From e37eb0fc1f63460f2b38ba6308be4c6099f06f48 Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Sun, 31 May 2009 21:46:14 +0200 Subject: [PATCH] Improve comments. --- ChangeLog | 6 ++++++ lib/alignof.h | 11 ++++++++--- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/ChangeLog b/ChangeLog index a8367d4647..54172a3942 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2009-05-31 Bruno Haible + + * lib/alignof.h (alignof_slot, alignof_type, alignof): Document + restriction due to compiler bugs. + Reported by Eric Blake. + 2009-05-31 Simon Josefsson Bruno Haible diff --git a/lib/alignof.h b/lib/alignof.h index b09d0078ea..bc52cb33ff 100644 --- a/lib/alignof.h +++ b/lib/alignof.h @@ -21,7 +21,9 @@ #include /* Determine the alignment of a structure slot (field) of a given type, - at compile time. Note that the result depends on the ABI. */ + at compile time. Note that the result depends on the ABI. + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ #if defined __cplusplus template struct alignof_helper { char __slot1; type __slot2; }; # define alignof_slot(type) offsetof (alignof_helper, __slot2) @@ -33,7 +35,9 @@ Note that this is not necessarily the same as alignof_slot(type). For example, with GNU C on x86 platforms: alignof_type(double) = 8, but - when -malign-double is not specified: alignof_slot(double) = 4, - - when -malign-double is specified: alignof_slot(double) = 8. */ + - when -malign-double is specified: alignof_slot(double) = 8. + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ #if defined __GNUC__ # define alignof_type __alignof__ #else @@ -42,7 +46,8 @@ /* alignof is an alias for alignof_slot semantics, since that's what most callers need. - Note: The result cannot be used as a value for an 'enum' constant, */ + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ #define alignof alignof_slot #endif /* _ALIGNOF_H */ -- 2.30.2