Question

The following is in C++.
I have a string that contains the environment variables I need to split it at the declaration of each variable & store it in a string:

char* envVars = "=::=::\0system=blah\0othervar=blah\0"

So I am using cstring functions to split the string at the occurence of the null terminator char ‘\0’ but it’s just going into an infinite loop. Why?

SOLUTION Found: look at code comments:

vector <string> GetEvironmentVariables()
{
   vector <string> envVariables;
   char* environVar = GetEnvironmentStrings();
   char* pos        = strchr( environVar, '\0' );

   // As far as I know environVar =::=::\0environVar1=...\0environVar2=...\0" 
   // so the string has many NULL terminators  

   while ( pos != NULL )
   {
       char* buffer;
       strncpy( buffer, environVar, strlen(pos) );   // on the 1st iteration: buffer SHOULD = "=::=::\0", 2nd buffer SHOULD = "environVar=...\0"
       envVariables.push_back( string(buffer) );
       environVar = pos;                            // SOLUTUION: I need to move over the '\0' pos points to so: environVar = ++pos;
       pos        = strchr( environVar, '\0' );

       printf("Var: %s \n", envVariables.back().c_str() ); 
       printf("env: %s \n", environVar);
       system("PAUSE");
       // prints out this:
       // Var: cRek (same junk each iteration)
       // env: 
       // Press any key to continue....
   }

   FreeEnvironmentStrings( environVar ); 
   return envVariables;       
}

Answer 1

I would have expected this to exit immediately, but actually the man page says:

The terminating null character is considered to be part of the string; therefore if c is '\0', the functions locate the terminating '\0'.

Of course, the result of pos = strchr(environVar, '\0'); is that *pos == '\0' and strlen(pos) == 0. So you always copy exactly zero characters. Not useful.

You also set environVar = pos;, without skipping over the NUL character. So the next call to strchr returns environVar and no more progress is ever made.

---

You’ve also forgotten to initialize buffer, you’re passing a wild pointer to strncpy which will corrupt a random part of memory. This bug will probably rear its ugly head as soon as you fix the fact that the length parameter is always zero.