is declared, I don't get the error, 2) if I declare a vector variable instead of an object with a vector member, everything's fine, 3) if I declare an ofstream instead of an ifstream, again, everything works fine. Something appears to be wrong with this specific combination... Could this be a compiler bug? I use gcc version 3.4.4 with cygwin. Thanks for the tips in advance. Gábor

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• Inline function v. Macro in C -- What's the Overhead (Memory/Speed)?

  - by Jason R. Mick

  I searched Stack Overflow for the pros/cons of function-like macros v. inline functions. I found the following discussion: Pros and Cons of Different macro function / inline methods in C ...but it didn't answer my primary burning question. Namely, what is the overhead in c of using a macro function (with variables, possibly other function calls) v. an inline function, in terms of memory usage and execution speed? Are there any compiler-dependent differences in overhead? I have both icc and gcc at my disposal. My code snippet I'm modularizing is: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = AttractiveTerm * AttractiveTerm; EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); My reason for turning it into an inline function/macro is so I can drop it into a c file and then conditionally compile other similar, but slightly different functions/macros. e.g.: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = pow(SigmaSquared/RadialDistanceSquared,9); EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); (note the difference in the second line...) This function is a central one to my code and gets called thousands of times per step in my program and my program performs millions of steps. Thus I want to have the LEAST overhead possible, hence why I'm wasting time worrying about the overhead of inlining v. transforming the code into a macro. Based on the prior discussion I already realize other pros/cons (type independence and resulting errors from that) of macros... but what I want to know most, and don't currently know is the PERFORMANCE. I know some of you C veterans will have some great insight for me!!

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• User Defined Conversions in C++

  - by wash

  Recently, I was browsing through my copy of the C++ Pocket Reference from O'Reilly Media, and I was surprised when I came across a brief section and example regarding user-defined conversion for user-defined types: #include <iostream> class account { private: double balance; public: account (double b) { balance = b; } operator double (void) { return balance; } }; int main (void) { account acc(100.0); double balance = acc; std::cout << balance << std::endl; return 0; } I've been programming in C++ for awhile, and this is the first time I've ever seen this sort of operator overloading. The book's description of this subject is somewhat brief, leaving me with a few unanswered questions about this feature: Is this a particularly obscure feature? As I said, I've been programming in C++ for awhile and this is the first time I've ever come across this. I haven't had much luck finding more in-depth material regarding this. Is this relatively portable? (I'm compiling on GCC 4.1) Can user-defined conversions to user defined types be done? e.g. operator std::string () { /* code */ }

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• Can g++ fill uninitialized POD variables with known values?

  - by Bob Lied

  I know that Visual Studio under debugging options will fill memory with a known value. Does g++ (any version, but gcc 4.1.2 is most interesting) have any options that would fill an uninitialized local POD structure with recognizable values? struct something{ int a; int b; }; void foo() { something uninitialized; bar(uninitialized.b); } I expect uninitialized.b to be unpredictable randomness; clearly a bug and easily found if optimization and warnings are turned on. But compiled with -g only, no warning. A colleague had a case where code similar to this worked because it coincidentally had a valid value; when the compiler upgraded, it started failing. He thought it was because the new compiler was inserting known values into the structure (much the way that VS fills 0xCC). In my own experience, it was just different random values that didn't happen to be valid. But now I'm curious -- is there any setting of g++ that would make it fill memory that the standard would otherwise say should be uninitialized?

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• How can I avoid encoding mixups of strings in a C/C++ API?

  - by Frerich Raabe

  I'm working on implementing different APIs in C and C++ and wondered what techniques are available for avoiding that clients get the encoding wrong when receiving strings from the framework or passing them back. For instance, imagine a simple plugin API in C++ which customers can implement to influence translations. It might feature a function like this: const char *getTranslatedWord( const char *englishWord ); Now, let's say that I'd like to enforce that all strings are passed as UTF-8. Of course I'd document this requirement, but I'd like the compiler to enforce the right encoding, maybe by using dedicated types. For instance, something like this: class Word { public: static Word fromUtf8( const char *data ) { return Word( data ); } const char *toUtf8() { return m_data; } private: Word( const char *data ) : m_data( data ) { } const char *m_data; }; I could now use this specialized type in the API: Word getTranslatedWord( const Word &englishWord ); Unfortunately, it's easy to make this very inefficient. The Word class lacks proper copy constructors, assignment operators etc.. and I'd like to avoid unnecessary copying of data as much as possible. Also, I see the danger that Word gets extended with more and more utility functions (like length or fromLatin1 or substr etc.) and I'd rather not write Yet Another String Class. I just want a little container which avoids accidental encoding mixups. I wonder whether anybody else has some experience with this and can share some useful techniques. EDIT: In my particular case, the API is used on Windows and Linux using MSVC 6 - MSVC 10 on Windows and gcc 3 & 4 on Linux.

