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  • What is wrong with this c strdup code?

    - by bstullkid
    Consider this code: char *strs[] = { "string1", "string2", NULL }; char *ptr1 = NULL, *ptr2 = NULL, *tmp; short iter = 0; tmp = ptr1; while (iter < 2) { tmp = strdup(strs[iter]); tmp = ptr2; iter++; } printf("1: %s\n2: %s\n", ptr1, ptr2); I want this to output "string1\nstring2\n" however str1 and str2 remain null. What am I doing wrong?

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  • function in c language

    - by sandy101
    Hello, I am practice the function in c and come across to the program .... include int main() { float a=15.5; char ch ='C'; printit(a,ch); return 0; } printit(a,ch) { printf("%f\n%c",a,ch); } I want to know that why the above program compile and not give the error as i understood so for is ... 1) The function in c must be declared with the specific prototype (but this program does not contain the prototype ) 2)why the program give the output 'x'for the char variable 3)can the function in c are capable of accepting the value without being declared about type in parameters like what has done in the function declaration .... plz.... help

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  • How to call operator<< on "this" in a descendant of std::stringstream?

    - by romkyns
    class mystream : public std::stringstream { public: void write_something() { this << "something"; } }; This results in the following two compile errors on VC++10: error C2297: '<<' : illegal, right operand has type 'const char [10]' error C2296: '<<' : illegal, left operand has type 'mystream *const ' Judging from the second one, this is because what this points at can't be changed, but the << operator does (or at least is declared as if it does). Correct? Is there some other way I can still use the << and >> operators on this?

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  • PHP , What is the difference between fopen r+ and r ! does it matter if i used r+ when not intending

    - by Naughty.Coder
    when I use fopen function , why don't I use r+ always , even when I'm not going to write any thing ... is there a reason for separating writing/reading process from only reading .. like , the file is locked for reading when I use r+ , because i might write new data into it or something ... another question : in php manual a+ : Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it. What is supposed to be read if you are at the end of the file ..(pointer at the end) !!? where to learn more about the filesystem thing .... it's confusing

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  • ASP/HTML problem with spaces and monofonts

    - by nickik
    I have a ASP has a Function that converts ä to &auml so far so good. I have lets say space for 10 char's if there are more cut them of if there are less fill the space up with &nbsp's. . Like this: test &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp but if i say "täst" it does this: te &auml t &nbsp It interprets the &auml not as one char it looks at it as 6 chars. Is there a clever way around that? This problem messes up my design because I need the right count of spaces. The whole thing goes into a big select box. Of you have to add a ; at the end of ever &... I could add them because the Editor would really interprt them.

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  • new operator overwriting an existing object

    - by dvpdiner2
    I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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  • Passing arguments to UILabel [ 2 ] *

    - by DesperateLearner
    I'm trying to call a method of the below (Scroll animation class) type from a viewcontroller class. -(void)CreateLabel:(CGRect )frame andLabel:(UILabel *[NUM_LABELS])label andview:(UIView *)view; I got some errors when I tried passing the argument. Any suggestion on how to call this? This is how I called that method ScrollAnimation *newAnimation = [[ScrollAnimation alloc] init]; [newAnimation CreateLabel:CGRectMake(0, 50, 300,30) andLabel:animateLabel[NUM_LABELS] andview:self.view]; I have the error /Volumes/Red Drive/CarTransition/CarTransition/ViewController.m:120:66: Implicit conversion of an Objective-C pointer to 'UILabel **' is disallowed with ARC /Volumes/Red Drive/CarTransition/CarTransition/ViewController.m:120:66: Incompatible pointer types sending 'UILabel *__strong' to parameter of type 'UILabel **'

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  • Referencing invalid memory locations with C++ Iterators

    - by themoondothshine
    I am a big fan of GCC, but recently I noticed a vague anomaly. Using __gnu_cxx::__normal_iterator (ie, the most common iterator type used in libstdc++, the C++ STL) it is possible to refer to an arbitrary memory location and even change its value without causing an exception! Is this expected behavior? If so, isn't a security loophole? Here's an example: #include <iostream> using namespace std; int main() { basic_string<char> str("Hello world!"); basic_string<char>::iterator iter = str.end(); iter += str.capacity() + 99999; *iter = 'x'; cout << "Value: " << *iter << endl; }

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  • C++: Vector3 type "wall" ?

    - by anon
    Say I have: class Vector3 { float x, y, z; ... bunch of cuntions .. static operator+(const Vector3&, const Vector3); }; Now, suppose I want to have classes: Position, Velocity, that are exactly like Vector3 (basically, I want typedef Vector3 Position; typedef Vector3 Velocity; Except, given: Position position; Vector3 vector3; Velocity velocity; I want to make sure the following can't happen: position + vector3; vector3 + velocity; velocity + position; What is the best way to achieve this?

