commit 8dadc362046281e7a19cc161ddc45d2de5e6a8df
Author: Peter Williams <peter@newton.cx>
Date:   Sun Oct 23 16:45:08 2022 +0000

    In memleak test, track reallocs of startup pointers (#7379)
    
    The conda-forge build of this package was encountering test failures
    because their Windows build configuration involves a situation where
    some of the tests cause a realloc of memory in the memleak test's
    `start_heap`. Here we allow such reallocs and do not count them as
    leaks if they do not add too much memory usage, where "too much"
    is currently defined as 1024 bytes.
    
    refs #7379

diff --git a/tests/hazmat/backends/test_openssl_memleak.py b/tests/hazmat/backends/test_openssl_memleak.py
index 2605566bd..b1df39e27 100644
--- a/tests/hazmat/backends/test_openssl_memleak.py
+++ b/tests/hazmat/backends/test_openssl_memleak.py
@@ -27,6 +27,8 @@ def main(argv):
     from cryptography.hazmat.bindings._openssl import ffi, lib
 
     heap = {}
+    start_heap = {}
+    start_heap_realloc_delta = [0]  # 1-item list so callbacks can mutate it
 
     BACKTRACE_ENABLED = False
     if BACKTRACE_ENABLED:
@@ -70,6 +72,20 @@ def main(argv):
             del heap[ptr]
         new_ptr = lib.Cryptography_realloc_wrapper(ptr, size, path, line)
         heap[new_ptr] = (size, path, line, backtrace())
+
+        # It is possible that something during the test will cause a
+        # realloc of memory allocated during the startup phase. (This
+        # was observed in conda-forge Windows builds of this package with
+        # provider operation_bits pointers in crypto/provider_core.c.) If
+        # we don't pay attention to that, the realloc'ed pointer will show
+        # up as a leak; but we also don't want to allow this kind of realloc
+        # to consume large amounts of additional memory. So we track the
+        # realloc and the change in memory consumption.
+        startup_info = start_heap.pop(ptr, None)
+        if startup_info is not None:
+            start_heap[new_ptr] = heap[new_ptr]
+            start_heap_realloc_delta[0] += size - startup_info[0]
+
         return new_ptr
 
     @ffi.callback("void(void *, const char *, int)")
@@ -87,7 +103,7 @@ def main(argv):
 
     hashlib.sha256()
 
-    start_heap = set(heap)
+    start_heap.update(heap)
 
     try:
         func(*argv[1:])
@@ -113,10 +129,12 @@ def main(argv):
         )
         assert result == 1
 
-    remaining = set(heap) - start_heap
+    remaining = set(heap) - set(start_heap)
 
-    if remaining:
-        sys.stdout.write(json.dumps(dict(
+    # The constant here is the number of additional bytes of memory
+    # consumption that are allowed in reallocs of start_heap memory.
+    if remaining or start_heap_realloc_delta[0] > 1024:
+        info = dict(
             (int(ffi.cast("size_t", ptr)), {
                 "size": heap[ptr][0],
                 "path": ffi.string(heap[ptr][1]).decode(),
@@ -124,7 +142,9 @@ def main(argv):
                 "backtrace": symbolize_backtrace(heap[ptr][3]),
             })
             for ptr in remaining
-        )))
+        )
+        info["start_heap_realloc_delta"] = start_heap_realloc_delta[0]
+        sys.stdout.write(json.dumps(info))
         sys.stdout.flush()
         sys.exit(255)