blake3 compiler warnings

[dlegaultbbry]

Hello,

I see these warnings when using the new code and compiling for arm/aarch64 (I'm porting blake3 to openssl locally).

../../dist/crypto/blake3/blake3.c:264:8: warning: no previous prototype for 'blake3_compress_subtree_wide' [-Wmissing-prototypes]
size_t blake3_compress_subtree_wide(const uint8_t *input, size_t input_len,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_dispatch.c:292:8: warning: no previous prototype for 'blake3_simd_degree' [-Wmissing-prototypes]
size_t blake3_simd_degree() {
^~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_dispatch.c:153:5: warning: 'get_cpu_features' defined but not used [-Wunused-function]
get_cpu_features() {
^~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_portable.c:97:6: warning: no previous prototype for 'blake3_compress_in_place_portable' [-Wmissing-prototypes]
void blake3_compress_in_place_portable(uint32_t cv[8],
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_portable.c:113:6: warning: no previous prototype for 'blake3_compress_xof_portable' [-Wmissing-prototypes]
void blake3_compress_xof_portable(const uint32_t cv[8],
^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_portable.c:158:6: warning: no previous prototype for 'blake3_hash_many_portable' [-Wmissing-prototypes]
void blake3_hash_many_portable(const uint8_t *const *inputs, size_t num_inputs,
^~~~~~~~~~~~~~~~~~~~~~~~~
In function 'compress_parents_parallel',
inlined from 'compress_subtree_to_parent_node' at ../../dist/crypto/blake3/blake3.c:349:9,
inlined from 'blake3_hasher_update.part.0' at ../../dist/crypto/blake3/blake3.c:522:7:
../../dist/crypto/blake3/blake3.c:238:5: warning: 'memcpy' forming offset [33, 64] is out of the bounds [0, 32] of object 'out_array' with type 'uint8_t[32]' {aka 'unsigned char[32]'} [-Warray-bounds]
memcpy(&out[parents_array_len * BLAKE3_OUT_LEN],
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
&child_chaining_values[2 * parents_array_len * BLAKE3_OUT_LEN],
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BLAKE3_OUT_LEN);
~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3.c: In function 'blake3_hasher_update.part.0':
../../dist/crypto/blake3/blake3.c:346:11: note: 'out_array' declared here
uint8_t out_array[MAX_SIMD_DEGREE_OR_2 * BLAKE3_OUT_LEN / 2];
^~~~~~~~~
In function 'compress_subtree_to_parent_node',
inlined from 'blake3_hasher_update.part.0' at ../../dist/crypto/blake3/blake3.c:522:7:
../../dist/crypto/blake3/blake3.c:350:5: warning: 'memcpy' forming offset [33, 64] is out of the bounds [0, 32] of object 'out_array' with type 'uint8_t[32]' {aka 'unsigned char[32]'} [-Warray-bounds]
memcpy(cv_array, out_array, num_cvs * BLAKE3_OUT_LEN);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3.c: In function 'blake3_hasher_update.part.0':
../../dist/crypto/blake3/blake3.c:346:11: note: 'out_array' declared here
uint8_t out_array[MAX_SIMD_DEGREE_OR_2 * BLAKE3_OUT_LEN / 2];
^~~~~~~~~
In function 'compress_subtree_to_parent_node',
inlined from 'blake3_hasher_update.part.0' at ../../dist/crypto/blake3/blake3.c:522:7:
../../dist/crypto/blake3/blake3.c:350:5: warning: 'memcpy' forming offset [33, 64] is out of the bounds [0, 32] of object 'out_array' with type 'uint8_t[32]' {aka 'unsigned char[32]'} [-Warray-bounds]
memcpy(cv_array, out_array, num_cvs * BLAKE3_OUT_LEN);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3.c: In function 'blake3_hasher_update.part.0':
../../dist/crypto/blake3/blake3.c:346:11: note: 'out_array' declared here
uint8_t out_array[MAX_SIMD_DEGREE_OR_2 * BLAKE3_OUT_LEN / 2];
^~~~~~~~~
In function 'compress_parents_parallel',
inlined from 'compress_subtree_to_parent_node' at ../../dist/crypto/blake3/blake3.c:349:9,
inlined from 'blake3_hasher_update.part.0' at ../../dist/crypto/blake3/blake3.c:522:7:
../../dist/crypto/blake3/blake3.c:238:5: warning: 'memcpy' offset 64 is out of the bounds [0, 32] of object 'out_array' with type 'uint8_t[32]' {aka 'unsigned char[32]'} [-Warray-bounds]
memcpy(&out[parents_array_len * BLAKE3_OUT_LEN],
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
&child_chaining_values[2 * parents_array_len * BLAKE3_OUT_LEN],
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BLAKE3_OUT_LEN);
~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3.c: In function 'blake3_hasher_update.part.0':
../../dist/crypto/blake3/blake3.c:346:11: note: 'out_array' declared here
uint8_t out_array[MAX_SIMD_DEGREE_OR_2 * BLAKE3_OUT_LEN / 2];
^~~~~~~~~
In function 'compress_subtree_to_parent_node',
inlined from 'blake3_hasher_update.part.0' at ../../dist/crypto/blake3/blake3.c:522:7:
../../dist/crypto/blake3/blake3.c:350:5: warning: 'memcpy' forming offset [33, 96] is out of the bounds [0, 32] of object 'out_array' with type 'uint8_t[32]' {aka 'unsigned char[32]'} [-Warray-bounds]
memcpy(cv_array, out_array, num_cvs * BLAKE3_OUT_LEN);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3.c: In function 'blake3_hasher_update.part.0':
../../dist/crypto/blake3/blake3.c:346:11: note: 'out_array' declared here
uint8_t out_array[MAX_SIMD_DEGREE_OR_2 * BLAKE3_OUT_LEN / 2];
^~~~~~~~~
../../dist/crypto/blake3/blake3_neon.c:231:6: warning: no previous prototype for 'blake3_hash4_neon' [-Wmissing-prototypes]
void blake3_hash4_neon(const uint8_t *const *inputs, size_t blocks,
^~~~~~~~~~~~~~~~~
../../dist/crypto/blake3/blake3_neon.c:326:6: warning: no previous prototype for 'blake3_hash_many_neon' [-Wmissing-prototypes]
void blake3_hash_many_neon(const uint8_t *const *inputs, size_t num_inputs,
^~~~~~~~~~~~~~~~~~~~~

[oconnor663]

I'm porting blake3 to openssl locally

Sounds exciting!

'memcpy' forming offset [33, 64] is out of the bounds [0, 32] of object 'out_array'

I have definitely seen that one before, and I have a hard time understanding what's causing it. Is it possible it's a bug in the compiler? The make test C tests turn on ASan, so I don't think we're doing anything grossly unsafe, and the C code is also a direct port of some safe Rust code. Maybe the compiler doesn't understand that the if-statement at the end of compress_parents_parallel can't execute in the case where the function has already totally filled its out array?

[dlegaultbbry]

It was because -DBLAKE3_USE_NEON was not defined for all source files compiled for arm/aarch64 so the array size varied wildly between compilation units. Initially I had it only for the neon file before moving it to the others.

[oconnor663]

I'm going to reopen this, because I've definitely made that mistake myself, and I want to make sure I fully understand the warning.