First Experiments with C++26 Contracts (and a GCC Crash)

I have recently been working on a hazard pointer implementation for libstdc++ - more posts on that are coming soon - and decided to experiment with the upcoming C++26 contracts support along the way.

Unfortunately, my very first attempt immediately triggered a GCC crash.

The issue appears when attaching a post() condition to a defaulted in-class constructor:

class Foo {
    Foo() post(true) = default;
};

GCC crashes during compilation instead of producing a diagnostic.

Since compiler crashes are always worth reporting, I filed a bug report on the GCC Bugzilla tracker as well: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125403

It is still early days for contracts support, so rough edges are expected, but hitting an ICE on the very first experiment raises concerns.