[Bug c/56341] New: GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341



             Bug #: 56341

           Summary: GCC produces unaligned data access

    Classification: Unclassified

           Product: gcc

           Version: unknown

            Status: UNCONFIRMED

          Severity: major

          Priority: P3

         Component: c

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: bernd.edlin...@hotmail.de





Created attachment 29464

  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29464

test program produces alignment faults



Hello,



The attached test program causes two problems when compiled with GCC 4.6.3 for

ARM:



1. test() fails to write the high word of an unaligned volatile struct member.



2. test1() crashes because it uses an unaligned word access.



This code did compile and execute correctly with GCC 4.3.2



As a workaround, the bug goes away if the code is compiled with

-fno-strict-volatile-bitfields,

but this is probably less efficient code.





The attached patch is a backport of the following patch, and seems to resolve

this issue:



http://gcc.gnu.org/ml/gcc-patches/2012-08/msg01449.html



the original patch ignored the alignment of the target, and fixed only the

first test case, but not the crash in the second test case.



Regards

Bernd Edlinger