Hi Jeffrey! On Tue, 2023-11-14 at 00:50 -0500, Jeffrey Walton wrote: > On SPARC, 64-bit words can be loaded and saved through one of two > instructions. The first version is optimized, the second version is > not. The optimized version is faster, but the 64-bit words have to be > aligned to 8-byte boundaries. I.e., naturally aligned. > > If you are performing unaligned loads of 64-bit words, then you have > to specify the compiler option -xmemalign=4i. -xmemalign=4i will > generate the inefficient load, but it will avoid the SIGBUS. > > When using the default toolchain settings, -xmemalign=8s is used, > which causes the toolchain to use the optimized loads. I think that is > what is generating the UBsan finding "runtime error: member access > within misaligned address ... which requires 8 byte alignment." > > Also see "3.4.151 –xmemalign[=<a><b>]", > <https://docs.oracle.com/cd/E37069_01/html/E37076/aevkc.html>, in the > Solaris manual. > > > [1] > > https://www.gnu.org/software/libc/manual/html_node/Obstacks-Data-Alignment.html
This is completely new to me and really interesting, thanks for the heads-up! However, I think this particular flag is not available in GCC or LLVM, is it? Thanks, Adrian -- .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
