title: Using libarchive in Qt - build errors
body: <p>I've got hold of <a href="http://code.google.com/p/libarchive/" rel="nofollow">libarchive</a> and built the examples on both Windows and Linux following the <a href="http://code.google.com/p/libarchive/wiki/BuildInstructions" rel="nofollow">build instructions</a>.</p>
  
  <p>I now want to use this library in my project, which is Qt based, so I'm using Qt creator. I've added the include paths for libarchive in my pro file, but when I compile I get errors saying "undefined reference to '<em>imp</em>_archive_read_new'" and so on.</p>
  
  <p>This is my code at the moment:</p>
  
  <pre><code>    #include &lt;stdio.h&gt;
      #include &lt;stdlib.h&gt;
      #include &lt;string.h&gt;
      #include &lt;stdint.h&gt;
      #include "archive.h"
      #include "archive_entry.h"
  
      cTarFileManager::cTarFileManager()
      {
        struct archive *a;
        struct archive_entry *entry;
        int r;
        int64_t entry_size;
        a = archive_read_new();
        archive_read_support_compression_none(a);
        archive_read_support_format_tar(a);
        r = archive_read_open_filename(a, "0000.tar", 1024);
        if (r != ARCHIVE_OK)
        {
          printf("archive not found");
        }
        else
        {
          while (archive_read_next_header(a, &amp;entry) == ARCHIVE_OK)
          {
            const char *currentFile = archive_entry_pathname(entry);
            char *fileContents;
            entry_size = archive_entry_size(entry); //get the size of the file
            fileContents = (char*)malloc(entry_size); //alloc enough for string - from my testing I see that this is how many bytes tar and ls report from command line
            archive_read_data(a, fileContents, entry_size); //read data into fileContents string for the HTML file size
            if(strcmp(currentFile, "vendar-definition.html") == 0)
            {
              printf("file name = %s, size = %ld\n", currentFile, entry_size);
              printf("%s\n\n", fileContents); //this output over-reads chars from another file in this tar file
            }
            free(fileContents); //free the C string because I malloc'd
          }
        }
        printf("exit");
      }
  </code></pre>
  
  <p>Here is the full list or errors I get:
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:16: undefined reference to <code>_imp__archive_read_new'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:17: undefined reference to</code><em>imp</em>_archive_read_support_compression_none'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:18: undefined reference to <code>_imp__archive_read_support_format_tar'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:19: undefined reference to</code><em>imp</em>_archive_read_open_filename'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:28: undefined reference to <code>_imp__archive_entry_pathname'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:30: undefined reference to</code><em>imp</em>_archive_entry_size'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:32: undefined reference to <code>_imp__archive_read_data'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:26: undefined reference to</code><em>imp</em>_archive_read_next_header'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:16: undefined reference to <code>_imp__archive_read_new'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:17: undefined reference to</code><em>imp</em>_archive_read_support_compression_none'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:18: undefined reference to <code>_imp__archive_read_support_format_tar'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:19: undefined reference to</code><em>imp</em>_archive_read_open_filename'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:28: undefined reference to <code>_imp__archive_entry_pathname'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:30: undefined reference to</code><em>imp</em>_archive_entry_size'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:32: undefined reference to <code>_imp__archive_read_data'
  D:\Tar-build-desktop-Qt_4_7_4_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../Tar/TarFileManager.cpp:26: undefined reference to</code><em>imp</em>_archive_read_next_header'</p>