Fix progress bar for --leaks mode

For the progress bar to work, it needs to know how many records total
will be processed, but `--leaks` mode has just been passing the largest
possible `size_t` in. To make this work as expected, expose the count of
allocations from the `ProgressIndicator`, so that we can collect it on
our first pass and update our stats based on it for use in our second
pass.

Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

src/memray/_memray.pyx

@@ -415,9 +415,9 @@ cdef class ProgressIndicator:
         return False
 
     cdef update(self, size_t n_processed):
+        self._cumulative_num_processed += n_processed
         if not self._report_progress:
             return
-        self._cumulative_num_processed += n_processed
         if self._cumulative_num_processed % self._update_interval == 0:
             if self._time_for_refresh():
                 assert(self._context_manager is not None)
@@ -426,6 +426,10 @@ cdef class ProgressIndicator:
                 )
                 self._context_manager.refresh()
 
+    @property
+    def num_processed(self):
+        return self._cumulative_num_processed
+
 
 cdef class FileReader:
     cdef cppstring _path
@@ -480,7 +484,8 @@ cdef class FileReader:
                 else:
                     break
         self._high_watermark = finder.getHighWatermark()
-
+        stats["n_allocations"] = progress_indicator.num_processed
+
     def __dealloc__(self):
         self.close()
 
@@ -547,7 +552,7 @@ cdef class FileReader:
 
     def get_leaked_allocation_records(self, merge_threads=True):
         self._ensure_not_closed()
-        cdef size_t max_records = numeric_limits[size_t].max()
+        cdef size_t max_records = self._header["stats"]["n_allocations"]
         yield from self._yield_unfreed_allocations(max_records, merge_threads)
 
     def get_allocation_records(self):