Saving and printing from struct in C

See also questions close to this topic

• Do functions which are not defined as async-safe, such as mmap(2), effect other async-safe functions called in signal handler?

  I am making a library which gets injected into processes and redefines some of functions, such as open(2) to do some tasks before calling real open(2). My library would call mmap(2). As open(2) is async safe, is it possible that someone using the library who called open(2) in signal handler and where my library also added a call to mmap(2) could make his call to open(2) go wrong?
• Why 2 is not smaller than 10 on Codeblocks?

  I just worked to my final exam with simple codes; when I try to sorting strings, I face annoying error. Why 2 is not smaller than 10 on my CodeBlocks IDE but is smaller than 10 on real and onlinegdb.com?

  This is the annoying code:

  #include <string.h>
  #include <stdio.h>
  #define STR_SIZ 20
  
  int main()
  {
      char strArr[][STR_SIZ] = {"abc", "hdas", "sdfasf", "kakldf", "caksl", "casd", "keam", "cznjcx", "mnxzv", "jkalkds"};
      char minStr[STR_SIZ];
      strcpy(minStr, strArr[0]);
      int N = sizeof(strArr)/sizeof(minStr);
     // int N = 10;
      for(int x = 0; x < N-1; x++)
      {
          printf("%d", x);
          strcpy(minStr,strArr[x]);
          int j;
          for(j=1+x; j < 10; j++)
          {
              printf("%4d\n", j);
              int cmp = strcmp(strArr[j], minStr);
              if(cmp < 0)
                  strcpy(minStr,strArr[j]);
          }
          char temp[STR_SIZ];
          strcpy(temp,strArr[x]);
          strcpy(strArr[x], minStr);
          strcpy(strArr[j], temp);
      }
  
  
      return 0;
  }
  

  Output on onlinegdb.com:

  0   1
     2
     3
     4
     5
     6
     7
     8
     9
  1   2
     3
     4
     5
     6
     7
     8
     9
  2   3
     4
     5
     6
     7
     8
     9
  3   4
     5
     6
     7
     8
     9
  4   5
     6
     7
     8
     9
  5   6
     7
     8
     9
  6   7
     8
     9
  7   8
     9
  8   9
  

  Output on CodeBlocks:

  0   1
     2
     3
     4
     5
     6
     7
     8
     9
  1   2
     3
     4
     5
     6
     7
     8
     9
  2
  

  PS: I just have used Codeblock in the morning and it was okey with executing.
• Parse func f(arg1, arg2: type) in lex yacc compiler

  I successfully parse:

  func f(a: int) return int{}
  

  And

  func f(a: int; b: string) return int{}
  

  But I fail to parse

  func f(a, c: int; b: string) return int{}
  

  My compiler fails to catch whatever comes behind the comma and I cant figure out how to fix it. What I get in the third case is c as an int, b as a string and null as an a (as opposed to a as an int).

  The rules I use-

  function:
  FUNC iden_name O_PAREN parameters C_PAREN RETURN ident_type block { 
      Node * left = makeTripNode("FUNCTION", $7, $2, $4 );
      Node * right = $8;
      $$ = makePairNode("FUNCTION", left, right ); 
  }
  parameters:
  parameters SEMICOLON parameter { $$ = makePairNode("PARAMETERS", $1, $3); }
      | parameters COMMA parameter { $$ = makePairNode("PARAMETERS", $1, $3); }
      | parameter {$$ = $1;}
      ;
  parameter:
  iden_name COLON ident_type { $$ = makePairNode("PARAM", $3, $1); }
      | iden_name {$$ = $1;}
      ;
  
• How to copy files using kohsuke github

  I am working with org.kohsuke.github.*;

  1. I have a sample repository where I have a commit (sha) with a bunch of files which serve as a template.
  2. When I get a request on my app with a repo name xyz, I need to fork repo xyz, grab files from #1 add the files to the forked repo and submit a PR from forked repo to original repo xyz.

  Is this possible via kohsuke github?

  Gone through documentation of kohsuke

    public static GHRepository createFork(String repo) throws IOException{
          GHRepository mainRepo = github.getRepository(repo);
          GHRepository forkedRepo = mainRepo.fork();
          GHCommit commit = copyFiles();
          /*QUESTION: Here is where I need help. Now that I have the 
           commit that has the files I need how to I add them to 
          forkedRepo?******** */
          GHCommitBuilder builder = forkedRepo.createCommit();
          return forkedRepo;
      }
  
      public static GHCommit copyFiles() throws IOException {
          GHRepository mainRepo = github.getRepository("sandbox/xyz");
          /* xxxxxxxxx is the sha of commit that has templated files.        
          GHCommit commit = mainRepo.getCommit("xxxxxxxxxxx"); 
  
          GHContent content = new GHContent();
          return commit;
      }
  
• How can I change downloading file name?(now it use default value)

