https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106390
Bug ID: 106390
Summary: Support gsl::owner<T> and/or [[gnu::owner]] attribute
in -fanalyzer
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Blocks: 97110
Target Milestone: ---
Check that "owned" resources are freed:
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c31-all-resources-acquired-by-a-class-must-be-released-by-the-classs-destructor
This would require the analyzer to recognize the gsl::owner alias and treat it
specially. The definition of gsl::owner is simply a typedef for a raw pointer:
template <class T, class = std::enable_if_t<std::is_pointer<T>::value>>
using owner = T;
(Reference impl at https://github.com/microsoft/GSL but I plan to add a <gsl>
header to libstdc++ too, making use of GCC extensions.)
The point is to permit static analysis to treat that pointer differently to a
non-owning pointer (which just aliases some other object that isn't owned). If
the code just uses T* it's unclear what the semantics of that member are. If it
uses gsl::owner<T*> it's explicit that the class "owns" that pointer and is
directly responsible for deallocating it.
Pointers stored as a gsl::owner must be freed in a destructor, unless ownership
has been transferred to another object via move semantics.
class S {
public:
S();
S(S&&);
~S() { } // bug! owned resource not freed
private:
struct Impl;
gsl::owner<Impl*> m_pimpl;
};
A more general solution would be a new [[gnu::owner]] attribute that can be
added to any data member to say it owns a resource. So the following would be
equivalent to the example above:
class S {
public:
S();
S(S&&);
~S() { } // bug! owned resource not freed
private:
struct Impl;
[[gnu::owner]] Impl* m_pimpl;
};
This attribute would be extensible to non-pointer types such as file
descriptors and other resources where ownership is transferred by move
constructors and freed by destructors etc.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97110
[Bug 97110] [meta-bug] tracker bug for supporting C++ in -fanalyzer
