diff options
Diffstat (limited to 'generic/tclInt.h')
| -rw-r--r-- | generic/tclInt.h | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/generic/tclInt.h b/generic/tclInt.h index 527572e..445dc8a 100644 --- a/generic/tclInt.h +++ b/generic/tclInt.h @@ -2314,22 +2314,34 @@ typedef struct Interp { #endif /* - * This macro is used to determine the offset needed to safely allocate any + * TCL_ALIGN is used to determine the offset needed to safely allocate any * data structure in memory. Given a starting offset or size, it "rounds up" - * or "aligns" the offset to the next 8-byte boundary so that any data - * structure can be placed at the resulting offset without fear of an - * alignment error. + * or "aligns" the offset to the next aligned (typically 8-byte) boundary so + * that any data structure can be placed at the resulting offset without fear + * of an alignment error. Note this is clamped to a minimum of 8 for API + * compatibility. * * WARNING!! DO NOT USE THIS MACRO TO ALIGN POINTERS: it will produce the - * wrong result on platforms that allocate addresses that are divisible by 4 - * or 2. Only use it for offsets or sizes. + * wrong result on platforms that allocate addresses that are divisible by a + * non-trivial factor of this alignment. Only use it for offsets or sizes. * * This macro is only used by tclCompile.c in the core (Bug 926445). It * however not be made file static, as extensions that touch bytecodes * (notably tbcload) require it. */ -#define TCL_ALIGN(x) (((int)(x) + 7) & ~7) +struct TclMaxAlignment { + char unalign[8]; + union { + long long maxAlignLongLong; + double maxAlignDouble; + void *maxAlignPointer; + } aligned; +}; +#define TCL_ALIGN_BYTES \ + offsetof(struct TclMaxAlignment, aligned) +#define TCL_ALIGN(x) \ + (((x) + (TCL_ALIGN_BYTES - 1)) & ~(TCL_ALIGN_BYTES - 1)) /* * A common panic alert when memory allocation fails. |