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Difference between revisions of "cpp/error/rethrow exception"

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{{cpp/title|rethrow_exception}}
 
{{cpp/title|rethrow_exception}}
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{{ddcl|header=exception|since=c++11|
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{{ddcl | header=exception | notes={{mark since c++11}} |
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[[noreturn]] void rethrow_exception( std::exception_ptr p );
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[[noreturn]] void rethrow_exception( std::exception_ptr p )
+
 
}}
 
}}
  
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Throws the previously captured exception object, referred to by the exception pointer {{tt|p}}.
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Throws the previously captured exception object referred-to by the exception pointer {{c|p}}, or a copy of that object.
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It is unspecified whether a copy is made. If a copy is made, the storage for it is allocated in an unspecified way.
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The behavior is undefined if {{c|p}} is null.
  
 
===Parameters===
 
===Parameters===
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{{param list begin}}
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{{par begin}}
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{{param list item | p | non-null {{cpp|std::exception_ptr}} }}
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{{par|p|non-null {{lc|std::exception_ptr}}}}
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{{par end}}
  
 
===Return value===
 
===Return value===
−
 
 
(none)
 
(none)
  
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{{cpp/error/exception/exception_ptr_example}}
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===Exceptions===
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The exception object referred-to by {{c|p}} if no copy is made.
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Otherwise, a copy of such exception object if the implementation successfully copied the exception object.
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Otherwise, {{lc|std::bad_alloc}} or the exception thrown when copying the exception object, if allocation or copying fails, respectively.
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===Notes===
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Before {{wg21|P1675R2}}, {{tt|rethrow_exception}} was not allowed to copy the exception object, which is unimplementable on some platforms where exception objects are allocated on the stack.
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===Example===
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{{include|cpp/error/example_exception_ptr}}
  
 
===See also===
 
===See also===
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{{dcl list template | cpp/error/exception/dcl list exception_ptr}}
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{{dsc inc|cpp/error/dsc exception_ptr}}
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{{dcl list template | cpp/error/exception/dcl list current_exception}}
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{{dsc inc|cpp/error/dsc current_exception}}
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 09:48, 9 July 2024

 
C++
 
Diagnostics library
 
Defined in header <exception>
[[noreturn]] void rethrow_exception( std::exception_ptr p );
 (since C++11)

Throws the previously captured exception object referred-to by the exception pointer p, or a copy of that object.

It is unspecified whether a copy is made. If a copy is made, the storage for it is allocated in an unspecified way.

The behavior is undefined if p is null.

Contents

[edit] Parameters

p - non-null std::exception_ptr

[edit] Return value

(none)

[edit] Exceptions

The exception object referred-to by p if no copy is made.

Otherwise, a copy of such exception object if the implementation successfully copied the exception object.

Otherwise, std::bad_alloc or the exception thrown when copying the exception object, if allocation or copying fails, respectively.

[edit] Notes

Before P1675R2, rethrow_exception was not allowed to copy the exception object, which is unimplementable on some platforms where exception objects are allocated on the stack.

[edit] Example

[edit]
Run this code
#include <exception>
#include <iostream>
#include <stdexcept>
#include <string>
 
void handle_eptr(std::exception_ptr eptr) // passing by value is OK
{
    try
    {
        if (eptr)
            std::rethrow_exception(eptr);
    }
    catch(const std::exception& e)
    {
        std::cout << "Caught exception: '" << e.what() << "'\n";
    }
}
 
int main()
{
    std::exception_ptr eptr;
 
    try
    {
        [[maybe_unused]]
        char ch = std::string().at(1); // this generates a std::out_of_range
    }
    catch(...)
    {
        eptr = std::current_exception(); // capture
    }
 
    handle_eptr(eptr);
 
} // destructor for std::out_of_range called here, when the eptr is destructed

Possible output: 

Caught exception: 'basic_string::at: __n (which is 1) >= this->size() (which is 0)'

[edit] See also

(C++11)
 shared pointer type for handling exception objects
(typedef) [edit]
(C++11)
 captures the current exception in a std::exception_ptr
(function) [edit]
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