Sunday, March 13, 2011

fwd: heap memory allocation - java/c#/C

Thanks Nigel or the article. A quick glance suggests to me the allocation (not the de-allocation) procedure is no different from malloc, logically.


At run time, the memory management library (some functions pre-loaded into the code section of the address space) gives out small chunks of memory to the requesting application. When there's insufficient "small chunks" to satisfy a request[1], the library synchronously grabs a large block from OS, and adds this large block to the private free-store, which is private to the process, managed by the library. This is the malloc() behavior I know.

[1] perhaps due to fragmentation

This "library" is compiled binary code. For c/c++, I think this means platform-specific object code. For java, this means platform-independent java bytecode, or more likely platform-specific native code.

For dotnet, I guess it's windows native binary code. Now, is this binary code compiled from a C linker/compiler that used the standard malloc() function? I think it's possible. If the dotnet runtime is itself written in C, then the runtime (including the  memory library) is compiled/linked with a C compiler/linker. It's therefore possible to use the malloc library.

Alternatively, I guess it's also possible to create a custom memory module with an equivalent function to malloc(). I make this claim because Microsoft created its own version of C compiler and C memory management library since the early days of C.

Subject: RE: question on heap memory allocation


Does this use malloc ?

Subject: question on heap memory allocation

Hi Nigel,

Someone speculated that "in any programming language, heap memory is allocated always using the C function malloc(). There's no alternative." I know JVM and dotnet runtime are both written in C/c++ so at run time, heap memory is grabbed from OS probably by malloc(). Not sure about other languages.

Is my understanding correct?

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