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authorSverker Eriksson <[email protected]>2016-11-10 20:09:48 +0100
committerSverker Eriksson <[email protected]>2016-11-17 17:18:10 +0100
commit011242f927259aa477ebe488a3ee3c4e22081488 (patch)
tree2388337f2f326680bf9cb51dcdfc97397c0328f8
parent27e865d01ad49664897662ccc123d825505c0ff6 (diff)
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erts: Tweak PSTACK to avoid warning
warning: array subscript is below array bounds and ok, it's technically undef behavior to set pointer before first array element.
-rw-r--r--erts/emulator/beam/global.h36
-rw-r--r--erts/emulator/beam/utils.c6
2 files changed, 21 insertions, 21 deletions
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 537aaf3177..507ef76e59 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -773,8 +773,8 @@ do { \
typedef struct ErtsPStack_ {
byte* pstart;
- byte* psp;
- byte* pend;
+ int offs; /* "stack pointer" as byte offset from pstart */
+ int size; /* allocated size in bytes */
ErtsAlcType_t alloc_type;
}ErtsPStack;
@@ -785,8 +785,8 @@ void erl_grow_pstack(ErtsPStack* s, void* default_pstack, unsigned need_bytes);
#define PSTACK_DECLARE(s, DEF_PSTACK_SIZE) \
PSTACK_TYPE PSTK_DEF_STACK(s)[DEF_PSTACK_SIZE]; \
ErtsPStack s = { (byte*)PSTK_DEF_STACK(s), /* pstart */ \
- (byte*)(PSTK_DEF_STACK(s) - 1), /* psp */ \
- (byte*)(PSTK_DEF_STACK(s) + (DEF_PSTACK_SIZE)), /* pend */\
+ -(int)sizeof(PSTACK_TYPE), /* offs */ \
+ DEF_PSTACK_SIZE*sizeof(PSTACK_TYPE), /* size */ \
ERTS_ALC_T_ESTACK /* alloc_type */ \
}
@@ -806,19 +806,21 @@ do { \
} \
} while(0)
-#define PSTACK_IS_EMPTY(s) (s.psp < s.pstart)
+#define PSTACK_IS_EMPTY(s) (s.offs < 0)
-#define PSTACK_COUNT(s) (((PSTACK_TYPE*)s.psp + 1) - (PSTACK_TYPE*)s.pstart)
+#define PSTACK_COUNT(s) ((s.offs + sizeof(PSTACK_TYPE)) / sizeof(PSTACK_TYPE))
-#define PSTACK_TOP(s) (ASSERT(!PSTACK_IS_EMPTY(s)), (PSTACK_TYPE*)(s.psp))
+#define PSTACK_TOP(s) (ASSERT(!PSTACK_IS_EMPTY(s)), \
+ (PSTACK_TYPE*)(s.pstart + s.offs))
-#define PSTACK_PUSH(s) \
- (s.psp += sizeof(PSTACK_TYPE), \
- ((s.psp == s.pend) ? erl_grow_pstack(&s, PSTK_DEF_STACK(s), \
- sizeof(PSTACK_TYPE)) : (void)0), \
- ((PSTACK_TYPE*) s.psp))
+#define PSTACK_PUSH(s) \
+ (s.offs += sizeof(PSTACK_TYPE), \
+ ((s.offs == s.size) ? erl_grow_pstack(&s, PSTK_DEF_STACK(s), \
+ sizeof(PSTACK_TYPE)) : (void)0), \
+ ((PSTACK_TYPE*) (s.pstart + s.offs)))
-#define PSTACK_POP(s) ((PSTACK_TYPE*) (s.psp -= sizeof(PSTACK_TYPE)))
+#define PSTACK_POP(s) ((s.offs -= sizeof(PSTACK_TYPE)), \
+ (PSTACK_TYPE*)(s.pstart + s.offs))
/*
* Do not free the stack after this, it may have pointers into what
@@ -831,8 +833,8 @@ do {\
(dst)->pstart = erts_alloc(s.alloc_type,\
sizeof(PSTK_DEF_STACK(s)));\
sys_memcpy((dst)->pstart, s.pstart, _pbytes);\
- (dst)->psp = (dst)->pstart + _pbytes - sizeof(PSTACK_TYPE);\
- (dst)->pend = (dst)->pstart + sizeof(PSTK_DEF_STACK(s));\
+ (dst)->offs = s.offs;\
+ (dst)->size = s.size;\
(dst)->alloc_type = s.alloc_type;\
} else\
*(dst) = s;\
@@ -847,8 +849,8 @@ do { \
ASSERT(s.pstart == (byte*)PSTK_DEF_STACK(s)); \
s = *(src); /* struct copy */ \
(src)->pstart = NULL; \
- ASSERT(s.psp >= (s.pstart - sizeof(PSTACK_TYPE))); \
- ASSERT(s.psp < s.pend); \
+ ASSERT(s.offs >= -(int)sizeof(PSTACK_TYPE)); \
+ ASSERT(s.offs < s.size); \
} while (0)
#define PSTACK_DESTROY_SAVED(pstack)\
diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index cd7131f5df..80c116fdac 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -204,9 +204,8 @@ erl_grow_wstack(ErtsWStack* s, Uint need)
void
erl_grow_pstack(ErtsPStack* s, void* default_pstack, unsigned need_bytes)
{
- Uint old_size = s->pend - s->pstart;
+ Uint old_size = s->size;
Uint new_size;
- Uint sp_offs = s->psp - s->pstart;
if (need_bytes < old_size)
new_size = 2 * old_size;
@@ -220,8 +219,7 @@ erl_grow_pstack(ErtsPStack* s, void* default_pstack, unsigned need_bytes)
sys_memcpy(new_ptr, s->pstart, old_size);
s->pstart = new_ptr;
}
- s->pend = s->pstart + new_size;
- s->psp = s->pstart + sp_offs;
+ s->size = new_size;
}
/*