From 011242f927259aa477ebe488a3ee3c4e22081488 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Thu, 10 Nov 2016 20:09:48 +0100 Subject: 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. --- erts/emulator/beam/global.h | 36 +++++++++++++++++++----------------- erts/emulator/beam/utils.c | 6 ++---- 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; } /* -- cgit v1.2.3