问题
I'm testing my code on Ubuntu 12.04 with NVIDIA hardware.
No actual OpenCL processing takes place; but my initialization code is still running. This code calls clGetPlatformIDs. However, Valgrind is reporting a memory leak:
==2718== 8 bytes in 1 blocks are definitely lost in loss record 4 of 74
==2718== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2718== by 0x509ECB6: ??? (in /usr/lib/nvidia-current/libOpenCL.so.1.0.0)
==2718== by 0x50A04E1: ??? (in /usr/lib/nvidia-current/libOpenCL.so.1.0.0)
==2718== by 0x509FE9F: clGetPlatformIDs (in /usr/lib/nvidia-current/libOpenCL.so.1.0.0)
I was unaware this was even possible. Can this be fixed? Note that no special deinitialization is currently taking place--do I need to call something after this? The docs don't mention anything about having to deallocate anything.
回答1:
regarding: "Check this out: devgurus.amd.com/thread/136242. valgrind cannot deal with custom memory allocators by design, which OpenCL is likely using"
to quote from the link given: "The behaviour not to free pools at the exit could be called a bug of the library though."
If you want to create a pool of memory and allocate from that, go ahead; but you still should properly deallocate it. The complexity of a memory pool as a whole is no less complex then the complexity of a regular memory reference and deserves at least the same attention, if not more, then that of regular references. Also, an 8 byte structure is highly unlikely to be a memory pool.
Tim Child would have a point about how you use clGetPlatformIds if it was designed to return allocated memory. However, reading http://www.khronos.org/registry/cl/sdk/1.0/docs/man/xhtml/clGetPlatformIDs.html I am not sufficiently convinced this should be the case.
The leak in question may or may not be serious, may or may not accumulate by successive calls, but you might be left only with the option to report the bug to nvidia in hopes they fix it or to find a different opencl implementation for development. Still, there might be reasons for an opencl library to create references to data which from the viewpoint of valgrind are not in use.
Sadly, this still leaves us with a memory leak caused by an external factor we cannot control, and it still leaves us with excess valgrind output.
Say you are sufficiently sure you are not responsible for this leak (say, we know for a fact that an nvidia engineer allocated a random value in OpenCL.so which he didn't deallocate just to spite you). Valgrind has a flag --gen-suppressions=yes, with which you can suppress warnings about particular warnings, which you can feed back to valgrind using --suppressions=$filename. Read the valgrind page for more details about how it works.
Be very wary of using suppressions though. Obviously suppressing errors does not fix them, and liberal usage of the mechanism will lead to situations where you suppress errors made by your code, rather then nvidia or valgrind. Do not suppress warnings of which you are not absolutely sure of where they come from, or regularly reassert your suppressions.
来源：https://stackoverflow.com/questions/15014078/clgetplatformids-memory-leak