I had already opened a bpo issue here for this : https://bugs.python.org/issue37732 for someone to investigate. Please link to it in this PR title.
i.e

bpo-37732 : Fix unintialized pointer warning in Objects/obmalloc.c

Thanks @nanjekyejoannah, I will link this PR with opened bpo issue. And also move this PR from draft to open state.

Why no warning in _PyObject_Calloc?

Why no warning in _PyObject_Calloc?

This is because in _PyObject_Calloc memory is initialized using memset but in case of _PyObject_Malloc memory is just allocated and returned(no initialization is done). If we remove memset statement from _PyObject_Calloc we will get the same pointer uninitialized warning for _PyObject_Calloc also. I have verified this.

This is another PR #15293 where Victor suggested that _PyObject_Malloc was intentionally designed to return uninitialized memory so we can't use memset here to fix this warning so I have just initialized ptr with NULL pointer to fix this warning. Please guide me if we can do anythig better to fix this warning.

It seems that warning was introduced by bpo-37543: optimize pymalloc (#14674

Why does this warning appear after using 'LIKELY'?

• bpo-37543: optimize pymalloc #14674
• fb26504#diff-c078b6b7dd8dc2125fb4d48f7020b796

And maybe we can resue _PyObject_Malloc in _PyObject_Calloc.

I dislike this change since it adds an useless initialization to NULL, ptr is already always initialized: GCC is just wrong. I wrote PR #15333 to fix the warning without adding an useless initialization.

_PyObject_Malloc() function is performance critical so I would prefer to not make it slower ;-)

Close: I merged my PR #15333 instead.

@hansrajdas: but thanks for your contribution anyway ;-)

Thanks @vstinner for your guidance, It was good learning for me following your PR #15333 :)