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• C program - Seg fault, cause of

  - by resonant_fractal

  Running this gives me a seg fault (gcc filename.c -lm), when i enter 6 (int) as a value. Please help me get my head around this. The intended functionality has not yet been implemented, but I need to know why I'm headed into seg faults already. Thanks! #include<stdio.h> #include<math.h> int main (void) { int l = 5; int n, i, tmp, index; char * s[] = {"Sheldon", "Leonard", "Penny", "Raj", "Howard"}; scanf("%d", &n); //Solve Sigma(Ai*2^(i-1)) = (n - k)/l if (n/l <= 1) printf("%s\n", s[n-1]); else { tmp = n; for (i = 1;;) { tmp = tmp - (l * pow(2,i-1)); if (tmp <= 5) { // printf("Breaking\n"); break; } ++i; } printf("Last index = %d\n", i); // ***NOTE*** //Value lies in next array, therefore ++i; index = tmp + pow(2, n-1); printf("%d\n", index); } return 0; }

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• Why doesn't g++ pay attention to __attribute__((pure)) for virtual functions?

  - by jchl

  According to the GCC documentation, __attribute__((pure)) tells the compiler that a function has no side-effects, and so it can be subject to common subexpression elimination. This attribute appears to work for non-virtual functions, but not for virtual functions. For example, consider the following code: extern void f( int ); class C { public: int a1(); int a2() __attribute__((pure)); virtual int b1(); virtual int b2() __attribute__((pure)); }; void test_a1( C *c ) { if( c->a1() ) { f( c->a1() ); } } void test_a2( C *c ) { if( c->a2() ) { f( c->a2() ); } } void test_b1( C *c ) { if( c->b1() ) { f( c->b1() ); } } void test_b2( C *c ) { if( c->b2() ) { f( c->b2() ); } } When compiled with optimization enabled (either -O2 or -Os), test_a2() only calls C::a2() once, but test_b2() calls b2() twice. Is there a reason for this? Is it because, even though the implementation in class C is pure, g++ can't assume that the implementation in every subclass will also be pure? If so, is there a way to tell g++ that this virtual function and every subclass's implementation will be pure?

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• complete nub.. iostream file not found

  - by user1742389

  folks I am almost completely new to programming so please bear with me. I am using the first example from lydia.com c++ videos and failing. I am using Xcode 4.5.1 with a c++ command line project instead of eclipse and I am getting an error on compile of iostream file not found. the code is simple and I will include exactly what I have at the end of this message. I thought that iostream was a standard header that came with all even remotely recent versions of c++ compilers and am shocked to get this error and I cannot find any way to fix this. please tell me whats going on. #include <iostream> #include <stdio.h> #include <sstream> #include <vector> int main(int argc, char ** argv) { stringstream version; version << "GCC Version"; _GNUC_<<"."<<_GNUC_MINOR_<<"."<<_GNUC_PATCHLEVEL_<<_"\nVersion String: " <<_VERSION_; cout <<version.string() endl; vector<string> v={"one","two","three"}; for ( s : v ) { cout << s <<endl; } // insert code here... printf("Hello, World!\n"); return 0; } Thanks.

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• What new Unicode functions are there in C++0x?

  - by luiscubal

  It has been mentioned in several sources that C++0x will include better language-level support for Unicode(including types and literals). If the language is going to add these new features, it's only natural to assume that the standard library will as well. However, I am currently unable to find any references to the new standard library. I expected to find out the answer for these answers: Does the new library provide standard methods to convert UTF-8 to UTF-16, etc.? Does the new library allowing writing UTF-8 to files, to the console (or from files, from the console). If so, can we use cout or will we need something else? Does the new library include "basic" functionality such as: discovering the byte count and length of a UTF-8 string, converting to upper-case/lower-case(does this consider the influence of locales?) Finally, are any of these functions are available in any popular compilers such as GCC or Visual Studio? I have tried to look for information, but I can't seem to find anything? I am actually starting to think that maybe these things aren't even decided yet(I am aware that C++0x is a work in progress).

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• Guru of the Week 2 no match for the operator==

  - by Adam

  From Guru of the Week 2. We have the function: string FindAddr(const list<Employee> l, string name) { for( list<Employee>::const_iterator i = l.begin(); i != l.end(); i++) { if( *i == name ) // here will be compilation error { return (*i).addr; } } return ""; } I added dummy Employee class to that: class Employee { string n; public: string addr; Employee(string name) : n(name) {} Employee() {} string name() const { return n; } operator string() { return n; } }; And got compilation error: error: no match for ‘operator==’ in ‘i.std::_List_iterator<_Tp>::operator* [with _Tp = Employee]() == name’ It works only if add operator== to Employee. But, Herb Sutter wrote that: The Employee class isn't shown, but for this to work it must either have a conversion to string or a conversion ctor taking a string. But Employee has a conversion function and conversion constructor as well. GCC version 4.4.3. Compiled normally, g++ file.cpp without any flags. There should be implicit conversion and it should work, why it doesn't?

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