Same expression as the destination warning when using snprintf

See also questions close to this topic

• How do I manipulate the contents of a stat() struct?

  I have a stat struct, and I'm looking for a way to get data out of it to be manipulated. The program will successfully run and print the desired st_mtime value, but including either of the "seg-fault" lines below causes a segmentation fault in runtime.

          struct stat buf;
          time_t time_m;
          time_t sys_time = time(0);
          if(stat(sub_dirp->d_name,&buf)==0)
                   {
                       //time_m = buf.st_mtime;                                     //seg-fault
                       //double since_last = (difftime(sys_time, buf.st_mtime)/60); //seg-fault
                       printf("%d ", (int)buf.st_mtime);                          //This works.
                   }
  

  Both lines are attempting to manipulate the buf.st_mtime value in some way.

  I've had a hard time finding any examples of the usage of stat() that do anything other than print its contents, which makes me wonder if it's even possible.

  So my question is, if it is possible, what am I missing?

  P.S. I do wish to keep st_mtime in the Unix timestamp format to make it easier to manipulate.

  Edit: After realizing that st_mtime is itself its own struct (timespec), how can I access the st_mtime.tv_sec member?

  The compiler doesn't like buf.st_mtime.tv_sec one bit.

  compiler error
• What's purpose of __linecapp in getline, when it'll auto resize?

  It's all about second parameter of getline in stdio.h,

  I'll name it 'n' or '__linecapp' below.

  According to the document:

  If the buffer is not large enough to hold the line, getline() resizes it with realloc(3), updating *lineptr and *n as necessary.

  It'll automatically update line capacity, then why should we input __linecapp?

  P.S Someone ask before, but discussion didn't explain when we need it, or how to make it useful.
• Linked List Deletion function causing program to crash *wrong pointers?*

  In my program when a username is following another one and also has posted a "tweet" which is a string in an attempt to delete the followed username it breaks the program. I believe this is the code snippet in question. If anyone could help me identify the issue I would be thankful as I am learning the usage of linked lists for scale able projects. Thanks

  void deleteAccount(accountNodePtr *startPtr, accountNodePtr *curAcPtr, tweetsNodePtr *startTwtPtr){
  accountNodePtr acLoopPtr;
  accountNodePtr tempCur = *curAcPtr;
  followNodePtr followingPtr = tempCur->followingPtr;
  followNodePtr tempPtr;
  followNodePtr tempPtr2;
  tweetsNodePtr iterTwtPtr;
  iterTwtPtr = *startTwtPtr;
  *below here in question*
      tempCur = *curAcPtr;
  while (tempCur->followersPtr!=NULL){
      acLoopPtr = *startPtr;
      while (strcmp(acLoopPtr->username, tempCur->followersPtr->username)!=0){
          acLoopPtr=acLoopPtr->nextPtr;
      }
  
      if (strcmp(acLoopPtr->followingPtr->username, tempCur->username)==0){
          tempPtr=acLoopPtr->followingPtr->nextPtr;
          free(acLoopPtr->followingPtr);
          acLoopPtr->followingPtr=tempPtr;
      }else{
          tempPtr=acLoopPtr->followingPtr;
          while(strcmp(tempPtr->nextPtr->username, tempCur->username)!=0){
              tempPtr=tempPtr->nextPtr;
          }
          tempPtr2=tempPtr->nextPtr->nextPtr;
          free(tempPtr->nextPtr);
          tempPtr->nextPtr=tempPtr2;
      }
  
      tempPtr = tempCur->followersPtr->nextPtr;
      free(tempCur->followersPtr);
      tempCur->followersPtr=tempPtr;
  }
  

  This is the structure

  typedef struct followsNode {
  char username[MAX_USERNAME];
  struct followsNode *nextPtr;
  } followNode;
  
  typedef struct accountsNode {
      char username[MAX_USERNAME];
      struct followsNode *followersPtr;
      struct followsNode *followingPtr;
      struct accountsNode *nextPtr;
  } accountNode;
  
  typedef followNode *followNodePtr;
  typedef accountNode *accountNodePtr;
  
• Linux on Lightsail instance is asking for a password and it's not working

  I'm trying to restart mariaDB on Ubuntu but it's not letting me.

  I enter:

  systemctl restart mariadb
  

  and get:

  ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===
  
  Authentication is required to restart 'mariadb.service'.
  
