libstdc++/5492: basic_string seems to fail to use template-defined allocator.

[bkoz@gcc.gnu.org]

Synopsis: basic_string seems to fail to use template-defined allocator.

State-Changed-From-To: analyzed->feedback
State-Changed-By: bkoz
State-Changed-When: Sat Apr 20 16:55:25 2002
State-Changed-Why:
    I don't think this is a bug.
    
    Here's a testcase:
    
    #include "post_stl.h"
    #include <iostream>
    #include <sstream>
    #include <vector>
    #include <exception>
    #include <stdio.h>
    
    using namespace std;
    
    storage* sto;
    
    struct A
    {
      pstring 	msg;
      double 	num;
      short		pad[5];
    
      A(const char* s, streamsize len, double d) : msg(s, len), num(d) { }
    
      virtual 
      ~A() { }
    
      virtual string 
      getInfo()
      {
        ostringstream out;
        out << "class type 'A'" << endl;
        out << "msg object address = " << (void*)(&msg) << endl;
        out << "msg data address = " << (void*)(msg.data()) << endl;
        out << "msg = '" << msg.c_str() << "'" << endl; 
        out << "num = '" << num << "'" << endl;
        return out.str();
      }
    };
    
    typedef vector<A*, post_alloc<A*> > A_vector;
    
    int main()
    {
      sto = new storage("stringtest.odb");
      if (sto->open(storage::fixed)) 
        {
          A_vector *root = (A_vector*)sto->get_root_object();
          if (root != NULL) 
    	{
    	  cout << "Existing database found at " << root << endl;
    	  for (A_vector::iterator i = root->begin(); i != root->end(); i++) 
    	    {
    	      cout << "object found at " << *i << ":" << endl;
    	      cout << (*i)->getInfo();
    	    }
    
    	} 
          else 
    	{
    	  root = new (*sto) A_vector;
    	  cout << "Creating database at " << root << endl;
    	  sto->set_root_object((object*)root);
    	}
    
          cout << endl;
          cout << "Add some lines.  Terminate input with empty line." << endl;
    
          while (cin.good()) 
    	{
    	  char buf[256];
    	  cin.getline(buf, 256);
    	  streamsize len = cin.gcount() - 1;
    	  if (!len) 
    	    {
    	      cout << "done." << endl;
    	      sto->flush();
    	      sto->close();
    	      return EXIT_SUCCESS;
    	    } 
    	  else 
    	    {
    	      A* a = new (*sto) A(buf, len, 44.5);
    	      cout << "created new A object at " << a << endl;
    	      cout << a->getInfo() << endl;
    	      root->push_back(a);
    	    }
    	}
        } 
      else 
        {
          cerr << "Failed to open storage" << endl;
          return EXIT_FAILURE;
        }
    }
    
    Gives:
    %a.out 
    Creating database at 0x400005ac
    
    Add some lines.  Terminate input with empty line.
    this is a test
    
    created new A object at 0x4000060c
    class type 'A'
    msg object address = 0x40000610
    msg data address = 0x81344dc
    msg = 'this is a test'
    num = '44.5'
    
    And then re-running the binary:
    
    %a.out 
    Existing database found at 0x400005ac
    object found at 0x4000060c:
    class type 'A'
    msg object address = 0x40000610
    msg data address = 0x81344dc
    msg = ''
    num = '44.5'
    
    
    It looks like 
    
    1) find_storage in storage.h, line 248
    has problems finding a block for std::string because sizeof(string) != sizeof(string) + sizeof(string::_Rep)
    
    2) allocate, post_stl.h line 92:
    
    ends up using malloc to get storage.
    
    The results are obvious from the above output.
    
    I think this is an error with the POST++ allocation strategy, or else I'm not configuring it to work correctly.
    
    Thoughts?
    
    -benjamin

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=5492