In FLE2RangeFindDriverSpec_to_ciphertexts in mongocrypt-ctx-encrypt.c, a Valgrind memory leak can occur when the libbson BSON_MEMCHECK compile flag is set because:

• bson_t with_placholders is initialized on line 1730 (as of commit 2ec9c3) with BSON_INITIALIZER
• The function calls mc_FLE2RangeFindDriverSpec_to_placeholders on line 1768 and passes with_placholders as the out argument.
• mc_FLE2RangeFindDriverSpec_to_placeholders calls bson_init on out on line 508

One possible solution is to remove the extra call to bson_init within the mc_FLE2RangeFindDriverSpec_to_placeholders function. Note that there is a test case in test-mc-fle2-rfds.c that uses mc_FLE2RangeFindDriverSpec_to_placeholders and the out argument passed to that test function will need to be initialized if this change is made.

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To reproduce the memory leak, use

mkdir cmake-build && cd cmake-build
cmake ../
make
valgrind --leak-check=full ./test-mongocrypt