  I need to show file preview and when i click download, it use default file name. Can i set file name in this case:

    const win = window.open();
    win.document.write('<html><head></head><body style="margin: 0;">' +
      '<iframe src="' + result.ReturnValue.DataBase64String + '" frameborder="0" style="border:0; top:0px; left:0px;' +
      'bottom:0px; right:0px; width:100%; height:100vh;" allowfullscreen></iframe></body></html>');
    win.document.title = result.ReturnValue.FileName;
  
• how to permission for audio file play on browser and not download

  i have a c-panel host, i upload mp3 files, when i see on browser it's begin to download and not play How to fix when open in browser begin to play same the below sample and not download directly; my audio link: http://play.mmasomi.ir/mp3/Evan%20Band%20-%20To%20Ke%20Maroufi.mp3

  i wants to be same this files: https://wavesurfer-js.org/example/media/demo.wav

  please help me
• Using data on an initializer_list

  So I'm looking at the data function and I see that it has this overload:

  template <class E>
  constexpr const E* data(std::initializer_list<E> il) noexcept;
  

  Let's say that I call foo(data({ 0, 13, 42 })) with:

  void foo(const int* param) {
      cout << param[0] << ' ' << param[1] << ' ' << param[2] << endl;
  }
  

  Am I in fact making a copy of the initializer_list?
• C++ error when attempting to pass and return a set of pointers from a function

  I have two (really three, but one is irrelevant here) header files with classes in them for a project. One Node class that includes a set of pointers to other nodes (its like a tree), and the other class is a graph class (entitled AML) that holds a set of all the pointers to nodes in their respective layers.

  I wanted to write my own C++ set operations (because I'll need them), so I decided to declare a namespace that has the set operation functions. However when I try to use these set operations in my Node class, I get an error. Here is the relevant code:

  aml.h

  #pragma once
  #include <set>
  #include "Node.h"
  #include "constant.h"
  
  using namespace std;
  class aml
  {
  // class stuff
  };
  
  namespace setops {
      set<Node*> set_union(set<Node*>  &a, set<Node*>  &b);
      // other set operations
  }
  

  aml.cpp

  #include "aml.h"
  
  using namespace std;
  
  
  //class functions
  
  set<Node*> setops::set_union(set<Node*>  &a, set<Node*>  &b) {
      set<Node*> c;
      for (Node* data : a) {
          c.insert(data);
      }
      for (Node* data : b) {
          c.insert(data);
      }
  
      return c;
  }
  

  Node.h

  #pragma once
  #include <string>
  #include <set>
  #include "aml.h"
  #include "constant.h"
  
  using namespace std;
  class Node
  {
  private:
      set<Node*> lower;
  public:
      set<Node*> getLower();
      set<Node*> GL();
  };
  

  and here is the GL() method in which the error occurs. This is supposed to return the set of all nodes that can be reached by traveling down the tree. getLower() returns the lower set that houses all a node's children.

  Node.cpp

  #include "Node.h"
  
  set<Node*> Node::getLower() {
      return this->lower;
  }
  
  set<Node*> Node::GL() {
      set<Node*> lowerSet;
      lowerSet.insert(this);
      if (this->lower.size() == 0) {
          return lowerSet;
      }
      set<Node*> recurse;
      for (Node* node : this->lower) {
          recurse = node->GL();
          lowerSet = setops::set_union(lowerSet, recurse); //This is the error line
      }
      return lowerSet;
  }
  

  I marked the problem line. It actually has three errors, one on each parameter and one of the equals sign. The errors say (all of them are pretty much the same, but this is the parameter one)

  a reference of type "set::set<<error-type>*, std::less<<error-type>*>, std::allocator<<error-type>*>& "(non-const qualified) cannot be initialized with a value of type "set::set<Node*, std::less<Node*>, std::allocator<Node*>> "

  I have no idea what is going on, any help appreciated!
• Having issue with vector vector pointer allocation inside a class

  Having a simple issue with vector vector pointer allocation:

  I was trying to allocate and put a value inside a class where vector-vector-pointers are initialized in the main function. It is passed by reference in the test_class. Now, the allocation of this vector-vector-pointers is allocated in the test_class method test_function(). In main, I should get the value of the pointers but I find that the pointers aren't allocated.

  1. Tested without having any class, e.g. test_function(vector<vector<int*>>), it works.
  2. Tested with having a class, it didn't work.

