fastmm4_faq.txt

优化delphi内存编译的组件

Frequently Asked Questions
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Q: When my program shuts down FastMM reports that it has leaked memory. Is it possible that FastMM is wrong?
A: Unfortunately, no. If FastMM reports that a block has been leaked, then it means that a block was allocated but never freed - thus leaked. Use a utility like Memproof to pinpoint the source of the problem.

Q: My program used to work fine with the Borland memory manager, but I get an "Invalid Pointer Operation" or "Access Violation" with FastMM. Is there a bug in FastMM?
A: Highly unlikely. The memory manager is such a critical part of any program and is subjected to such a large amount of traffic that it is rare that a bug of this nature will make it through testing. FastMM works differently than the default memory manager and does more pointer checking, so it will catch more errors. For example: The default MM may allow you to free the same pointer twice while FastMM will immediately raise an "Invalid Pointer Operation" if you try to do so. Compile your application with the "CheckHeapForCorruption" option set in FastMM4.pas - this should raise an error closer to the source of the problem.

Q: My program used to work with replacement memory manager X, but I get an access violation when I try to use FastMM. Why?
A: There may still be a reference to the old memory manager somewhere in the source. Do a "find in files" and check that the old memory manager is not referenced in any "uses" clause. FastMM checks that it is the first memory manager that is being installed, but many other memory managers don't, so it's quite possible that another MM may be installing itself after FastMM.

Q: FastMM doesn't make my program any faster. What's wrong?
A: If your program does not spend much time allocating and freeing memory, then there is little that FastMM can do to speed it up. For example: If your application spends only 1% of its time allocating memory using the default memory manager, a blazingly fast memory manager can at best make it 1% faster. FastMM is much faster than the default MM, but if the bottleneck in your program is not memory management then your gains may not be as great as you had hoped.

Q: I have added FastMM4.pas as the very first unit in my project's .dpr file, but when I try to run my program it still complains that it is not the first unit. Why?
A: If you are using an exception handler that modifies the unit initialization order (like MadExcept), you have to change its configuration so that FastMM is initialized first.

Q: Delphi 2005 crashes with an error message "Class 'TApplication', already if class map" (sic) when I replace the default borlndmm.dll with the FastMM DLL. Why?
A: It is due to a bug in Delphi 2005 (QC#14007). There is an unofficial patch available that fixes this. Refer to FastMM4_Readme.txt for details.

Q: I am using the replacement borlndmm.dll together with the Delphi IDE. When I open up two copies of Delphi and then close one down I get a memory leak report. Why?
A: When compiling the DLL you should set the "NeverUninstall" option.

Q: I am using the replacement borlndmm.dll together with the Delphi 2005 IDE. When I close the IDE it remains in task manager. Why?
A: This is due to a bug (QC#14070). When compiling the DLL you should set the "NeverUninstall" option to work around it.

Q: When a memory error pops up in "FullDebugMode" there is no debug info in the stack traces, only addresses. Why?
A: To be able to get unit/line number info you need to have the "FastMM_DebugInfo.dll" either in the same directory as the application executable or in the path. There must also be debug info available for the application - this can be in the form of a map file, a .jdbg file or embedded jcl debug info.

Q: My program used to work fine, but if I enable "FullDebugMode" and run it I get an access violation at address $8080xxxx. Why?
A: You are attempting to access properties of a freed object. When you free a block in "FullDebugMode", FastMM fills the freed memory area with a pattern of $80 bytes. If there were any pointers, long strings or object references inside the freed object they will now point to $80808080 which is in a reserved address space.

Q: In "FullDebugMode" when an error occurs the stack traces are very incomplete. Why?
A: FastMM can only do a stack trace for routines that set up a stack frame. In the "Project Options" window on the "Compiler" tab, enable the "Stack Frames" option to create stack frames for all procedures.

Q: How do I get my DLL and main application to share FastMM so I can safely pass long strings and dynamic arrays between them?
A: The easiest way is to define ShareMM, ShareMMIfLibrary and AttemptToUseSharedMM in FastMM4.pas and add FastMM4.pas to the top of the uses section of the .dpr for both the main application and the DLL.

Q: I am using Windows x64 edition. How do I enable my applications to address more than 2GB RAM?
A: Add a line containing {$SetPEFlags $20} to the .dpr file. This will set the LARGE_ADDRESS_AWARE flag in the executable and Windows x64 will consequently give the process a full 4GB user address space instead of the usual 2GB.

Q: I get the following error when I try to use FastMM with an application compiled to use packages: "[Error] Need imported data reference ($G) to access 'IsMultiThread' from unit 'FastMM4'". How do I get it to work?
A: Enable the "UseRuntimePackages" option in FastMM4Options.inc.