3 ms·
This is still too simplistic. Think along the lines of: void foo(T *p) { if (!p) abort(); bar(p); } void bar(T *p) { use(*p);
by atq2119 5y ago
This is still too simplistic. Think along the lines of:
void foo(T *p) {
if (!p) abort();
bar(p);
}
void bar(T *p) {
use(*p);
MACRO(p);
}
In other words, the first null-check and the latter check are in different functions that may not even be in the same compilation unit, or where the call sequence is hard to reason about due to function pointers etc.
- a1369209993 5y agoAssuming bar isn't inlined (eg separate compilation unit, as you mentioned), the null check in MACRO is not unnecessary, because bar can be called from places other than foo, and those places might pass null pointer. This is one of several situations where it might be useful for the compiler to excercise it's perogative to implement operations without regard for undefined behaviour to rewrite `use(*p);` as `if(!p) abort(); use(*p);`, which would make the null check in MACRO unnecessary, but unless it does so, the check is not unnecessary, just insufficient.