gcc: 编译选项：-fdelete-null-pointer-checks、-fno-delete-null-pointer-checks

说明

这个说明写的有些理解不了，可能还是不太理解（有未知的东西在里面？）。但是从这个编译选项的命名上来看还是非常明确，就是删除不必要的空指针检查。使用时要小心了，这个优化超出了编译的界限！
-fdelete-null-pointer-checks
Assume that programs cannot safely dereference null pointers, and that no code or data element resides at address zero. This option enables simple constant folding optimizations at all optimization levels. In addition, other optimization
passes in GCC use this flag to control global dataflow analyses that eliminate useless checks for null pointers; these assume that a memory access to address zero always results in a trap, so that if a pointer is checked after it has already been dereferenced, it cannot be null.
Note however that in some environmen