ERROR_PAGE_FAULT_COPY_ON_WRITE - 749 (0x2ED)

Technical Meaning

The ERROR_PAGE_FAULT_COPY_ON_WRITE error code indicates that a page fault occurred due to a demand zero fault. This typically happens when the system attempts to access a memory location that is not currently mapped, and it results in a write operation.

Error Details

A page fault occurs when the processor encounters an invalid or unmapped memory address during execution of a program. In this case, the specific type of page fault is a demand zero fault, which means that the system attempted to access a non-existent memory location and expected it to be initialized with zeros.

Usage Context

This error code can occur in various scenarios where the operating system or a user-mode application attempts to write to a memory address that has not been allocated. It is commonly encountered during virtual memory management operations, such as when a process tries to modify a page that is currently shared or mapped read-only.

Developer Interpretation

When encountering this error code, developers should consider the following:

• Memory Management: Ensure that all memory allocations are properly managed and that there are no dangling pointers or invalid references.
• Virtual Memory Operations: Verify that operations involving virtual memory, such as page faults, are handled correctly. This includes ensuring that read-only mappings are not being modified without proper synchronization mechanisms.
• Error Handling: Implement robust error handling to manage situations where a demand zero fault might occur, especially in scenarios where write operations are expected on shared or mapped pages.

Related Errors

• ERROR_INVALID_ADDRESS (487): Occurs when an invalid memory address is accessed.
• STATUS_ACCESS_VIOLATION (c0000005): Indicates a general access violation, which can include page faults.
• STATUS_WRITE_FAULT (c0000012): Occurs during a write operation to an invalid memory location.

FAQ

Q: What does the ERROR_PAGE_FAULT_COPY_ON_WRITE error mean?

A: It indicates that a demand zero fault occurred, meaning the system attempted to access unmapped memory and expected it to be initialized with zeros.

Q: How can I handle this error in my application?

A: Ensure proper memory management and implement robust error handling for virtual memory operations. Use synchronization mechanisms when modifying shared or read-only pages.

Summary

The ERROR_PAGE_FAULT_COPY_ON_WRITE error code is a specific technical indicator of a demand zero fault during page faults. Developers should focus on robust memory management, proper handling of virtual memory operations, and implementing effective error handling strategies to manage such situations.