The std::abort()
, std::quick_exit()
, and std::_Exit()
functions are used to terminate the program in an immediate fashion. They do so without calling exit handlers registered with std::atexit()
and without executing destructors for objects with automatic, thread, or static storage duration. Whether open streams with unwritten buffered data are flushed, open streams are closed, or temporary files are removed [ISO/IEC 9899:1999] is implementation defined. Because these functions can leave external resources, such as files and network communications, in an indeterminate state, they should be called explicitly only in direct response to a critical error in the application; see ERR50-CPP-EX1 for more information.
The std::terminate()
function calls the current terminate_handler
function, which defaults to calling std::abort()
.
The C++ Standard defines several ways in which std::terminate()
may be called implicitly by an implementation [ISO/IEC 14882-2014]:
- When the exception handling mechanism, after completing the initialization of the exception object but before activation of a handler for the exception, calls a function that exits via an exception. ([except.throw], paragraph 7)
- When a throw-expression with no operand attempts to rethrow an exception and no exception is being handled. ([except.throw], paragraph 9)
- When the exception handling mechanism cannot find a handler for a thrown exception. ([except.handle], paragraph 9)
- See ERR51-CPP. Handle all exceptions for more information.
- When the search for a handler encounters the outermost block of a function with a noexcept-specification that does not allow the exception. ([except.spec], paragraph 9)
- See ERR55-CPP. Honor exception specifications for more information.
- When the destruction of an object during stack unwinding terminates by throwing an exception. ([except.ctor], paragraph 3)
- See DCL57-CPP. Do not let exceptions escape from destructors or deallocation functions for more information.
- When initialization of a nonlocal variable with static or thread storage duration exits via an exception. ([basic.start.init], paragraph 6)
- See ERR58-CPP. Handle all exceptions thrown before main() begins executing for more information.
- When destruction of an object with static or thread storage duration exits via an exception. ([basic.start.term], paragraph 1)
- When execution of a function registered with
std::atexit()
orstd::at_quick_exit()
exits via an exception. ([support.start.term], paragraphs 8 and 12) - When the implementation’s default unexpected exception handler is called. ([except.unexpected], paragraph 2) Note that
std::unexpected()
is currently deprecated. - When
std::unexpected()
throws an exception that is not allowed by the previously violated dynamic-exception-specification, andstd::bad_exception()
is not included in that dynamic-exception-specification. ([except.unexpected], paragraph 3) - When the function
std::nested_exception::rethrow_nested()
is called for an object that has captured no exception. ([except.nested], paragraph 4) - When execution of the initial function of a thread exits via an exception. ([thread.thread.constr], paragraph 5)
- See ERR51-CPP. Handle all exceptions for more information.
- When the destructor is invoked on an object of type
std::thread
that refers to a joinable thread. ([thread.thread.destr], paragraph 1) - When the copy assignment operator is invoked on an object of type
std::thread
that refers to a joinable thread. ([thread.thread.assign], paragraph 1) - When calling
condition_variable::wait()
,condition_variable::wait_until()
, orcondition_variable::wait_for()
results in a failure to meet the postcondition:lock.owns_lock() == true
orlock.mutex()
is not locked by the calling thread. ([thread.condition.condvar], paragraphs 11, 16, 21, 28, 33, and 40) - When calling
condition_variable_any::wait()
,condition_variable_any::wait_until()
, orcondition_variable_any::wait_for()
results in a failure to meet the postcondition:lock
is not locked by the calling thread. ([thread.condition.condvarany], paragraphs 11, 16, and 22)
In many circumstances, the call stack will not be unwound in response to an implicit call to std::terminate()
, and in a few cases, it is implementation-defined whether or not stack unwinding will occur. The C++ Standard, [except.terminate], paragraph 2 [ISO/IEC 14882-2014], states, in part:
In the situation where no matching handler is found, it is implementation-defined whether or not the stack is unwound before
std::terminate()
is called. In the situation where the search for a handler encounters the outermost block of a function with a noexcept-specification that does not allow the exception, it is implementation-defined whether the stack is unwound, unwound partially, or not unwound at all beforestd::terminate()
is called. In all other situations, the stack shall not be unwound beforestd::terminate()
is called.
Do not explicitly or implicitly call std::quick_exit()
, std::abort()
, or std::_Exit()
. When the default terminate_handler
is installed or the current terminate_handler
responds by calling std::abort()
or std::_Exit()
, do not explicitly or implicitly call std::terminate()
. Abnormal process termination is the typical vector for denial-of-service attacks.
It is acceptable to call a termination function that safely executes destructors and properly cleans up resources, such as std::exit()
.
Noncompliant Code Example
In this noncompliant code example, the call to f()
, which was registered as an exit handler with std::at_exit()
, may result in a call to std::terminate()
because throwing_func()
may throw an exception:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <cstdlib> void throwing_func() noexcept(false); void f() { // Not invoked by the program except as an exit handler. throwing_func(); } int main() { if (0 != std::atexit(f)) { // Handle error } // ... } |
Compliant Solution
In this compliant solution, f()
handles all exceptions thrown by throwing_func()
and does not rethrow:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <cstdlib> void throwing_func() noexcept(false); void f() { // Not invoked by the program except as an exit handler. try { throwing_func(); } catch (...) { // Handle error } } int main() { if (0 != std::atexit(f)) { // Handle error } // ... } |
Exceptions
ERR50-CPP-EX1: It is acceptable, after indicating the nature of the problem to the operator, to explicitly call std::abort()
, std::_Exit()
, or std::terminate()
in response to a critical program error for which no recovery is possible, as in this example:
Code Block | ||||
---|---|---|---|---|
| ||||
#include <exception> void report(const char *msg) noexcept; [[noreturn]] void fast_fail(const char *msg) { // Report error message to operator report(msg); // Terminate std::terminate(); } void critical_function_that_fails() noexcept(false); void f() { try { critical_function_that_fails(); } catch (...) { fast_fail("Critical function failure"); } } |
Note that the assert()
macro is permissible under this exception because failed assertions will notify the operator on the standard error stream in an implementation-defined manner before calling std::abort()
.
Risk Assessment
Allowing the application to abnormally terminate can lead to resources not being freed, closed, and so on. It is frequently a vector for denial-of-service attacks.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
---|---|---|---|---|---|
ERR50-CPP | Low | Probable | Medium | P4 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
---|---|---|---|---|---|---|---|---|---|
LDRA tool suite |
| 122 S | Enhanced Enforcement | ||||||
| 4037, 4038, 4636, 4637 |
Related Vulnerabilities
Search for other vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
Bibliography
[ISO/IEC 9899-2011] | Subclause 7.20.4.1, "The abort Function"Subclause 7.20.4.4, "The _Exit Function" |
[ISO/IEC 14882-2014] | Subclause 15.5.1, "The |
[MISRA 08] | Rule 15-3-2 (Advisory) Rule 15-3-4 (Required) |