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* eval.c (safe_setjmp): New function: trivial wrapper for setjmp.

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(SCM_CEVAL, SCM_APPLY): Call it, instead of setjmp, to make sure
that values of automatic variables are preserved.  See comments
for safe_setjmp for details.
This commit is contained in:
Jim Blandy 1997-02-04 23:30:07 +00:00
parent c4314b4ff4
commit c4ac4d8862
1 changed files with 35 additions and 7 deletions
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42
libguile/eval.c
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@ -1158,6 +1158,34 @@ scm_eval_args (l, env)
} }
return res; return res;
} }
/* The SCM_CEVAL and SCM_APPLY functions use this function instead of
calling setjmp directly, to make sure that local variables don't
have their values clobbered by a longjmp.
According to Harbison & Steele, "Automatic variables local to the
function containing setjmp are guaranteed to have their correct
value in ANSI C only if they have a volatile-qualified type or if
their values were not changed between the original call to setjmp
and the corresponding longjmp call."
SCM_CEVAL and SCM_APPLY are too complex for me to see how to meet
the second condition, and making x and env volatile would be a
speed problem, so we'll just trivially meet the first, by having no
"automatic variables local to the function containing setjmp." */
static int
safe_setjmp (jmp_buf env)
{
/* I think ANSI requires us to write the function this way, instead
of just saying "return setjmp (env)". Maybe I'm being silly.
See Harbison & Steele, third edition, p. 353. */
int val;
val = setjmp (env);
return val;
}
#endif /* !DEVAL */ #endif /* !DEVAL */
@ -1204,7 +1232,7 @@ scm_eval_args (l, env)
else\ else\
{\ {\
scm_make_cont (&tmp);\ scm_make_cont (&tmp);\
if (!setjmp (SCM_JMPBUF (tmp)))\ if (!safe_setjmp (SCM_JMPBUF (tmp)))\
scm_ithrow (scm_i_apply_frame, scm_cons2 (tmp, tail, SCM_EOL), 0);\ scm_ithrow (scm_i_apply_frame, scm_cons2 (tmp, tail, SCM_EOL), 0);\
}\ }\
}\ }\
@ -1371,7 +1399,7 @@ loop:
SCM_RESET_DEBUG_MODE; SCM_RESET_DEBUG_MODE;
SCM_CLEAR_TRACED_FRAME (debug); SCM_CLEAR_TRACED_FRAME (debug);
scm_make_cont (&t.arg1); scm_make_cont (&t.arg1);
if (!setjmp (SCM_JMPBUF (t.arg1))) if (!safe_setjmp (SCM_JMPBUF (t.arg1)))
scm_ithrow (scm_i_exit_tail, scm_cons (t.arg1, SCM_EOL), 0); scm_ithrow (scm_i_exit_tail, scm_cons (t.arg1, SCM_EOL), 0);
} }
} }
@ -1400,7 +1428,7 @@ start:
else else
{ {
scm_make_cont (&t.arg1); scm_make_cont (&t.arg1);
if (setjmp (SCM_JMPBUF (t.arg1))) if (safe_setjmp (SCM_JMPBUF (t.arg1)))
{ {
x = SCM_THROW_VALUE (t.arg1); x = SCM_THROW_VALUE (t.arg1);
if (SCM_IMP (x)) if (SCM_IMP (x))
@ -1726,7 +1754,7 @@ dispatch:
case (SCM_ISYMNUM (SCM_IM_CONT)): case (SCM_ISYMNUM (SCM_IM_CONT)):
scm_make_cont (&t.arg1); scm_make_cont (&t.arg1);
if (setjmp (SCM_JMPBUF (t.arg1))) if (safe_setjmp (SCM_JMPBUF (t.arg1)))
{ {
SCM val; SCM val;
val = SCM_THROW_VALUE (t.arg1); val = SCM_THROW_VALUE (t.arg1);
@ -2185,7 +2213,7 @@ exit:
else else
{ {
scm_make_cont (&t.arg1); scm_make_cont (&t.arg1);
if (setjmp (SCM_JMPBUF (t.arg1))) if (safe_setjmp (SCM_JMPBUF (t.arg1)))
{ {
proc = SCM_THROW_VALUE (t.arg1); proc = SCM_THROW_VALUE (t.arg1);
goto ret; goto ret;
@ -2345,7 +2373,7 @@ SCM_APPLY (proc, arg1, args)
else else
{ {
scm_make_cont (&tmp); scm_make_cont (&tmp);
if (setjmp (SCM_JMPBUF (tmp))) if (safe_setjmp (SCM_JMPBUF (tmp)))
goto entap; goto entap;
} }
scm_ithrow (scm_i_enter_frame, scm_cons (tmp, SCM_EOL), 0); scm_ithrow (scm_i_enter_frame, scm_cons (tmp, SCM_EOL), 0);
@ -2492,7 +2520,7 @@ exit:
else else
{ {
scm_make_cont (&arg1); scm_make_cont (&arg1);
if (setjmp (SCM_JMPBUF (arg1))) if (safe_setjmp (SCM_JMPBUF (arg1)))
{ {
proc = SCM_THROW_VALUE (arg1); proc = SCM_THROW_VALUE (arg1);
goto ret; goto ret;