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https://issues.apache.org/jira/browse/AVRO-1033?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vivek Nadkarni updated AVRO-1033:
---------------------------------
Attachment: test_refcount.c
AVRO-1033.patch
Attach patch - AVRO-1033.patch.
Attach test program - test_refcount.c.
Note that you have to force the usage of x86 assembly instead of GCC intrinsics
in refcount.h in order to see the memory leak in the test program via valgrind.
You can force this usage by modifying refcount.h or by using an older GCC
compiler (version <= 4.1.0).
> Avro-C reference count fails on x86 and x86-64 for GCC 4.1.0 and earlier
> ------------------------------------------------------------------------
>
> Key: AVRO-1033
> URL: https://issues.apache.org/jira/browse/AVRO-1033
> Project: Avro
> Issue Type: Bug
> Components: c
> Affects Versions: 1.6.2
> Environment: Linux on an x86 or x86-64 platform with GCC version less
> than or equal to 4.1.0.
> Reporter: Vivek Nadkarni
> Fix For: 1.6.3
>
> Attachments: AVRO-1033.patch, test_refcount.c
>
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> Item 1:
> *******
> In the Avro-C implementation, there is a bug in the Raw x86 assembly
> performing the atomic increment and decrement operations in
> refcount.h. Specifically, the assembly language commands (mistakenly)
> operate on the the pointer (refcount) instead of operating on the
> memory pointed to (*refcount). This results in memory leaks, when
> trying to deallocate avro values.
> This problem only occurs when using GCC versions less than 4.1.0. For
> GCC versions greater than 4.1.0, the code uses the GCC intrinsic
> __sync_add_and_fetch() or __sync_sub_and_fetch() instead of the raw
> x86 assembly, and this works properly.
> Since this problem is masked for developers working with new(er) GCC
> compilers, greater than version 4.1.0, one way to "uncover" it is to
> force the GCC intrinsics off by requiring a higher GCC version (say
> 8.1.0) to use the GCC intrinsics. Then GCC falls back to using the x86
> assembly, and the problem can be seen.
> I am attaching a sample test case (test_refcount.c), which will show a
> memory leak when compiled with the raw x86 commands enabled in
> refcount.h and run with valgrind using the following command:
> valgrind -v --leak-check=full --track-origins=yes ./test_refcount
> I am also attaching a simple patch to fix the bug. The patch just
> replaces (refcount) with (*refcount) in a few places, and the memory
> leak disappears.
> Item 2:
> *******
> On a related note, while compiling Avro across several flavors of
> Linux, we noticed that the GCC atomic intrinsics
> __sync_add_and_fetch() and __sync_sub_and_fetch() were not implemented
> for all versions of GCC greater than 4.1.0, causing compile errors.
> Specifically, the following two versions of GCC don't appear to
> support the GCC atomic intrinsics:
> 1. GCC 4.1.2 20080704 (Red Hat 4.1.2-48)
> 2. GCC 4.4.3 on Mandriva for an i586 target
> In our local code we have updated the GCC version test in refcount.h
> to require versions of GCC greater than 4.5.0, before including the
> GCC intrinsics. We might want to do the same in the global Avro
> repository. If appropriate, I can create a separate JIRA item for
> this issue. Please let me know.
> Cheers,
> Vivek Nadkarni
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