...
Using the same class definitions as the noncompliant code example, this compliant solution modifies the definition of f()
to require raw pointers to the object, removing the slicing problem:.
Code Block | ||||
---|---|---|---|---|
| ||||
// Remainder of code unchanged... void f(const Employee *e) { if (e) { std::cout << *e; } } int main() { Employee coder("Joe Smith"); Employee typist("Bill Jones"); Manager designer("Jane Doe", typist); f(&coder); f(&typist); f(&designer); } |
This compliant solution also complies with EXP34-C. Do not dereference null pointers in the implementation of f()
. With this definition, the the program correctly outputs :the following.
Code Block |
---|
Employee: Joe Smith Employee: Bill Jones Manager: Jane Doe Assistant: Employee: Bill Jones |
...
An improved compliant solution, which does not require guarding against null pointers within f()
, uses references instead of pointers:.
Code Block | ||||
---|---|---|---|---|
| ||||
// ... Remainder of code unchanged ... void f(const Employee &e) { std::cout << e; } int main() { Employee coder("Joe Smith"); Employee typist("Bill Jones"); Manager designer("Jane Doe", typist); f(coder); f(typist); f(designer); } |
...
This compliant solution uses a vector of std::unique_ptr
objects, which eliminates the slicing problem:.
Code Block | ||||
---|---|---|---|---|
| ||||
#include <iostream> #include <memory> #include <string> #include <vector> void f(const std::vector<std::unique_ptr<Employee>> &v) { for (const auto &e : v) { std::cout << *e; } } int main() { std::vector<std::unique_ptr<Employee>> v; v.emplace_back(new Employee("Joe Smith")); v.emplace_back(new Employee("Bill Jones")); v.emplace_back(new Manager("Jane Doe", *v.front())); f(v); } |
...
Slicing results in information loss, which could lead to abnormal program execution or denial-of-service attacks.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
---|---|---|---|---|---|
OOP51-CPP | Low | Probable | Medium | P4 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
---|---|---|---|---|---|---|---|---|---|
CodeSonar |
| LANG.CAST.OBJSLICE | Object Slicing | ||||||
Helix QAC |
| C++3072 | |||||||
Parasoft C/C++test |
3072, 3073
| CERT_CPP-OOP51-a | Avoid slicing function arguments / return value | |||||||
Polyspace Bug Finder |
| CERT C++: OOP51-CPP | Checks for object slicing (rule partially covered) | ||||||
PVS-Studio |
| V1054 |
Related Vulnerabilities
Search for other vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
SEI CERT C++ Coding Standard | ERR61-CPP. Catch exceptions by lvalue reference |
SEI CERT C Coding Standard |
Bibliography
[Dewhurst |
2002] | Gotcha #38, "Slicing" |
[ISO/IEC 14882-2014] | Subclause 12.8, "Copying and Moving Class Objects" |
[Sutter |
2000] | Item 40, "Object Lifetimes—Part I" |
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