https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125403
Bug ID: 125403
Summary: ICE with contract postcondition on in-class defaulted
constructor
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
The following valid C++26 code triggers an internal compiler error when
compiling with GCC contracts enabled.
Source:
```cpp
struct Foo {
Foo()
post(empty())
= default;
bool empty() const { return ptr == nullptr; }
int* ptr = nullptr;
};
void f() {
Foo f;
}
```
Compiler invocation: `g++ -std=c++26 repro.cpp`
Observed behavior:
GCC ICEs during compilation.
Expected behavior:
The program should compile successfully.
Compiler Explorer repro: https://godbolt.org/z/64j3acYr7
Observed with:
* GCC 15.2 + `-fcontracts`
* GCC 16.1
* GCC trunk
Does not reproduce with: Clang contracts branch
Workarounds:
1. Removing the contract:
```cpp
Foo() = default;
```
2. Using a user-provided constructor body:
```cpp
Foo() post(empty()) {}
```
3. Defaulting the constructor out-of-line:
```cpp
struct Foo {
Foo() post(empty());
~~~
};
Foo::Foo() = default;
```
Notes:
The issue appears specifically related to an in-class defaulted constructor
with a contract postcondition.
The code appears well-defined because the postcondition is evaluated after
object construction completes and after `ptr` has been initialized.
Please see CE link for ICE output and stack trace.
