Re:Git's list of banned C functions
by kiwidrew on Thursday March 04, 2021 @07:00PM
(#26350324)
Ah, indeed! Thanks for the link.
I think many of the "safe C" variants get tripped up by starting with fat pointers (length + pointer as an atomic value) and then have trouble (rightly so!) when trying to squeeze them through the C standard ABI; it's a square peg in round hole sort of situation.
The key observation from WalterBright's post is that the C standard ABI already has a way to pass fat pointers, using a pair of arguments (size_t and char *) in an ad-hoc manner.
It's the not-useful-but-legal C99 VLA declaration in the function prototype that could, if one is willing to violate the C99 spec, allow a compiler to automatically derive a fat pointer inside the body of a function in a manner that is backwards-compatible with the C standard ABI.
I think many of the "safe C" variants get tripped up by starting with fat pointers (length + pointer as an atomic value) and then have trouble (rightly so!) when trying to squeeze them through the C standard ABI; it's a square peg in round hole sort of situation.
The key observation from WalterBright's post is that the C standard ABI already has a way to pass fat pointers, using a pair of arguments (size_t and char *) in an ad-hoc manner.
It's the not-useful-but-legal C99 VLA declaration in the function prototype that could, if one is willing to violate the C99 spec, allow a compiler to automatically derive a fat pointer inside the body of a function in a manner that is backwards-compatible with the C standard ABI.