#include <atomic>#include <iostream> void print(int* val){std::cout<<*val<<std::endl;} void print2(int* val[[carries_dependency]]){std::cout<<*val<<std::endl;} int main(){int x{42};std::atomic<int*> p=&x;int* local= p.load(std::memory_order_consume); if(local){// The dependency is explicit, so the compiler knows that local is// dereferenced, and that it must ensure that the dependency chain// is preserved in order to avoid a fence (on some architectures).std::cout<<*local<<std::endl;} if(local){// The definition of print is opaque (assuming it is not inlined),// so the compiler must issue a fence in order to ensure that// reading *p in print returns the correct value.        print(local);} if(local){// The compiler can assume that although print2 is also opaque then// the dependency from the parameter to the dereferenced value is// preserved in the instruction stream, and no fence is necessary (on// some architectures). Obviously, the definition of print2 must actually// preserve this dependency, so the attribute will also impact the// generated code for print2.        print2(local);}}

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