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fix race in which some instruction name symbols could go unmarked

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* libguile/instructions.c: In loops, replace scm_op_last with
  SCM_VM_NUM_INSTRUCTIONS.
  (fetch_instruction_table): Protect the instruction symbols from
  collection. Before they were only marked by the name->opcode hash
  table, leading to races in which they could be collected.
  (scm_lookup_instruction_by_name): Protect the hash table earlier, as
  it's not actually a stack variable, since it's static.
This commit is contained in:
Andy Wingo 2009-07-02 17:46:23 +02:00
parent cec1d4e33f
commit ad47e35939
2 changed files with 9 additions and 9 deletions
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17
libguile/instructions.c
View file

@ -53,7 +53,7 @@ fetch_instruction_table ()
if (SCM_UNLIKELY (!table))
{
size_t bytes = scm_op_last * sizeof(struct scm_instruction);
size_t bytes = SCM_VM_NUM_INSTRUCTIONS * sizeof(struct scm_instruction);
int i;
table = malloc (bytes);
memset (table, 0, bytes);
@ -63,11 +63,12 @@ fetch_instruction_table ()
#include <libguile/vm-i-scheme.i>
#include <libguile/vm-i-loader.i>
#undef VM_INSTRUCTION_TO_TABLE
for (i = 0; i < scm_op_last; i++)
for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
{
table[i].opcode = i;
if (table[i].name)
table[i].symname = scm_from_locale_symbol (table[i].name);
table[i].symname =
scm_permanent_object (scm_from_locale_symbol (table[i].name));
else
table[i].symname = SCM_BOOL_F;
}
@ -85,12 +86,12 @@ scm_lookup_instruction_by_name (SCM name)
if (SCM_UNLIKELY (SCM_FALSEP (instructions_by_name)))
{
int i;
instructions_by_name = scm_make_hash_table (SCM_I_MAKINUM (scm_op_last));
for (i = 0; i < scm_op_last; i++)
instructions_by_name = scm_permanent_object
(scm_make_hash_table (SCM_I_MAKINUM (SCM_VM_NUM_INSTRUCTIONS)));
for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
if (scm_is_true (table[i].symname))
scm_hashq_set_x (instructions_by_name, table[i].symname,
SCM_I_MAKINUM (i));
instructions_by_name = scm_permanent_object (instructions_by_name);
}
op = scm_hashq_ref (instructions_by_name, name, SCM_UNDEFINED);
@ -111,7 +112,7 @@ SCM_DEFINE (scm_instruction_list, "instruction-list", 0, 0, 0,
SCM list = SCM_EOL;
int i;
struct scm_instruction *ip = fetch_instruction_table ();
for (i = 0; i < scm_op_last; i++)
for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
if (ip[i].name)
list = scm_cons (ip[i].symname, list);
return scm_reverse_x (list, SCM_EOL);
@ -182,7 +183,7 @@ SCM_DEFINE (scm_opcode_to_instruction, "opcode->instruction", 1, 0, 0,
SCM_MAKE_VALIDATE (1, op, I_INUMP);
opcode = SCM_I_INUM (op);
if (opcode < scm_op_last)
if (opcode >= 0 && opcode < SCM_VM_NUM_INSTRUCTIONS)
ret = fetch_instruction_table ()[opcode].symname;
if (scm_is_false (ret))

1
libguile/instructions.h
View file

@ -31,7 +31,6 @@ enum scm_opcode {
#include <libguile/vm-i-scheme.i>
#include <libguile/vm-i-loader.i>
#undef VM_INSTRUCTION_TO_OPCODE
scm_op_last = SCM_VM_NUM_INSTRUCTIONS
};
SCM_API SCM scm_instruction_list (void);