  #include <iostream>
  #include <vector>
  
  using namespace std;
  
  #define N 20
  
  class test_class {
  private:
      vector<vector<int*>> a_class;
  
  public:
      test_class(vector<vector<int*>>& a) : a_class(a) {}
      void test_function() {
          for(int i = 0; i < N; i++)
              for(int j = 0; j < N; j++) a_class[i][j] = new int[2];
  
          for(int i = 0; i < N; i++)
              for(int j = 0; j < N; j++) {
                  *(a_class[i][j] + 1) = i + j + 1;
                  *a_class[i][j] = i + j;
              }
      }
  };
  int main() {
      vector<vector<int*>> a_main;
  
      a_main.resize(N);
      for(int i = 0; i < N; i++) a_main[i].resize(N);
      for(int i = 0; i < N; i++)
          for(int j = 0; j < N; j++) a_main[i][j] = nullptr;
  
      test_class* obj = new test_class(a_main);
      obj->test_function();
  
      for(int i = 0; i < N; i++) {
          cout << N << " \n";
          for(int j = 0; j < N; j++)
              cout << *(a_main[i][j]) << "    " << *(a_main[i][j] + 1) << "\n";
      }
      return 0;
  }
  

  "test_func.cc" 50L, 826C                  
  
  (gdb) run
  Starting program:test_func.o
  20
  
  Program received signal SIGSEGV, Segmentation fault.
  0x0000000000400cad in main () at test_func.cc:46
  46                      cout<<*(a_main[i][j])<<"    "<<*(a_main[i][j]+1)<< "\n";
  
• How to create a custom NaN (single precision) in python without setting the 23rd bit?

  I'm trying to create floating-point NaNs by choosing the fraction bits. But it seems that python float always set the 23rd fraction bit (IEEE754 single) when it interprets a NaN.

  So, my question is: is it possible to define a float nan in python without it setting the 23rd bit?

  (I'm using Python 2.7)

  NaNs in IEEE 754 have this format:
  sign = either 0 or 1.
  biased exponent = all 1 bits.
  fraction = anything except all 0 bits (since all 0 bits represents infinity).

  So, a hex representation for a NaN could be 0x7F800001, but when interpreting this int as a float and interpreting it back to int gives 0x7FC00001

  1st try: struct.pack/unpack:

  import struct
  
  def hex_to_float(value):
      return struct.unpack( '@f', struct.pack( '@L', value) )[0]
  
  def float_to_hex(value):
      return struct.unpack( '@L', struct.pack( '@f', value) )[0]
  
  print hex(float_to_hex(hex_to_float(0x7f800001)))
  # 0x7fc00001
  

  2nd try: ctypes

  import ctypes
  
  def float2hex(float_input):
      INTP = ctypes.POINTER(ctypes.c_uint)
      float_value = ctypes.c_float(float_input)
      my_pointer = ctypes.cast(ctypes.addressof(float_value), INTP)
      return my_pointer.contents.value
  
  def hex2float(hex_input):
      FLOATP = ctypes.POINTER(ctypes.c_float)
      int_value = ctypes.c_uint(hex_input)
      my_pointer = ctypes.cast(ctypes.addressof(int_value), FLOATP)
      return my_pointer.contents.value
  
  print hex(float2hex(hex2float(0x7f800001)))
  # 0x7fc00001L
  

  3rd try: xdrlib packers. Same result.
• Segmentation fault on return statement of struct: How can I fix this?

  I'm creating an AST for a parser i'm working on however when calling getRoot() i get a segmentation fault and can't seem to figure out why. I'm half sure it's something blatantly obvious but after staring so long at the code I'm getting nothing.

  Tried to research the problem and what i found is that i could possibly be messing up the stack but can't see how.

  The segmentation fault occurs when i run the following code:

  AST ast;
  ast.getRoot();
  

  The .cpp file:

  #include "AST.h"
  
  Compiler::AST::AST() {
  
  }
  
  void Compiler::AST::addNode(Node node) {
     if(rootNull){
        setRoot(node);
        rootNull = false;
     }else{
        root.childNodes.push_back(node);
     }
  }
  
  Compiler::AST::Node Compiler::AST::getRoot() {
     return root;
  }
  
  void Compiler::AST::setRoot(Compiler::AST::Node node) {
     this->root = node;
  }
  

  the .h file:

  #ifndef COMPILERS_ASSIGNMENT_AST_H
  #define COMPILERS_ASSIGNMENT_AST_H
  
  #include <string>
  #include <vector>
  #include <iostream>
  
  namespace Compiler {
  
  
      class AST {
      public:
          struct Node{
              std::string descriptor;
              std::vector <Node> childNodes;
          };
          typedef Node Node;
          AST();
          void addNode(Node);
          Node getRoot();
      private:
          Node root;
          bool rootNull = true;
          void setRoot(Node);
      };
  }
  
  #endif //COMPILERS_ASSIGNMENT_AST_H
  
• Struct inside struct: 'Illegal reference to non-static member' error

  I need to create a struct inside struct. How to code the constructor correctly? Do I need to create two constructors separately for A and B or can I use only one 'outside' constructor for A like in example below? My attempts resulted in C2597 error.

  struct A
  {
      struct B
      {
          unsigned n;
          int* d;
      };
  
      A(unsigned c)
      {
          B::n = c; // C2597
          B::d = new int[c]; // C2597
      }
  };