https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71448
Bug ID: 71448
Summary: pointer relational comparison fails inside constant
expression
Product: gcc
Version: 5.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at adamsimpkins dot net
Target Milestone: ---
Created attachment 38656
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38656&action=edit
Simple repro code
Comparing two pointers with less than/greater than fails inside a constant
expression when compiling without optimization enabled. Failing code:
static constexpr const char foo[] = "foo";
static constexpr const char* bar = "bar";
static_assert((foo + 3 - foo) == 3, "check"); // Works
static_assert(foo + 2 != foo, "check"); // Works
static_assert(foo + 2 >= foo, "check"); // Works
static_assert(foo + 3 >= foo, "check"); // Works
static_assert((bar + 3 - bar) == 3, "check"); // Works
static_assert(bar + 2 != bar, "check"); // Works
static_assert(bar + 2 >= bar, "check"); // Compile error without -O2
static_assert(bar + 3 >= bar, "check"); // Compile error without -O2
This seems very similar to bug #67376, but not quite the same.
As best I can tell from reading the standard, this pointer arithmetic is
defined, so this seems like it should be a valid constant expression.
When compiling with -O2 or -O3 the code compiles correctly, and static_assert
checks pass/fail as expected.
I've confirmed this behavior with gcc 4.9 (built from r221427) and gcc 5.3
(built from r233903).