  Authenticating as: Ubuntu (ubuntu)
  
  Password: 
  
  polkit-agent-helper-1: pam_authenticate failed: Authentication failure
  
  ==== AUTHENTICATION FAILED ===
  

  I have the same password for all functions so I do not understand why it is not working. What can I do?
• How to tag and store files, by metadata, in Python?

  I want to build a manual file tagging system like this. Given that a folder contains these files:

  data/
      budget.xls
      world_building_budget.txt
  a.txt
  b.exe
  hello_world.dat
  world_builder.spec
  

  I want to write a tagging system where executing

  py -3 tag_tool.py -filter=world -tag="World-Building Tool"

  will output

  These files were tagged with "World-Building Tool":
      data/world_building_budget.txt
      hello_world.dat
      world_builder.spec
  

  Another example. If I execute:

  py -3 tag_tool.py -filter="\.txt" -add_tag="Human Readable"

  It will output

  These files were tagged with "Human Readable":
      data/world_building_budget.txt
      a.txt
  

  I am not asking "Do my homework for me". I want to know what approach I can take to build something this? What data structure should I use? How should I tag contents in a directory?
• Installing pillow fails on Linux environment or Chrome OS. How do I fix this?

  When I try to install pillow with pip3, it gives me the following error message.

  failed building wheel for pillow

  [omitted text]

  Command "/usr/bin/python3 -u -c "import setuptools, tokenize;file='/tmp/pip-install-092vzzoo/pillow/setup.py';f=getattr(tokenize, 'open', open)(file);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, file, 'exec'))" install --record /tmp/pip-record-v4rw5g1c/install-record.txt --single-version-externally-managed --compile --user --prefix=" failed with error code 1 in /tmp/pip-install-092vzzoo/pillow/
• WebView2 JS injection returns empty json string

  With WebView2 for targeting Windows, I am trying to setup my own context menu. Either by selected text or by underlying element pointed by mouse click.

  However, I can't get DOM element by mouse operation or even by byId. I think my JavaScript injection or WebView property setting is something wrong, but not too sure. Can anyone suggest me the resolution?

  The version info.

  • OS : Windows 10 Pro 21H2 19044.1682
  • Visual Studio : Community 2022 17.1.6
  • WebView2 : 1.0.1185.39
  • Project Property: Target framework=.NET 6.0; Target OS version=10.0.19041.0

  Here's the testing code

  using Microsoft.Web.WebView2.Core;
  namespace WinFormsApp1
  {
      public partial class Form1 : Form
      {
          public Form1()
          {
              InitializeComponent();
              HTML(@"C:\temp\test.html");
          }
          public void HTML(string url)
          {
              webView21.CoreWebView2InitializationCompleted += WebView2Control_CoreWebView2InitializationCompleted;
              webView21.Source = new Uri(url);
          }
          private void WebView2Control_CoreWebView2InitializationCompleted(object? sender, CoreWebView2InitializationCompletedEventArgs e)
          {
              if (!e.IsSuccess)
              {
                  MessageBox.Show($"WebView2 creation failed, with exception : {e.InitializationException}");
                  return;
              }
              // subscribe to events we are interested in
              webView21.CoreWebView2.ContextMenuRequested += CoreWebView2_ContextMenuRequested;       // user clicked right mouse to show context menu
          }
          private async void CoreWebView2_ContextMenuRequested(object? sender, Microsoft.Web.WebView2.Core.CoreWebView2ContextMenuRequestedEventArgs e)
          {
              IList<CoreWebView2ContextMenuItem> menuItemList = e.MenuItems;
              menuItemList.Clear();  // clear default menu items, like prev, next, property
  
              //GETTING SELECTED TEXT
              string text = e.ContextMenuTarget.HasSelection ? e.ContextMenuTarget.SelectionText : ""; // it works
  
              if (string.IsNullOrEmpty(text))  // no text selection, then examine DOM
              {
              //GET AN UNDERLYING ELEMENT FROM MOUSE POINT
                  var result = await webView21.CoreWebView2.ExecuteScriptAsync($"document.elementFromPoint({e.Location.X},{e.Location.Y})");   //it doesn't work, just returns an empty JSON text (not null)
                  //var result = await webView21.CoreWebView2.ExecuteScriptAsync("function foo(){return 'foo() gets called';}; foo();");  //for testing purpose, it works
                  //var result = await webView21.CoreWebView2.ExecuteScriptAsync("function foo(){return document.getElementById('table-content'};foo();)");   //it returns an empty result
              }
              // TO DO
              // setup menuItem tree based on the result we got
              //......
              //......
              e.Handled = true;
          }
      }
  }
  
