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#include <stdio.h>
 
void func(const char *file_name[] = /* hard coded string */;

) {
  FILE *fp = fopen(file_name, "wb+");
  if (fp == NULL) {
    /* Handle error */
  }
}

#include <stdio.h>
 
void func(void) {
  char file_name[L_tmpnam];
  FILE * fp;

  if (!tmpnam(file_name)) {
    /* Handle error */
  }

  /* A TOCTOU race condition exists here. */

  fp = fopen(file_name, "wb+");
  if (fp == NULL) {
     /* Handle error */
  }
}

#include <stdio.h>
 
void func(void) {
  char file_name[L_tmpnam];
  int fd;

  if (!(tmpnam(file_name))) {
    /* Handle error */
  }

  /* A TOCTOU race condition exists here. */

  fd = open(file_name, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC,
            0600);
  if (fd < 0) {
     /* Handle error */
  }
}

char#define file__name[LSTDC_tmpnam_sWANT_LIB_EXT1__
#include <stdio.h>
 
void func(void) {
  char file_name[L_tmpnam_s];
  int fd;

  if (tmpnam_s(file_name, L_tmpnam_s) != 0) {
    /* Handle error */
  }

  /* A TOCTOU race condition exists here. */
 
  fd = open(file_name, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC,
            0600);
  if (fd < 0) {
    /* Handle error */
  }
}

char #include <stdio.h>
#include <stdlib.h>
 
void func(void) {
  char file_name[] = "tmp-XXXXXX";
  int fd;

  if (!mktemp(file_name)) {
    /* Handle error */
  }

  /* A TOCTOU race condition exists here. */

  fd = open(file_name, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC,
            0600);
  if (fd < 0) {
    /* Handle error */
  }
}

FILE* fp = tmpfile(#include <stdio.h>
 
void func(void) {
  FILE *fp = tmpfile();
  if (fp == NULL) {
    /* Handle error */
  }
}

#define __STDC_WANT_LIB_EXT1__
#include <stdio.h>
 
void func(void) {
  FILE *fp;
 
  if (tmpfile_s(&fp)) {
    /* Handle error */
  }
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
 
extern int secure_dir(const char *sdn);
 
void func(void) {
  const char *sdn = "/home/usr1/";
  char sfn[] = "/home/usr1/temp-XXXXXX";
  FILE *sfp;

  if (!secure_dir(sdn)) {
    /* Handle error */
  }

  int fd = mkstemp(sfn);
  if (fd == -1) {
    /* Handle error */
  }

  /*
 * Unlink immediately to hide the file name.
 * The race
     condition here is inconsequential if the file
 * is created
     with exclusive permissions (glibc >= 2.0.7)
. */

  if (unlink(sfn) == -1) {
    /* Handle error */
  }

  sfp = fdopen(fd, "w+");
  if (sfp == NULL) {
    close(fd);
    /* Handle error */
  }

  /* Use temporary file. */

  fclose(sfp); /* alsoAlso closes fd. */
}