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https://issues.apache.org/jira/browse/HADOOP-8659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13432054#comment-13432054
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Trevor Robinson commented on HADOOP-8659:
-----------------------------------------
It's not as easy as just CHECK_SYMBOL_EXISTS/CHECK_LIBRARY_EXISTS, since the
soft-float libraries are identical to the hard-float ones, but are installed in
different directories. However, I can do a test compilation against an
arbitrary libc symbol with the soft-float flag:
{code}
include(CMakePushCheckState)
cmake_push_check_state()
set(CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS} -mfloat-abi=softfp)
include(CheckSymbolExists)
check_symbol_exists(exit stdlib.h SOFTFP_AVAILABLE)
cmake_pop_check_state()
{code}
Unfortunately, there is currently no good way to determine the JVM's float ABI.
It's not reported at all by the Oracle EJRE or OpenJDK. The current behavior of
linking against the JVM library with the wrong ABI doesn't report an error.
What I can do is restrict this code path to Linux (since this issue is
Linux-specific for now), where readelf is part of binutils (like ld), so it
should always be available. But I'll also check for it and issue a warning if
it's not found. For example:
{code}
find_program(READELF readelf)
if (READELF MATCHES "NOTFOUND")
message(WARNING "readelf not found; JVM float ABI detection disabled")
endif ()
{code}
> Native libraries must build with soft-float ABI for Oracle JVM on ARM
> ---------------------------------------------------------------------
>
> Key: HADOOP-8659
> URL: https://issues.apache.org/jira/browse/HADOOP-8659
> Project: Hadoop Common
> Issue Type: Bug
> Components: native
> Environment: armhf Linux with Oracle JVM
> Reporter: Trevor Robinson
> Assignee: Trevor Robinson
> Attachments: HADOOP-8659.patch, HADOOP-8659.patch, HADOOP-8659.patch
>
>
> There was recently an ABI (application binary interface) change in most Linux
> distributions for modern ARM processors (ARMv7). Historically, hardware
> floating-point (FP) support was optional/vendor-specific for ARM processors,
> so for software compatibility, the default ABI required that processors with
> FP units copy FP arguments into integer registers (or memory) when calling a
> shared library function. Now that hardware floating-point has been
> standardized for some time, Linux distributions such as Ubuntu 12.04 have
> changed the default ABI to leave FP arguments in FP registers, since this can
> significantly improve performance for FP libraries.
> Unfortunately, Oracle has not yet released a JVM (as of 7u4) that supports
> the new ABI, presumably since this involves some non-trivial changes to
> components like JNI. While the soft-float JVM can run on systems with
> multi-arch support (currently Debian/Ubuntu) using compatibility libraries,
> this configuration requires that any third-party JNI libraries also be
> compiled using the soft-float ABI. Since hard-float systems default to
> compiling for hard-float, an extra argument to GCC (and installation of a
> compatibility library) is required to build soft-float Hadoop native
> libraries that work with the Oracle JVM.
> Note that OpenJDK on hard-float systems does use the new ABI, and expects JNI
> libraries to use it as well. Therefore the fix for this issue requires
> detecting the float ABI of the current JVM.
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