VirtualFree Perform (Memoryapi.h)
Releases, decommits, or releases and decommits a region of pages within the digital tackle space of the calling process. To free memory allocated in another process by the VirtualAllocEx operate, use the VirtualFreeEx operate. A pointer to the base handle of the area of pages to be freed. Launch, this parameter should be the bottom deal with returned by the VirtualAlloc function when the region of pages is reserved. The size of the region of memory to be freed, in bytes. Release, this parameter must be zero (zero). The operate frees all the region that's reserved in the initial allocation name to VirtualAlloc. Measurement). This means, for instance, that a 2-byte region of Memory Wave Method that straddles a web page boundary causes each pages to be decommitted. If lpAddress is the bottom tackle returned by VirtualAlloc and dwSize is 0 (zero), the function decommits the whole region that's allocated by VirtualAlloc.
After that, the complete region is within the reserved state. The type of free operation. This parameter must be one in every of the next values. The function doesn't fail when you try to decommit an uncommitted page. This implies that you would be able to decommit a spread of pages without first determining the present commitment state. DECOMMIT worth isn't supported when the lpAddress parameter offers the bottom handle for an enclave. That is true for enclaves that don't assist dynamic memory administration (i.e. SGX1). DECOMMIT anyplace within the enclave. When you specify this worth, dwSize should be zero (zero), and lpAddress must level to the bottom handle returned by the VirtualAlloc perform when the area is reserved. The perform fails if either of these situations just isn't met. If any pages in the region are committed at the moment, the function first decommits, and then releases them. The perform does not fail when you try to launch pages that are in different states, some reserved and some committed.
This implies which you could release a variety of pages with out first determining the present commitment state. Launch, this parameter can moreover specify certainly one of the following values. If the operate succeeds, the return value is nonzero. If the function fails, the return value is 0 (zero). To get extended error info, Memory Wave Method name GetLastError. Every page of memory in a process virtual address space has a Web page State. The VirtualFree operate can decommit a range of pages which might be in numerous states, some committed and some uncommitted. This means which you could decommit a range of pages without first figuring out the present dedication state of each web page. Decommitting a web page releases its physical storage, either in memory or within the paging file on disk. If a web page is decommitted however not launched, its state adjustments to reserved. Subsequently, you may name VirtualAlloc to commit it, or VirtualFree to launch it. Makes an attempt to learn from or write to a reserved web page leads to an entry violation exception.
The VirtualFree operate can launch a variety of pages that are in different states, some reserved and a few committed. This implies you could release a variety of pages without first figuring out the present commitment state of each web page. All the range of pages initially reserved by the VirtualAlloc operate must be launched at the identical time. If a page is launched, its state adjustments to free, and it is on the market for subsequent allocation operations. After memory is launched or decommited, you can by no means check with the memory once more. Any data which will have been in that memory is gone forever. Attempting to learn from or write to a free page results in an entry violation exception. Should you want to maintain info, don't decommit or free memory that accommodates the knowledge. The VirtualFree operate can be used on an AWE area of memory, and it invalidates any physical web page mappings within the area when freeing the tackle area. Nonetheless, the physical web page just isn't deleted, and the appliance can use them. The application must explicitly call FreeUserPhysicalPages to free the bodily pages. When the method is terminated, all sources are cleaned up routinely. Windows 10, version 1709 and later and Windows 11: To delete the enclave when you finish utilizing it, call DeleteEnclave. You can not delete a VBS enclave by calling the VirtualFree or VirtualFreeEx operate. You possibly can still delete an SGX enclave by calling VirtualFree or VirtualFreeEx. The base tackle of the enclave for the lpAddress parameter. Zero for the dwSize parameter. Release for the dwFreeType parameter.