Re: 64-bit weirdness with STL?

[Michael Tsang]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Robert Heller wrote:

> I have some code that is crashing with bad pointer problems.  The code,
> as far as I can tell, is not doing anything that is wrong.  The code
> compiles and runs just fine on a 32-bit system (same compiler, same
> version of libstdc++).  It compiles just fine on the 64-bit machine, but
> crashes somewhat randomly with pointer problems.  The problem seems to
> be specific to the basic_string template class.
> 
> I am using CentOS 5.4 on both machines:
> 
> gollum.deepsoft.com% uname -a
> Linux gollum.deepsoft.com 2.6.18-164.11.1.el5 #1 SMP Wed Jan 20 07:39:04
> EST 2010 i686 i686 i386 GNU/Linux
> sauron.deepsoft.com% uname -a
> Linux sauron.deepsoft.com 2.6.18-164.11.1.el5xen #1 SMP Wed Jan 20
> 08:06:04 EST 2010 x86_64 x86_64 x86_64 GNU/Linux
> 
> And the same *stock* CentOS C++ compiler and STL library:
> 
> gollum.deepsoft.com% rpm -q --qf '%{NAME}-%{VERSION}.%{RELEASE}.%{ARCH}\n'
> gcc-c++ libstdc++ libstdc++-devel gcc-c++-4.1.2.46.el5_4.2.i386
> libstdc++-4.1.2.46.el5_4.2.i386
> libstdc++-devel-4.1.2.46.el5_4.2.i386
> sauron.deepsoft.com% rpm -q --qf '%{NAME}-%{VERSION}.%{RELEASE}.%{ARCH}\n'
> gcc-c++ libstdc++ libstdc++-devel gcc-c++-4.1.2.46.el5_4.2.x86_64
> libstdc++-4.1.2.46.el5_4.2.x86_64
> libstdc++-4.1.2.46.el5_4.2.i386
> libstdc++-devel-4.1.2.46.el5_4.2.x86_64
> 
> Is there something I should *specificly* look for?
> 
> I changed
> 
> line += ","+trim(buffer);
> to
> line = line + "," + trim(buffer);
> 
> In one place (it seemed that the += operator for string was misbehaving).
> This only delayed the crash to later in the code.
> 
> line and buffer are basic_string objects.  Trim is:
> 
> /*
>  * Trim excess whitespace characters from both ends of a string.
>  */
>              
> const string System::whitespace = " \t\r\n";
>  
> string System::trim(string line) const {
>         string::size_type pos1, pos2;
>         for (pos1 = 0; pos1 < line.size() &&
>                        whitespace.find(line[pos1]) != string::npos;pos1++)
>                        ;
>         for (pos2 = line.size();
>              pos2 > pos1 &&
>              whitespace.find(line[pos2-1]) != string::npos;pos2--) ;
>         return line.substr(pos1,pos2-pos1);
> }
> 
> I have these additional functions which seem to be involved somehow:
> 
> /*
>  * Read the next line from a datafile, skipping any intervening comment
>  lines.
>  * Save the line of text and return true if successfull.  If EOF reached,
>  * generate and error and return false.
>  *
>  */
> 
> bool System::SkipCommentsGets(istream &stream,string& buffer,const char
> *message, char **outmessage) {
> #ifdef DEBUG
> cerr << "*** System::SkipCommentsGets()" << endl;
> #endif
> string trimString;
> while (getline(stream,buffer,'\n')) {
> #ifdef DEBUG
> cerr << "*** System::SkipCommentsGets: buffer = {" << buffer << "}" <<
> endl;
> #endif
> trimString = trim(buffer);
> #ifdef DEBUG
> cerr << "*** System::SkipCommentsGets: trimString = {" << trimString <<
> "}" << endl;
> #endif
> if (trimString.size() > 0 && trimString[0] != '\'') return true;
> }
> if (outmessage != NULL) {
> *outmessage = new char[strlen(message)+1];
> strcpy(*outmessage,message);
> }
> return false;
> }
> 
> /*
>  * Split a string on the specified delimeter and return a vector of
>  strings. */
> 
> vector<string> System::split(string s,char delimiter) const
> {
> vector<string> result;
> string::size_type start, end;
> #ifdef DEBUG
> cerr << "*** System::split(" << s << "," << delimiter << ")" << endl;
> #endif
> for (start = 0;start != string::npos;start = end+1) {
> end = s.find(delimiter,start);
> #ifdef DEBUG
> cerr << "*** System::split: start = " << start << ", end = " << end <<
> endl;
> #endif
> if (end == string::npos) {
> result.push_back(s.substr(start));
> return result;
> } else {
> result.push_back(s.substr(start,end-start));
> }
> }
> return result;
> }
> 
> In all cases I am careful to use the proper types (eg
> string::size_type) and whatnot as provided by the headers and I'm not
> casting between pointers and ints (of any size!).
> 
Can you provide a complete program that has the problem?
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)

iEYEARECAAYFAkuIoWAACgkQm4klUUKw07AryQCggzEZLAxsMncxja7qhxRi5rwY
4bcAn2FwnyoNkFeGJhPhuJYKhjjxYTEj
=CUMY
-----END PGP SIGNATURE-----