DO NOT REPLY [Bug 35121] New: - x86 asm for atomic_cas should use "q" register class

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http://issues.apache.org/bugzilla/show_bug.cgi?id=35121

           Summary: x86 asm for atomic_cas should use "q" register class
           Product: APR
           Version: HEAD
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: APR
        AssignedTo: bugs@httpd.apache.org
        ReportedBy: spam_from_apache_bugzilla@chezphil.org


The inline asm statement implementing apr_atomic_cas for x86 should use the "q"
register class, rather than "r".  "q" specifies a subset of the register set
that is compatible with the instruction used.  With "r" it is possible for the
compiler to select an inappropriate register, subsequently leading to an
assembler error.  Whether it happens seems to depend on gcc version,
optimisation level etc. etc.

See the following mailing list threads for more:

http://gcc.gnu.org/ml/gcc/2005-05/threads.html#01360
http://mail-archives.apache.org/mod_mbox/httpd-dev/200505.mbox/%3c4294665F.2050106@chezphil.org%3e

The affected code was in apr_atomic.h but seems to have moved to atomic.c at
some point.

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