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comparison src/alloc.c @ 369:1d62742628b6 r21-1-14

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Import from CVS: tag r21-1-14
author cvs
date Mon, 13 Aug 2007 11:01:51 +0200
parents 7347b34c275b
children cc15677e0335
comparison
equal deleted inserted replaced
368:397a7324211a 369:1d62742628b6
1020 1020
1021 Even if Emacs is run on some weirdo system that allows and allocates 1021 Even if Emacs is run on some weirdo system that allows and allocates
1022 byte-aligned pointers, this pointer is at the very top of the address 1022 byte-aligned pointers, this pointer is at the very top of the address
1023 space and so it's almost inconceivable that it could ever be valid. */ 1023 space and so it's almost inconceivable that it could ever be valid. */
1024 1024
1025 #if INTBITS == 32 1025 #if SIZEOF_LONG == 4
1026 # define INVALID_POINTER_VALUE 0xFFFFFFFF 1026 # define INVALID_POINTER_VALUE 0xFFFFFFFFUL
1027 #elif INTBITS == 48 1027 #elif SIZEOF_LONG == 8
1028 # define INVALID_POINTER_VALUE 0xFFFFFFFFFFFF 1028 # define INVALID_POINTER_VALUE 0xFFFFFFFFFFFFFFFFUL
1029 #elif INTBITS == 64
1030 # define INVALID_POINTER_VALUE 0xFFFFFFFFFFFFFFFF
1031 #else 1029 #else
1032 You have some weird system and need to supply a reasonable value here. 1030 You have some weird system and need to supply a reasonable value here.
1033 #endif 1031 #endif
1034 1032
1033 /* The construct (* (void **) (ptr)) would cause aliasing problems
1034 with modern optimizing compilers like `gcc -O3 -fstrict-aliasing'.
1035 But `char *' can legally alias any pointer. Hence this union trick...
1036
1037 It turned out that the union trick was not good enough for xlC -O3;
1038 and it is questionable whether it really complies with the C standard.
1039 so we use memset instead, which should be safe from optimizations. */
1040 typedef union { char c; void *p; } *aliasing_voidpp;
1041 #define ALIASING_VOIDPP_DEREFERENCE(ptr) \
1042 (((aliasing_voidpp) (ptr))->p)
1035 #define FREE_STRUCT_P(ptr) \ 1043 #define FREE_STRUCT_P(ptr) \
1036 (* (void **) ptr == (void *) INVALID_POINTER_VALUE) 1044 (ALIASING_VOIDPP_DEREFERENCE (ptr) == (void *) INVALID_POINTER_VALUE)
1037 #define MARK_STRUCT_AS_FREE(ptr) \ 1045 #define MARK_STRUCT_AS_FREE(ptr) memset (ptr, 0xff, sizeof (void *))
1038 (* (void **) ptr = (void *) INVALID_POINTER_VALUE) 1046 #define MARK_STRUCT_AS_NOT_FREE(ptr) memset (ptr, 0x00, sizeof (void *))
1039 #define MARK_STRUCT_AS_NOT_FREE(ptr) \
1040 (* (void **) ptr = 0)
1041 1047
1042 #ifdef ERROR_CHECK_GC 1048 #ifdef ERROR_CHECK_GC
1043 1049
1044 #define PUT_FIXED_TYPE_ON_FREE_LIST(type, structtype, ptr) \ 1050 #define PUT_FIXED_TYPE_ON_FREE_LIST(type, structtype, ptr) \
1045 do { if (type##_free_list_tail) \ 1051 do { if (type##_free_list_tail) \