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girepository: Don't assume a bitfield has a fixed size

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The type used when declaring a bitfield member of a struct doesn't
affect the amount of space allocated for it - only whether it's signed
or unsigned. In standard C99 (6.2.7.1), only _Bool, signed int and
unsigned int or typedefs to them are allowed as bitfield types, but GCC
allows other integer types as an extension.

In this case, the GIBaseInfo and GIBaseInfoStack structs are meant to
have identical layout. However, type_is_embedded was declared as an
unsigned bitfield in the former and a uint32_t in the latter. This was
harmless on most platforms because the following member is an aligned
pointer, but (for example) on m68k-linux-gnu pointers only need to be
16-bit aligned, so GCC only allocates 16 bits for the bitfield.

Change the type in the declaration to unsigned int, and add an padding
bitfield following it to ensure there's space for 32 bits on all
platforms in the future.

Signed-off-by: Adam Sampson <ats@offog.org>
This commit is contained in:
Adam Sampson 2024-05-10 18:37:52 +01:00 committed by Philip Withnall
parent 34626188aa
commit ae33e87117
1 changed files with 2 additions and 1 deletions
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3
girepository/girepository-private.h
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@ -57,7 +57,8 @@ struct _GIBaseInfo
GITypelib *typelib;
uint32_t offset;
uint32_t type_is_embedded : 1; /* Used by GITypeInfo */
unsigned int type_is_embedded : 1; /* Used by GITypeInfo */
unsigned int padding_bitfield : 31; /* For future expansion */
/* A copy of GIBaseInfo is exposed publicly for stack-allocated derivatives
* such as GITypeInfo, so its size is now ABI. */