From b76389f22070bb61811eeea41635640d31115fd9 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 7 Jun 2018 18:53:26 -0700 Subject: [PATCH] =?utf8?q?Don=E2=80=99t=20over-align=20if=20WIDE=5FEMACS?= =?utf8?q?=5FINT?= MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit * src/lisp.h (GCALIGNED_UNION): New macro. (struct Lisp_Symbol, union vectorlike_header) (struct Lisp_Cons, struct Lisp_String): Use it to avoid possible over-alignment if !USE_LSB_TAG. --- src/lisp.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/src/lisp.h b/src/lisp.h index c5af4fa6c75..5b296cd04cd 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -229,7 +229,7 @@ extern bool suppress_checking EXTERNALLY_VISIBLE; USE_LSB_TAG not only requires the least 3 bits of pointers returned by malloc to be 0 but also needs to be able to impose a mult-of-8 alignment on some non-GC Lisp_Objects, all of which are aligned via - 'char alignas (GCALIGNMENT) gcaligned;' inside a union. */ + GCALIGNED_UNION at the end of a union. */ enum Lisp_Bits { @@ -277,6 +277,12 @@ DEFINE_GDB_SYMBOL_END (VALMASK) error !; #endif +#if USE_LSB_TAG +# define GCALIGNED_UNION char alignas (GCALIGNMENT) gcaligned; +#else +# define GCALIGNED_UNION +#endif + /* Lisp_Word is a scalar word suitable for holding a tagged pointer or integer. Usually it is a pointer to a deliberately-incomplete type 'union Lisp_X'. However, it is EMACS_INT when Lisp_Objects and @@ -776,7 +782,7 @@ struct Lisp_Symbol /* Next symbol in obarray bucket, if the symbol is interned. */ struct Lisp_Symbol *next; } s; - char alignas (GCALIGNMENT) gcaligned; + GCALIGNED_UNION } u; }; verify (alignof (struct Lisp_Symbol) % GCALIGNMENT == 0); @@ -890,7 +896,7 @@ union vectorlike_header Current layout limits the pseudovectors to 63 PVEC_xxx subtypes, 4095 Lisp_Objects in GC-ed area and 4095 word-sized other slots. */ ptrdiff_t size; - char alignas (GCALIGNMENT) gcaligned; + GCALIGNED_UNION }; verify (alignof (union vectorlike_header) % GCALIGNMENT == 0); @@ -1250,7 +1256,7 @@ struct Lisp_Cons struct Lisp_Cons *chain; } u; } s; - char alignas (GCALIGNMENT) gcaligned; + GCALIGNED_UNION } u; }; verify (alignof (struct Lisp_Cons) % GCALIGNMENT == 0); @@ -1372,7 +1378,7 @@ struct Lisp_String unsigned char *data; } s; struct Lisp_String *next; - char alignas (GCALIGNMENT) gcaligned; + GCALIGNED_UNION } u; }; verify (alignof (struct Lisp_String) % GCALIGNMENT == 0); -- 2.39.5