Net code contains some UB – violations of strict aliasing rules in C++ #22613

1. 
   cculianu commented at 0:01 am on August 3, 2021: none

   Expected behavior

   No undefined behavior in bitcoin’s C++ code.

   However, the Bitcoin code does contain UB in the net code in particular. All of the code that works with struct sockaddr needs to be inspected and fixed. For example here: https://github.com/bitcoin/bitcoin/blob/b620b2d58a55a88ad21da70cb2000863ef17b651/src/netaddress.cpp#L988

   It is illegal/UB in C++ to do this type of aliasing and dereference a pointer that is reinterpre_casted in this way. C++ has stricter aliasing rules than C. For reference, see this: https://en.cppreference.com/w/cpp/language/reinterpret_cast#Type_aliasing

   Suggested Fix

   Use std::memcpy to copy the structs around and dereference them after copying them.

2. cculianu added the label Bug on Aug 3, 2021
3. cculianu renamed this:
   Net code contains some UB -- violations of strict type aliasing rules in C++
   Net code contains some UB -- violations of strict aliasing rules in C++
   on Aug 3, 2021
4. MarcoFalke added the label P2P on Aug 3, 2021
5. Adlai-Holler referenced this in commit 997de28dc8 on Apr 11, 2022
6. Adlai-Holler referenced this in commit f488d2e3da on Apr 11, 2022
7. Adlai-Holler referenced this in commit 77f0208cf9 on Apr 11, 2022
8. Adlai-Holler referenced this in commit bc21a2b0df on Apr 15, 2022
9. Adlai-Holler referenced this in commit d6466e889f on May 3, 2022
10. Adlai-Holler referenced this in commit 0b3ad72146 on May 3, 2022

Contributors
cculianu

Labels
Bug P2P