------- Comment #4 from ebotcazou at gcc dot gnu dot org 2009-07-04 13:52 ------- > If "-mno-faster-structs" is the default, then surely it shouldn't be > generating ldd/std in this case (and assuming the 8-byte alignment for > "union myblock").
No, -mno-faster-structs doesn't modify the ABI. The SPARC ABI requires union myblock to have 64-bit alignment because it contains a structure that has 64-bit alignment because it contains a double. So the compiler can always use ldd for union myblock. -mfaster-structs does modify the ABI by promoting structures that have less than 64-bit alignment as per the SPARC ABI, e.g. struct b_two. Without it, ldd cannot be used for struct b_two; with it, lld can be used for struct b_two. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40645
