Do not use packed structures in soft-fp

System Internals / glibc - Joseph Myers [] - 1 February 2018 20:44 EST

Building for soft-float ColdFire produces an error in soft-fp:

In file included from ../sysdeps/ieee754/soft-fp/s_fmaf.c:42: ../soft-fp/single.h:85:3: error: 'packed' attribute ignored for field of type 'struct ' [-Werror=attributes] } bits __attribute__ ((packed)); ^

While this error only appears in that particular case, this attribute is in fact never useful, on any architecture. If you have

struct __attribute__ ((packed)) { ... } bits;


struct { ... } __attribute__ ((packed)) bits;

then the attribute affects the layout of the structure type. But with the form used in this code

struct { ... } bits __attribute__ ((packed));

the field bits is being declared packed, but the layout of its type has already been determined at that point. If on any platform the layout of the sequence of bit-fields were wrong without the use of a packed attribute, the attribute would need to be used via a definition of _FP_STRUCT_LAYOUT, not in its present position.

So this patch removes the useless attribute to fix the build for ColdFire soft-float. Tested with that installed stripped shared libraries are unchanged by the patch.

- soft-fp/double.h (union _FP_UNION_D): Do not use attribute packed on bits.
- soft-fp/extended.h (union _FP_UNION_E): Likewise.
- soft-fp/half.h (union _FP_UNION_H): Likewise.
- soft-fp/quad.h (union _FP_UNION_Q): Likewise.
- soft-fp/single.h (union _FP_UNION_S): Likewise.

049375e2b5 Do not use packed structures in soft-fp.
ChangeLog | 9 +++++++++
soft-fp/double.h | 4 ++--
soft-fp/extended.h | 2 +-
soft-fp/half.h | 2 +-
soft-fp/quad.h | 2 +-
soft-fp/single.h | 2 +-
6 files changed, 15 insertions(+), 6 deletions(-)


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