C++
clang HEAD 12.0.0 (https://github.com/llvm/llvm-project.git 035396197a5f129c5ec42e9e46a85c32fa1c1b84)
$ clang++ prog.cc -Wall -Wextra -I/opt/wandbox/boost-1.73.0/clang-head/include -std=c++2a -Wunreachable-codeprog.cc:6:9: warning: variable 'p' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (size < 256) {
^~~~~~~~~~
prog.cc:10:9: note: uninitialized use occurs here
if (p != nullptr) // C4701 and C4703
^
prog.cc:6:5: note: remove the 'if' if its condition is always true
if (size < 256) {
^~~~~~~~~~~~~~~~
prog.cc:5:12: note: initialize the variable 'p' to silence this warning
void* p;
^
= nullptr
1 warning generated.