https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89533
Bug ID: 89533
Summary: G++ incorrectly generates noexcept assignment operator
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: alexey.kutumov at gmail dot com
Target Milestone: ---
Created attachment 45852
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45852&action=edit
minimal sample which reproduces problem
Consider following example (bad.cpp in atttachment). In this example i have
struct VectorWrapper with following assignment operator:
VectorWrapper& operator=(VectorWrapper) noexcept {
return *this;
}
Which is really noexcept
And copy ctor:
VectorWrapper(const VectorWrapper& ){
throw 42;
}
Which is *not* noexcept
If i wrap this struct into
struct MyData {
VectorWrapper vec;
};
And tries to copy one instance of MyData into another my program crashes even
if i try to catch exception (as seen in bad.cpp).
I suppose that compiler marks assignment operator of MyData as *noexcept* while
it actually is *NOT* noexcept, because it calls copy ctor of VectorWrapper.
I've filed same bug to MSVC:
https://developercommunity.visualstudio.com/content/problem/456988/program-crashes-while-throwing-exception-inside-ge.html?childToView=470086#comment-470086
They said that there is a bug in implementation:
For reference, here's what the Standard has to say:
The exception specification for an implicitly-declared assignment operator, or
an assignment-operator without a noexcept-specifier that is defaulted on its
first declaration, is potentially-throwing if and only if the invocation of any
assignment operator in the implicit definition is potentially-throwing
http://eel.is/c++draft/except.spec#9
Our interpretation of "invocation of any assignment operator" includes the
argument conversions required, not just the specific function(s) being called.
This wording changed quite a bit since C++14, where it explicitly called out
"any function it directly invokes" which would more obviously include the copy
constructor call, yet still no compiler I tried implemented this.
