I have this piece of code:
clang give this warning: implicit use of sequentially-consistent atomic may incur stronger memory barriers than necessary.Code:atomic_int Vector[2]; void Load(int *v) { v[0]=atomic_load(&Vector[0]); v[1]=atomic_load(&Vector[1]); } void Store(int *v) { atomic_store(&Vector[0],v[0]); atomic_store(&Vector[1],v[1]); }
How can this warning be solved?
You need to be more specific.
I tried this over on Compiler Explorer for several versions of clang with several sets of flags and saw nothing unusual.Code:#include <stdatomic.h> atomic_int Vector[2]; void Load(int *v) { v[0]=atomic_load(&Vector[0]); v[1]=atomic_load(&Vector[1]); } void Store(int *v) { atomic_store(&Vector[0],v[0]); atomic_store(&Vector[1],v[1]); } int main() { return 0; }
State:
- your actual clang version
- your actual compiler command line
- your actual compilable program (not some snippet)
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Ok, this is the code for compiler explorer try with flag -Weverything
Code:#include <stdatomic.h> typedef struct { atomic_ullong V[2]; } vector_t; vector_t *Vector; void Load(int index,vector_t *vec) { vec->V[0] = atomic_load(&Vector[index].V[0]); vec->V[1] = atomic_load(&Vector[index].V[1]); vec->V[0]^=vec->V[1]; } void Store(int index,vector_t *vec) { vec->V[0]^=vec->V[1]; atomic_store(&Vector[index].V[0],vec->V[0]); atomic_store(&Vector[index].V[1],vec->V[1]); }
I have solved in this way:
I'm sorry for the question.Code:#include <stdatomic.h> typedef struct { atomic_ullong V[2]; } vectoratomic_t; typedef struct { unsigned long long int V[2]; } vector_t; vectoratomic_t *Vector; void Load(int index,vector_t *vec) { vec->V[0] = atomic_load(&Vector[index].V[0]); vec->V[1] = atomic_load(&Vector[index].V[1]); vec->V[0]^=vec->V[1]; } void Store(int index,vector_t *vec) { vec->V[0]^=vec->V[1]; atomic_store(&Vector[index].V[0],vec->V[0]); atomic_store(&Vector[index].V[1],vec->V[1]); }
