The BMesh code relies heavily on alloca which can cause problems when the required space exceeds the reserved space.

This caused the file on T94760 to crash when a polygon with a huge number of sides enters edit mode.

As stated by @Jesse Yurkovich (deadpin) in T94760#1292932:

It's crashing on a call to BLI_array_alloca which allocates memory on the stack. An incoming mesh has mp->totloop of 98658 which causes 2 significant stack allocations of size 789264 bytes each to occur. So you are probably running out of stack space (as alluded to in the ___chkstk_darwin above).

One solution would be to always use malloc in bm_face_create_from_mpoly. But to avoid penalties in performanse, a stack for polygons of up to 64 sides is reserved.