[ wxwindows-Bugs-1844128 ] undefined reference to `__sync_sub_and_fetch_4'

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Bugs item #1844128, was opened at 2007-12-04 16:05
Message generated for change (Settings changed) made by vaclavslavik
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Category: Build -- unix
Group: Platform specific
>Status: Closed
Resolution: Fixed
Priority: 5
Private: No
Submitted By: Andrew Ziem (andrewziem)
Assigned to: Vaclav Slavik (vaclavslavik)
Summary: undefined reference to `__sync_sub_and_fetch_4'

Initial Comment:
Building 2007-12-04 SVN on Fedora 7 i686 with GCC 4.1.2, I get a build error in the tests directory:




g++ -o test test_test.o test_archivetest.o test_ziptest.o test_tartest.o test_arrays.o test_base64.o test_fileconf.o test_datetimetest.o test_filekind.o test_filenametest.o test_filesystest.o test_fontmaptest.o test_formatconvertertest.o test_hashes.o test_intltest.o test_lists.o test_longlongtest.o test_convautotest.o test_mbconvtest.o test_regextest.o test_wxregextest.o test_scopeguardtest.o test_iostream.o test_strings.o test_stdstrings.o test_tokenizer.o test_unichar.o test_unicode.o test_vararg.o test_crt.o test_vsnprintf.o test_bstream.o test_datastreamtest.o test_ffilestream.o test_fileback.o test_filestream.o test_largefile.o test_memstream.o test_sstream.o test_tempfile.o test_textstreamtest.o test_zlibstream.o test_textfiletest.o test_atomic.o test_queue.o test_uris.o test_vectors.o -pthread     -L/home/z/tmp/wxWidgets/lib  -Wl,-rpath,/home/z/tmp/wxWidgets/lib -lcppunit -ldl  -lz -ldl -lm -lwx_baseu_net-2.9  -lwx_baseu-2.9    -lwxregexu-2.9 -lwxexpat-2.9 -pthread  -Wl,--version-script,/home/z/tmp/wxWidgets/version-script -lz -ldl -lm 
test_atomic.o: In function `AtomicTestCase::MyThread::Entry()':
atomic.cpp:(.text+0x51): undefined reference to `__sync_sub_and_fetch_4'
atomic.cpp:(.text+0x9f): undefined reference to `__sync_sub_and_fetch_4'
test_atomic.o: In function `AtomicTestCase::TestNoThread()':
atomic.cpp:(.text+0xad5): undefined reference to `__sync_sub_and_fetch_4'
test_atomic.o: In function `AtomicTestCase::TestDecReturn()':
atomic.cpp:(.text+0x170e): undefined reference to `__sync_sub_and_fetch_4'
atomic.cpp:(.text+0x187d): undefined reference to `__sync_sub_and_fetch_4'
collect2: ld returned 1 exit status


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Comment By: Vaclav Slavik (vaclavslavik)
Date: 2007-12-05 12:03

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*Really* fixed now. Apparently, this is gcc's normal behavior if the
required primitives aren't supported by the architecture (as is the case
with i686, unlike x86_64):

    Not all operations are supported by all target processors.  If a
   particular operation cannot be implemented on the target processor, a
   warning will be generated and a call an external function will be
   generated.  The external function will carry the same name as the
   builtin, with an additional suffix `_N' where N is the size of the
data
   type.

Our configure test didn't fail, because it didn't use __sync_sub_and_fetch
return value -- and because int32_t memory access is always atomic on i686,
the compiler correctly determined this use is supported by target
architecture -- but wx uses the return value and that's not supported.

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Comment By: Andrew Ziem (andrewziem)
Date: 2007-12-05 04:29

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Sorry, I still get the same error.  To be sure, I "rm -rf wxWidgets",
retrieved code from SVN trunk, and "./configure --enable debug;make".

Please note I do have __sync_sub_and_fetch but not __sync_sub_and_fetch_4.
 I am not sure where _4 comes from.  Is it the difference between int and
wxUint32?

I will attach config.log if that helps.
File Added: config.log

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Comment By: Vaclav Slavik (vaclavslavik)
Date: 2007-12-04 16:30

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Interesting... This is gcc's builtin function and 4.1.2 certainly does
have it. Could it be a bug in GCC related to compiler flags (see
http://www.usenetarticles.com/thread/953850.html)?

I changed configure test to try linking the app too, so it should
correctly detect that the builtins don't work on your system, but that
means that an inefficient version of this code will be used, it would be
nice to understand what's wrong...

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