• site only opens in CefSharp

  zaakr.net is a site can be opened only in zaakr.exe application or through android(.apk), when opened in browser u been redirected to https://browser.zaakr.net so u download there application, (.exe) file is using cefsharp as a browser so it can access website, from 2 month i could open it from chromium as cefsharp uses chromium, now i can't access website through chromium for some reason idk, i even made a cefsharp browser myself using visual studio nothing worked all the time i been redirected to browser.zaakr.com, i want to access through any browser that have devtools available for a project, note that application zaakr.exe is still using cefsharp even the older version still can access site. i would appreciate any help, sry for any spelling mistakes, thanks.
• Subprocess $Env:Path python: The filename, directory name, or volume label syntax is incorrect

  I am trying to change the windows environment variables, but I am having trouble doing so.

  Before I tried to use os.environ() I tried out using powershell commands and adding a string to $Env:Path which worked, but removing it with:

  $env:Path = ($env:Path.Split(';') | Where-Object -FilterScript {$_ -ne $Remove}) -join ';'
  

  however didn't seem to remove it being my path I want to add ("FFmpeg:C:\Users\user\AppData\") and adding it with += C:/Users/etc.. didn't see, the way to go.

  Another way I tried to add vars through the Powershell commands was using SetEnviormentVariable and it seemed to work fine but once I restarted my PC the entry I made with it was gone.

  Sadly though all in the end all my powershell commands didn't work with subprocess. Whatever command it was I was using here I got:

  PS C:\Users\Me123> python
  >>> import subprocess
  >>> subprocess.run("$Env:Path", shell=True)
  The filename, directory name, or volume label syntax is incorrect.
  
  CompletedProcess(args='$Env:Path', returncode=1)
  
• Compile all C files in all of the children directories

  So, I'm making a game with raylib and I need to compile all the .c files at once.

  The files are in separate folder inside the 1st one(Like "MainFolder/PlayerFiles").

  I know how that gcc -o game *.c -L/usr/local/lib -lraylib compiles all the files inside the directory and creates a exec.

  How can I compile all the .c files in all of the children folders.

  Thanks in advance!!!
• how to get the bare bone compiled binary code of a C function?

  I'm trying to implement an embedded firmware on an stm32 F4 micro that takes an binary code from the serial and execute it on the micro.

  The idea is pretty simple of course the only tricky part is that since on the serial is complicate to send raw binary data I'm going to send everything through base64 encoding.

  Here's the code:

  #include <Arduino.h>
  #include <base64.hpp>
  
  size_t read_serial_line(char *msg, size_t len, size_t timeout = 0) {
    const auto start = millis(); 
    size_t sz = 0;               
  
    do {
      while (not Serial.available()) {
        if (timeout > 0 and millis() > start + timeout) {
          return -1;
        }
      }
  
      msg[sz] = Serial.read();
  
      if (msg[sz] == '\r') {
        msg[sz] = '\0'; // replacing the end line with the end string
  
        // the next char must be a \n char since the Serial.println of arduino
        // works like that
        while (Serial.read() != '\n')
          ; // I discard it
  
        // now sz contains the length of the string as returned by strlen
        break; // end of line
      }
  
      if (timeout > 0 and millis() > start + timeout) {
        return -1;
      }
    } while (++sz < len);
  
    return sz; 
  }
  
  void setup() {
    Serial.begin(9600);
  
    Serial.println("begin!");
  }
  
  void loop() {
    char *msg = new char[2048](); // big line
  
    auto sz = read_serial_line(msg, 2048);
  
    Serial.print("\tlooping...");
    Serial.println(sz);
    Serial.print("received: ");
    Serial.println(msg);
  
    uint8_t *code = new uint8_t[2048]();
  
    sz = decode_base64(msg, code);
  
    Serial.println(sz);
  
    delay(1000);
  
    int (*code_fn)() = (int (*)())code;
  
    int c = code_fn();
  
    Serial.println(c);
  
    delete code;
    delete msg;
    delay(1000);
  }
  

  The next problem is to be able to compile and get the compiled binary code from this simple C function:

  int fn() {
     return 3;
  }
  

  Here you can see the assembly of this stupid function.

