https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113047
Bug ID: 113047
Summary: dereferencing a null pointer in a constant expression
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc_bz at brnz dot org
Target Milestone: ---
Should it be possible to dereference a null pointer in a C++20 constant
expression?
Consider this c++20 code:
struct T {
constexpr bool isNull() {
return !this;
}
};
static_assert(((T*)nullptr)->isNull());
constexpr T* t = nullptr;
static_assert((*t).isNull());
I would expect this to not compile due to the dereferencing of a null pointer
in a constant expression.
With reference to https://godbolt.org/z/q53rz5d69
By default, gcc-13.2 compiles without warning. -Wall yields a -Wnonnull
warning.
clang-17.0.1 produces errors and warning, by default.
msvc 19.38 compiles without warning.
Potentially relevant context:
2748. Accessing static data members via null pointer
https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2748
2823. Implicit undefined behavior when dereferencing pointers
https://cplusplus.github.io/CWG/issues/2823.html
