Re:The Lost Art of Structure Packing (2018)
by saagarjha on Tuesday April 28, 2020 @01:19AM
(#23003660)
…and assigning to a variable is supposed to put some bytes at a certain address, yes. Except compilers will skip doing so if you never read from the variable again, and the same thing happens here: the compiler can "know" that it has no need to actually do the assignment, as writing to padding bytes is not required to actually do anything and trying to observe the value is currently the subject of debate but somewhere between "undefined" and "whatever you get out of it has nothing to do with what you think went in".
There is no need for a broken memset that fails to set some of the bytes, so that a fixed one under a different name has to be used in its place.
If you're using memset such that it's okay for memset not to set some of the bytes, and you'd like them not to be set if that makes things faster, then you shouldn't be using memset. You're using a hammer to drive a screw: wrong tool.
C has perfectly good initialization and assignment for structures.
End of story; I'm going to walk away pretend I never read this subthread, re-joining the hordes of C programmers using memset in the normal way, adding to the countless lines of code that do it that way and are never going to be changed.
This bullshit will be backpedaled out of the standard eventually, you just wait.