  I tried, of course using the same tool chain used for the main code of the micro, to compile it with gcc using the option for the position independent code and then I tried to copy the .text secion with objcopy, to finish I took the text returned from the xxd command, I encoded it in base64 and I sent it to the micro.

  here are the commands that I used:

  $ arm-none-eabi-gcc -fPIC -c test.c
  $ arm-none-eabi-objcopy -j .text test.o test.bin 
  $ xxd -p test.bin 
  

  As I expected this idea is not working, my hypothesis is that I'm getting more then just the binary codes of the function from this process. I have this idea because the output file test.bin is pretty big 440 bytes that seems to me a little bit too much for literally 7 assembly instructions.

  So that's the reason of my question: How do I get the binary code and only that code?
• terminate called after throwing an instance 'std::__ios_failure'

  In Ubuntu20.04 gcc9.4.0

  `void read_txt_config(const std::string &path) { std::cout << std::endl << "Reading configuration file: ";

      std::ostringstream batch_out;
      batch_out
          << path
          << "config.txt";
  
      std::string str_temp = batch_out.str().data();
      std::ifstream fin;
      fin.exceptions(std::ios::failbit | std::ios::badbit);
      fin.open(str_temp.c_str());
  
      if (!fin.good())
      {
          std::cout << " reading failed, there is no config.txt, the program will use the default param_nameeters. " << std::endl;
      }
      else
      {
          ...
          ...
       }       
   fin.close();}
  

  when the code run to fin.close();

  I got

  terminate called after throwing an instance 'std::__ios_failure' what(): basic_ios::clear: iostream error Aborted(core dumped)
• Ocaml compile on eclipse using Makefile occurs no file error even if there is

  

  When I try to compile my project with Makefile, it keeps show error that there is no file lang.ml even if there is in same path. It seems that make.exe can't totally recognize the file contents in projects. Maybe there is problem with entering directory /home/mario/eclipse/assignment/miniML_skel folder, but I can't find the way how to check or manange the path where make.exe actually gone through. However, the absolute path of project is C:/OCaml64/home/mario/eclipse/assignment/miniML_skel and workspace is set as C:/OCaml64/home/mario/eclipse/assignment. I create this project as an Ocaml Empty Makefile Project and import contents file from some other folder.

  

  

  Here is paths of preference and project.

  Note that if I compile lang.ml separately and create lang.cmo file, then make process normally detect it and continue.
• Eclipse C++, Compiling via cmd works, compilling in eclipse does not

  I have a TCP Client program (TCPClient.cpp) using winsock library. An *.exe is generated successfully if I use command line with the following call:

  g++ TCPClient.cpp -o TCPClient.exe -lws2_32
  

  When I try to compile and link the same script within Eclipse/C++ using MinGW I seem to get the *.o file generated but I get an error when generating the *.exe. Thus, the error is generated if Ecplise/C++ does the following (linker call):

  g++ -o TCPClient.exe TCPClient.o -lws2_32 
  

  I get multiple errors:

  enter C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84.
  ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x2a0): multiple definition of
  _mingw32_init_mainargs
  c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../crt2.o:(.text+0x2a0): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84. ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x2e0): multiple definition of
  mainCRTStartup' c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../crt2.o:(.text+0x2e0): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84. ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x300): multiple definition of WinMainCRTStartup' c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../crt2.o:(.text+0x300): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84. ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x320): multiple definition of atexit' c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../crt2.o:(.text+0x320): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84. ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x330): multiple definition of _onexit' c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../crt2.o:(.text+0x330): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84. ./src/TCPClient.o:cygming-crtbegin.c:(.text+0x340): multiple definition of
  `__gcc_register_frame' c:/mingw/bin/../lib/gcc/mingw32/6.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0x0): first defined here C:\MinGW\bin\ld.exe: Dwarf Error: Could not find abbrev number 84.here

  The following is interesting: I get the same errors if I use the cmd-line and first generate a .o file and then try to generate a *.exe. Both of the following calls in cmd-line result in the error from above:

  g++ TCPClient.o -o TCPClient.exe -lws2_32
  
  g++ TCPClient.o -o TCPClient.exe 
  

  This means: If in cmd-line I only specify that I want to generate (a *.exe from my *.cpp) everything works fine. But - as a user - doing those two steps separately does not work.

  Cmd-Line g++ call seems to "know" what to do here. As a user I never see the *.o file when directly generating a *.exe. But I think it must be generated anyway? Am I wrong? Why does cmd-line without further specification know how to deal with the .o file? ... Is it possible to find out from any source what a call to "g++" does when called via command line? Of course I want the same settings integrated in eclipse/c++.