Tried to address #4, but the bug is still in place

src/main.c

@@ -105,7 +105,12 @@ int main (int argc,char** argv)
   off_t fsize = (off_t)(sizeof(uint64_t))*args.re_size*args.im_size;
   int files[l];
   uint64_t *maps[l];
-
+  uint64_t *zeros=calloc(args.re_size,sizeof(uint64_t)); /* String full of zeros, to write into new files in batches */
+  if(!zeros)
+  {
+    fprintf(stderr,"Can't create a string full of zeros, quitting\n");
+    return(1);    
+  }        
   for(int i=0; i<l; i++)
     {
       char fname[STR_MAXLEN];
@@ -120,7 +125,6 @@ int main (int argc,char** argv)
 	{
 	  /* Create file */
 	  files[i]=open(fpath,O_RDWR|O_CREAT,S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
-	  uint64_t *zeros=calloc(args.re_size,sizeof(uint64_t)); /* Get string full of zeros, to write into file in batches */
 	  for(uint64_t x=0;x<args.re_size;x++)
 	    {
 	      if(-write(files[i],zeros,args.im_size*sizeof(uint64_t))==-1) /* Create file of the right size, full of zeros */
@@ -131,7 +135,6 @@ int main (int argc,char** argv)
 		  return(1);
 		}
 	    }
-	  free(zeros);
 	  if(v)
 	    fprintf(stdout,"created.\n");
 	  close(files[i]);
@@ -165,14 +168,14 @@ int main (int argc,char** argv)
 	  return(1);
 	}
       /* Finally, when the file is ready, map it to memory */
-      if(!(maps[i]=mmap(NULL,fsize,PROT_READ|PROT_WRITE,MAP_SHARED,files[i],0)))
+      if((maps[i]=mmap(NULL,fsize,PROT_READ|PROT_WRITE,MAP_SHARED,files[i],0))==MAP_FAILED)
 	{
-	  fprintf(stderr,"Can't create mapping\n");
+	  fprintf(stderr,"Can't create mapping, quitting\n");
 	  return(1);
 	}
       madvise(maps[i],fsize,MADV_RANDOM);
     }
-
+  free(zeros);
   /* Now, everything is ready. Let's roll! */
 
   /* Create threads */

src/worker.c

@@ -20,6 +20,11 @@ void* worker(void *arg_v)
 
   /* Create thread-local buffer */
   uint64_t **buff=malloc(arg->re_size*sizeof(uint64_t*));
+  if(!buff)
+    {
+      fprintf(stderr,"Can't allocate space for buffer array\n");
+      exit(1);
+    }
   for(uint32_t x=0;x<arg->re_size;x++)
     {
       buff[x]=calloc(arg->im_size,sizeof(uint64_t));
@@ -29,6 +34,14 @@ void* worker(void *arg_v)
 	  exit(1);
 	}
     }
+
+  /* Keep track of which rows were written to */
+  uint8_t *dirty_rows=calloc(arg->re_size,sizeof(uint8_t));
+  if(!dirty_rows)
+    {
+      fprintf(stderr,"Can't allocate space for dirty rows marker, quitting\n");
+      exit(1);
+    }
 
   /* Run until number of runs is reached */
   while(1)
@@ -90,8 +103,7 @@ void* worker(void *arg_v)
       while(inside==1);
 
       int64_t idx_x,idx_y; /* buff (2D array) coords */
-      uint8_t dirty_rows[arg->re_size];
-      for(uint32_t i=0;i< arg->re_size ;dirty_rows[i++]=0); /*zero dirty rows */
+
       /* Now we have a point which is outside, can iterate and draw */
       Z=c;
       uint64_t i;
@@ -132,10 +144,17 @@ void* worker(void *arg_v)
       	}
       pthread_mutex_unlock(&arg->locks[k]);
 
-      for(uint32_t x=0;x<arg->re_size;x++)for(uint32_t y=0;y<arg->im_size;y++)
-					    {
-					      buff[x][y]=0;
-					    }
+      for(uint32_t x=0;x< arg->re_size;x++)
+        {
+      	  if(dirty_rows[x])
+	    {
+	      for(uint32_t y=0;y< arg->im_size;y++)
+		{
+		  buff[x][y]=0;
+		}
+	      dirty_rows[x]=0;
+	    }
+      	}
 
     }
 }