3.13 AIX build static asserts fails '(sizeof(_PyCallCache) / sizeof(_Py_CODEUNIT)) == 3': incorrect cache size

[rsmkaminskas]

Bug report

Bug description:

Python fails to build after starting make on AIX machines by failing asserts in many places

In file included from Python/ceval.c:782:
Python/generated_cases.c.h:2041:27: error: static assertion failed due to requirement '(sizeof(_PyCallCache) / sizeof(_Py_CODEUNIT)) == 3': incorrect cache size
 2041 |             static_assert(INLINE_CACHE_ENTRIES_CALL == 3, "incorrect cache size");
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./Include/internal/pycore_code.h:157:35: note: expanded from macro 'INLINE_CACHE_ENTRIES_CALL'
  157 | #define INLINE_CACHE_ENTRIES_CALL CACHE_ENTRIES(_PyCallCache)
      |                                   ^
./Include/internal/pycore_code.h:88:30: note: expanded from macro 'CACHE_ENTRIES'
   88 | #define CACHE_ENTRIES(cache) (sizeof(cache)/sizeof(_Py_CODEUNIT))
      |                              ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

I am just pasting the last failed assert, when the build stops. It seems that the data types' sizes do not match on the AIX machine.

CPython versions tested on:

3.13

Operating systems tested on:

Other

[picnixz]

cc @brandtbucher as the one who added those static assertions initially (b4978ff) and @markshannon who had the latest changes on those lines (b449415).

[srinivasreddy]

I am curious, don't we have AIX buildbot? I never seen one.

[rsmkaminskas]

I found that https://github.com/python/cpython/pull/124469/files#diff-2772c99555ca0a4a3987e20582200c6eb6314fea3e5f3a5f7f2cbc2e371e22adR18 these changes prevent this assert from failing on current main branch.

While these changes helped me to build Python locally.

./Include/internal/pycore_code.h
 
+ #pragma pack(push, 1) // Set alignment to 1 byte
typedef union {
    uint16_t cache;
    struct {
        uint8_t code;
        uint8_t arg;
    } op;
    _Py_BackoffCounter counter;  // First cache entry of specializable op
} _Py_CODEUNIT;
+ #pragma pack(pop) // Restore original alignment

./Include/internal/pycore_backoff.h
 
+ #pragma pack(push, 1) // Set alignment to 1 byte
typedef struct {
    union {
        struct {
            uint16_t backoff : 4;
            uint16_t value : 12;
        };
        uint16_t as_counter;  // For printf("%#x", ...)
    };
} _Py_BackoffCounter;
+ #pragma pack(pop) // Restore original alignment

I am not sure if it's still relevant to make PR with these changes since it's been kind of fixed in the former changes.

[Ganeshkumhar1]

I am hitting same issue on AIX build . Is there any fix available for this?

Python/generated_cases.c.h:854:27: error: static assertion failed due to requirement '(sizeof(_PyCallCache) / sizeof(_Py_CODEUNIT)) == 3': incorrect cache size
  854 |             static_assert(INLINE_CACHE_ENTRIES_CALL == 3, "incorrect cache size");

[rsmkaminskas]

Yes, the above changes helped me.