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Overview
Comment:Update the showlocks utility program so that it functions on files with a huge number of locks without overflowing the stack.
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SHA3-256: adb7484f93329c7a94cd84e30bc4a8dbf2d6e901eba17cc3454afb8ba346cbf4
User & Date: drh 2020-06-25 23:21:09
Context
2020-06-26
04:34
Fix a possible null pointer deref following OOM. Discovered by dbsqlfuzz. (check-in: cc888878ea user: drh tags: trunk)
2020-06-25
23:21
Update the showlocks utility program so that it functions on files with a huge number of locks without overflowing the stack. (check-in: adb7484f93 user: drh tags: trunk)
2020-06-24
15:06
Add the ieee754_mantissa() and ieee754_exponent() functions to the iee754 extension. Build the ieee754 extension into the CLI. (check-in: db2f0836b6 user: drh tags: trunk)
Changes
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Changes to tool/showlocks.c.

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/*
** Print all locks on the inode of "fd" that occur in between
** lwr and upr, inclusive.
*/
static int showLocksInRange(int fd, off_t lwr, off_t upr){
  int cnt = 0;
  struct flock x;





















  x.l_type = F_WRLCK;
  x.l_whence = SEEK_SET;
  x.l_start = lwr;
  x.l_len = upr-lwr;
  fcntl(fd, F_GETLK, &x);
  if( x.l_type==F_UNLCK ) return 0;
  printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
       (int)x.l_start, (int)x.l_len,
       x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
  cnt++;









  if( x.l_start>lwr ){
    cnt += showLocksInRange(fd, lwr, x.l_start-1);



  }
  if( x.l_start+x.l_len<upr ){
    cnt += showLocksInRange(fd, x.l_start+x.l_len+1, upr);



  }


  return cnt;
}

int main(int argc, char **argv){
  int fd;
  int cnt;








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/*
** Print all locks on the inode of "fd" that occur in between
** lwr and upr, inclusive.
*/
static int showLocksInRange(int fd, off_t lwr, off_t upr){
  int cnt = 0;
  struct flock x;
  struct lockRange {
    off_t lwr;
    off_t upr;
  } *aPending = 0;
  int nAlloc = 1;
  int nPending = 0;
  int nDone = 0;

  nPending = 1;
  aPending = malloc( sizeof(aPending[0]) );
  if( aPending==0 ){
    fprintf(stderr, "out of memory\n");
    exit(1);
  }
  aPending[0].lwr = lwr;
  aPending[0].upr = upr;

  for(nDone=0; nDone<nPending; nDone++){
    lwr = aPending[nDone].lwr;
    upr = aPending[nDone].upr;
    if( lwr>=upr ) continue;
    x.l_type = F_WRLCK;
    x.l_whence = SEEK_SET;
    x.l_start = lwr;
    x.l_len = upr - lwr;
    fcntl(fd, F_GETLK, &x);
    if( x.l_type==F_UNLCK ) continue;
    printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
         (int)x.l_start, (int)x.l_len,
         x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
    cnt++;
    if( nPending+2 > nAlloc ){
      nAlloc = nAlloc*2 + 2;
      aPending = realloc(aPending, sizeof(aPending[0])*nAlloc );
    }
    if( aPending==0 ){
      fprintf(stderr, "unable to realloc for %d bytes\n",
                      (int)sizeof(aPending[0])*(nPending+2));
      exit(1);
    }
    if( lwr<x.l_start ){

      aPending[nPending].lwr = lwr;
      aPending[nPending].upr = x.l_start;
      nPending++;
    }
    if( x.l_start+x.l_len<=upr ){

      aPending[nPending].lwr = x.l_start + x.l_len;
      aPending[nPending].upr = upr;
      nPending++;
    }
  }
  free(aPending);
  return cnt;
}

int main(int argc, char **argv){
  int fd;
  int cnt;