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  • parsing command option with default values and range constrains in C

    - by agramfort
    Hi, I need to parse command line arguments in C. My arguments are basically int or float with default values and range constrains. I've started to implement something that look like this: option_float(float* out, int argc, char* argv, char* name, description, float default_val, int is_optional, float min_value, float max_value) which I call for example with: float* pct; option_float(pct, argc, argv, "pct", "My super percentage option", 50, 1, FALSE, 0, 100) however I don't want to reinvent the wheel ! My objective is to have error checking of range constrains, throw an error when the option is not optional and is not set. And generate the help message usually given by usage() function. The usage text would look like this: --pct My super percentage option (default : 50). Should be in [0, 100] I've started with getopt but it is too limited for what I want to do and I feel it still requires me to write too much code for a simple usecase like this. thanks

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  • How do I compare vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • How do you detach an array of strings from shared memory? C

    - by Tim
    I have: int array_id; char* records[10]; // get the shared segment if ((array_id = shmget(IPC_PRIVATE, 1, 0666)) == -1) { perror("Array Creating"); } // attach records[0] = (char*) shmat(array_id, (void*)0, 0); if ((int) *records == -1) { perror("Array Attachment"); } which works fine, but when i try and detach i get an "invalid argument" error. // detach int error; if( (error = shmdt((void*) records[0])) == -1) { perror(array detachment); } any ideas? thank you

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  • Solving C++ 'target of assignment not really an lvalue' errors

    - by Jason
    Given this code: void FrMemCopy(void *to, const void *from, size_t sz) { size_t sz8 = sz >> 3; size_t sz1 = sz - (sz8 << 3); while (sz8-- != 0) { *((double *)to)++ = *((double *)from)++; } while (sz1-- != 0) { *((char *)to)++ = *((char *)from)++; } } I am receiving target of assignment not really an lvalue warnings on the 2 lines inside the while loops. Can anyone break down those lines? a cast then an increment? What is a simplier way to write that? What does the error mean?

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  • g++ no matching function call error

    - by gufftan
    I've got a compiler error but I can't figure out why. the .hpp: #ifndef _CGERADE_HPP #define _CGERADE_HPP #include "CVektor.hpp" #include <string> class CGerade { protected: CVektor o, rv; public: CGerade(CVektor n_o, CVektor n_rv); CVektor getPoint(float t); string toString(); }; the .cpp: #include "CGerade.hpp" CGerade::CGerade(CVektor n_o, CVektor n_rv) { o = n_o; rv = n_rv.getUnitVector(); } the error message: CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&) CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&)

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  • Objective-C: how to splt a string constant across multiple lines

    - by Ilya
    Hi, I have a pretty long sqlite query: const char *sql_query = "SELECT statuses.word_id FROM lang1_words, statuses WHERE statuses.word_id = lang1_words.word_id ORDER BY lang1_words.word ASC"; How can I break it in a number of lines to make it easier to read? If I do the following: const char *sql_query = "SELECT word_id FROM table1, table2 WHERE table2.word_id = table1.word_id ORDER BY table1.word ASC"; I am getting a error. Is there a way to write queries in multiple lines? Thank you.

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  • Flex, continuous scanning stream (from socket). Did I miss something using yywrap()?

    - by Diederich Kroeske
    Working on a socketbased scanner (continuous stream) using Flex for pattern recognition. Flex doesn't find a match that overlaps 'array bounderies'. So I implemented yywrap() to setup new array content as soon yylex() detects < (it will call yywrap). No success so far. Basically (for pin-pointing my problem) this is my code: %{ #include <stdio.h> #include <string.h> #include <stdlib.h> #define BUFFERSIZE 26 /* 0123456789012345678901234 */ char cbuf1[BUFFERSIZE] = "Hello everybody, lex is su"; // Warning, no '\0' char cbuf2[BUFFERSIZE] = "per cool. Thanks! "; char recvBuffer[BUFFERSIZE]; int packetCnt = 0; YY_BUFFER_STATE bufferState1, bufferState2; %} %option nounput %option noinput %% "super" { ECHO; } . { printf( "%c", yytext[0] );} %% int yywrap() { int retval = 1; printf(">> yywrap()\n"); if( packetCnt <= 0 ) // Stop after 2 { // Copy cbuf2 into recvBuffer memcpy(recvBuffer, cbuf2, BUFFERSIZE); // yyrestart(NULL); // ?? has no effect // Feed new data to flex bufferState2 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // packetCnt++; // Tell flex to resume scanning retval = 0; } return(retval); } int main(void) { printf("Lenght: %d\n", (int)sizeof(recvBuffer)) ; // Copy cbuf1 into recvBuffer memcpy(recvBuffer, cbuf1, BUFFERSIZE); // packetCnt = 0; // bufferState1 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // yylex(); yy_delete_buffer(bufferState1); yy_delete_buffer(bufferState2); return 0; } This is my output: dkmbpro:test dkroeske$ ./text Lenght: 26 Hello everybody, lex is su>> yywrap() per cool. Thanks! >> yywrap() So no match on 'super'. According to the doc the lexxer is not 'reset' between yywrap's. What do I miss? Thanks.

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  • Perl : How to print all cp1252 characters on by one ?

