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b1573a97e1
Use alignas and unions to specify alignments of objects needing
addresses that are at least a multiple of GCALIGNMENT. Using
these standard C facilities should be safer than relying on ad hoc
and poorly-understood features like GCC’s __attribute__
((aligned (N))), the root cause for recent porting bugs like
Bug#29040. The alignas macro was standardized by C11 and Gnulib
supports alignas for pre-C11 platforms. I have tested this on Sun
Studio 12 sparc (2007) and GCC 4.4.7 x86-64 (2012) as well as on
more recent platforms like GCC 7.2.1 (2017) on Fedora 26 (both
x86-64 and x86).
* lib-src/make-docfile.c (close_emacs_globals): lispsym is now
just an array of struct Lisp_Symbol, since struct Lisp_Symbol is
now properly aligned. All uses changed.
* src/alloc.c (NEXT_FREE_LISP_STRING): Just use the new u.next
member; this is simpler and safer than casting a pointer that
might not be aligned properly.
(aligned_Lisp_Symbol): Remove. No longer needed, now that struct
Lisp_Symbol is aligned properly. All uses replaced with struct
Lisp_Symbol.
* src/lisp.h (GCALIGNED): Remove, as it does not work as expected:
it can cause the natural alignment to be ignored. All uses
replaced by unions with a ‘char alignas (GCALIGNMENT)’ member as
described below.
(struct Lisp_Symbol, struct Lisp_Cons, struct Lisp_String):
Change definition from ‘struct TAG { MEMBERS };’ to
‘struct TAG { union { struct { MEMBERS } s; char alignas
(GCALIGNMENT) gcaligned; } u; };’. This guarantees ‘struct TAG’
to have an alignment that at least max (GCALIGNMENT, N) where N is
its old alignment. All uses like ‘PTR->MEMBER’ changed to
‘PTR->u.s.MEMBER’; these uses were supposed to be mostly private
anyway. Verify that the resulting ‘struct TAG’ is properly
aligned for Emacs.
(union vectorlike_header): New member ‘gcaligned’ to guarantee
that this type, and its containing types like ‘struct Lisp_Subr’,
‘struct buffer’ and ‘struct thread_state’, are all properly
aligned for Emacs.
(struct Lisp_String): New union member ‘next’, for the benefit
of NEXT_FREE_LISP_STRING.
(union Aligned_Cons, union Aligned_String): Remove. All uses
replaced by struct Lisp_Cons and struct Lisp_String, since they
are now properly aligned.
(USE_STACK_CONS, USE_STACK_STRING): Simplify now that we can
assume struct Lisp_Cons and struct Lisp_String are properly
aligned.
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| .. | ||
| ChangeLog.1 | ||
| COPYING | ||
| ctags.c | ||
| ebrowse.c | ||
| emacsclient.c | ||
| etags.c | ||
| hexl.c | ||
| make-docfile.c | ||
| Makefile.in | ||
| movemail.c | ||
| ntlib.c | ||
| ntlib.h | ||
| pop.c | ||
| pop.h | ||
| profile.c | ||
| rcs2log | ||
| README | ||
| update-game-score.c | ||
This directory contains the source code for the architecture-dependent
files that go in ${archlibdir}. At present, these are mostly utility
programs used by GNU Emacs.