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author | Paul Eggert <eggert@cs.ucla.edu> | 2019-04-25 13:42:50 -0700 |
---|---|---|
committer | Paul Eggert <eggert@cs.ucla.edu> | 2019-04-25 13:47:27 -0700 |
commit | 83b0fc30d4bd6799e9593685d1767dfe2b3648a7 (patch) | |
tree | 42b26f45f611a938e6f917ce1de167d9ef534d72 | |
parent | 69947311d84a2572e8382e401ab97fdab25cb433 (diff) | |
download | emacs-83b0fc30d4bd6799e9593685d1767dfe2b3648a7.tar.gz |
Minor tweaks to recent UBSan-related fix
* src/alloc.c: No need to include stdalign.h; it’s pervasive.
(GC_STRING_OVERRUN_COOKIE_SIZE): Align to sdata’s alignment,
so that the code works even if alignof (sdata) exceeds 8.
Don’t require the cookie size to be 8, as this overly fattens
32-bit platforms and one DEADBEEF should be enough.
(GC_STRING_EXTRA): Omit now-unnecessary ‘verify’.
(allocate_string_data): Omit unnecessary cast.
-rw-r--r-- | src/alloc.c | 20 |
1 files changed, 6 insertions, 14 deletions
diff --git a/src/alloc.c b/src/alloc.c index 3b5e3bb9b01..c4ef4e96863 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -21,7 +21,6 @@ along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */ #include <config.h> #include <errno.h> -#include <stdalign.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> @@ -1576,16 +1575,15 @@ static struct Lisp_String *string_free_list; #ifdef GC_CHECK_STRING_OVERRUN -/* We check for overrun in string data blocks by appending a small +/* Check for overrun in string data blocks by appending a small "cookie" after each allocated string data block, and check for the presence of this cookie during GC. */ - -#define GC_STRING_OVERRUN_COOKIE_SIZE 8 +# define GC_STRING_OVERRUN_COOKIE_SIZE ROUNDUP (4, alignof (sdata)) static char const string_overrun_cookie[GC_STRING_OVERRUN_COOKIE_SIZE] = - { '\xde', '\xad', '\xbe', '\xef', '\xde', '\xad', '\xbe', '\xef' }; + { '\xde', '\xad', '\xbe', '\xef', /* Perhaps some zeros here. */ }; #else -#define GC_STRING_OVERRUN_COOKIE_SIZE 0 +# define GC_STRING_OVERRUN_COOKIE_SIZE 0 #endif /* Value is the size of an sdata structure large enough to hold NBYTES @@ -1615,13 +1613,7 @@ static char const string_overrun_cookie[GC_STRING_OVERRUN_COOKIE_SIZE] = #endif /* not GC_CHECK_STRING_BYTES */ /* Extra bytes to allocate for each string. */ - -#define GC_STRING_EXTRA (GC_STRING_OVERRUN_COOKIE_SIZE) - -/* Make sure that allocating the extra bytes doesn't misalign - `sdata'. */ - -verify (GC_STRING_EXTRA % alignof (sdata) == 0); +#define GC_STRING_EXTRA GC_STRING_OVERRUN_COOKIE_SIZE /* Exact bound on the number of bytes in a string, not counting the terminating NUL. A string cannot contain more bytes than @@ -1882,7 +1874,7 @@ allocate_string_data (struct Lisp_String *s, data->string = s; b->next_free = (sdata *) ((char *) data + needed + GC_STRING_EXTRA); - eassert ((uintptr_t) (char *) b->next_free % alignof (sdata) == 0); + eassert ((uintptr_t) b->next_free % alignof (sdata) == 0); MALLOC_UNBLOCK_INPUT; |