    - by Vinay
    Hi,i am not able to write a script to print all the latin -1 characters one by one.Can anybody help me in solving the problem? I am using the below code but it is not giving me expected result. foreach $char(0..255) { $hexval = sprintf("%x",$char); $charval = sprintf("%c",%hexval); print "$charval"; } output should be like :- 0065 - e 0066 - f ... ... 007F - character at the step For all the codepoints after 007F,it is not giving me expected results. Please help me out with this

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  • How to check whether iterators form a contiguous memory zone?

    - by Vincent
    I currently have the following function to read an array or a vector of raw data (_readStream is a std::ifstream) : template<typename IteratorType> inline bool MyClass::readRawData( const IteratorType& first, const IteratorType& last, typename std::iterator_traits<IteratorType>::iterator_category* = nullptr ) { _readStream.read(reinterpret_cast<char*>(&*first), (last-first)*sizeof(*first)); return _readStream.good(); } First question : does this function seem ok for you ? As we read directly a block of memory, it will only work if the memory block from first to last is contiguous in memory. How to check that ?

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  • How is push()ing and pop()ping defined?

    - by Helper Method
    I know how the push() and pop() methods in a typical implementation of a Queue/Linked List work but what I do want to know is what you actually define as a push or a pop? When can you name a method push()/pop()? What makes the insert()/add() method in a typical Tree implementation not a push()? My understanding is that push()ing means putting something to a position some special pointer is pointing to, and pop()ping an element means putting some object away some pointer is pointing to, but it doesn't seem to be clearly defined. Or does the naming matter at all?

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  • Sending while receiving in C

    - by Spidfire
    I've made a piece of code in what's on my server, the problem is that it doesn't send while im receiving. so if i send something to client 1 to client 2, client2 only receives if he sends something himself.. how can i solve this ? /* Thread*/ while (! stop_received) { nr_bytes_recv = recv(s, buffer, BUFFSIZE, 0); if(strncmp(buffer, "SEND", 4) == 0) { char *message = "Text asads \n"; rv = send(users[0].s, message, strlen(message), 0); rv = send(users[1].s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } }else{ char *message = "Unknown command \n"; rv = send(s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } } }

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  • C++ DWORD* to BYTE*

    - by NomeSkavinski
    My issue, i am trying to convert and array of dynamic memory of type DWORD to a BYTE. Fair enough i can for loop through this and convert the DWORD into a BYTE per entry. But is their a faster way to do this? to take a pointer to DWORD data and convert the whole piece of data into a pointer to BYTE data? such as using a memcpy operation? I feel this is not possible, im not requesting an answer just an experienced opinion on my approach, as i have tried testing both approaches but seem to fail getting to a solution on my second solution. Thanks for any input, again no answers just a point in the right direction. Nor is this a homework question, i felt that had to be mentioned.

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  • matlab: putting a circled number onto a graph

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

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  • c++ template function compiles in header but not implementation

    - by flies
    I'm trying to learn templates and I've run into this confounding error. I'm declaring some functions in a header file and I want to make a separate implementation file where the functions will be defined. Here's the code that calls the header (dum.cpp): #include <iostream> #include <vector> #include <string> #include "dumper2.h" int main() { std::vector<int> v; for (int i=0; i<10; i++) { v.push_back(i); } test(); std::string s = ", "; dumpVector(v,s); } now, here's a working header file (dumper2.h): #include <iostream> #include <string> #include <vector> void test(); template <class T> void dumpVector( std::vector<T> v,std::string sep); template <class T> void dumpVector(std::vector<T> v, std::string sep) { typename std::vector<T>::iterator vi; vi = v.begin(); std::cout << *vi; vi++; for (;vi<v.end();vi++) { std::cout << sep << *vi ; } std::cout << "\n"; return; } with implentation (dumper2.cpp): #include <iostream> #include "dumper2.h" void test() { std::cout << "!olleh dlrow\n"; } the weird thing is that if I move the code that defines dumpVector from the .h to the .cpp file, I get the following error: g++ -c dumper2.cpp -Wall -Wno-deprecated g++ dum.cpp -o dum dumper2.o -Wall -Wno-deprecated /tmp/ccKD2e3G.o: In function `main': dum.cpp:(.text+0xce): undefined reference to `void dumpVector<int>(std::vector<int, std::allocator<int> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' collect2: ld returned 1 exit status make: *** [dum] Error 1 So why does it work one way and not the other? Clearly the compiler can find test(), so why can't it find dumpVector?

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  • mysql++ compile error

    - by rizzo0917
    when i complie code that includes mysql headers i get the following errors: c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:27: error: 'int8_t' has a previous declaration as 'typedef signed char int8_t' c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:31: error: 'int32_t' has a previous declaration as 'typedef int int32_t' c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:32: error: 'uint32_t' has a previous declaration as 'typedef unsigned int uint32_t' Literally all I do is this. include cppconn/driver.h include cppconn/exception.h include cppconn/resultset.h include cppconn/statement.h include Now I can go into the file and comment the lines out that give me errors //typedef signed char int8_t; //typedef int int32_t; //typedef unsigned uint32_t; It compiles, but when I try to run the mysql code: sql::Driver *driver; driver = get_driver_instance(); I get this output test.exe exited with code -1073741515 Any Ideas?

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