PRB: _mktemp() May Return the Same Name Between Threads

MORE INFORMATION

Sample Code

/* Compile options needed:    /MT /D_CONSOLE
*/ 
#include <windows.h>

#include <process.h>    /* _beginthread, _endthread */ 
#include <io.h>         /* _mktemp */ 
#include <stdio.h>

void Check1(void *);
void Check2(void *);
char *path1, *path2, *path3;
char templateName[4][9] = {"fnXXXXXX","fnXXXXXX","fnXXXXXX",
                 "tnXXXXXX"};
void main()
{
  _beginthread(Check1, 0, NULL );
  _beginthread(Check2,0,NULL);
  Sleep(200L);
  printf("Program finished\n");
}

/* Check */ 
void Check1( void * dummy  )
{
  FILE *fp;

  path1 = _mktemp(templateName[0]);

  Sleep(100L);  // Give thread 2 a chance to call mktemp before the
                  // the file is actually opened
  if (path1 != NULL)
     if ((fp = fopen(path1,"w")) == NULL) {
     printf("Thread 1 - Failed to open file %s\n",path2);
       _endthread();
     }
  fclose(fp);
  remove(path1);
  printf("Thread 1 - File %s successfully opened\n",path1);
  _endthread();
}

/* Check 2 */ 
void Check2( void * dummy  )
{
  FILE *fp;

  // Path2 is set to the same as path1 which is INCORRECT
  path2 = _mktemp(templateName[2]);

  // Workaround is to specify an unused template name

  if (path2 != NULL)
     if ((fp = fopen(path2,"w")) == NULL) {
     printf("Thread 2 - Failed to open file %s\n",path2);
       _endthread();
     }
  fclose(fp);
  remove(path2);
  printf("Thread 2 - File %s successfully opened\n",path2);
  _endthread();
}