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* inline.h (scm_double_cell): prevent reordering of statements

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with any following code (for GCC 3 strict-aliasing).
	* numbers.c (scm_make_real), num2float.i.c (FLOAT2NUM): removed
	the earlier version of the reordering prevention.
This commit is contained in:
Gary Houston 2002-09-24 22:21:01 +00:00
parent c15030bebf
commit 3553e1d1f0
4 changed files with 30 additions and 14 deletions
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7
libguile/ChangeLog
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@ -1,3 +1,10 @@
2002-09-24 Gary Houston <ghouston@arglist.com>
* inline.h (scm_double_cell): prevent reordering of statements
with any following code (for GCC 3 strict-aliasing).
* numbers.c (scm_make_real), num2float.i.c (FLOAT2NUM): removed
the earlier version of the reordering prevention.
2002-09-19 Han-Wen Nienhuys <hanwen@cs.uu.nl>
* inline.h (scm_double_cell): move SET_GCMARK set out of if body.

20
libguile/inline.h
View file

@ -213,6 +213,26 @@ scm_double_cell (scm_t_bits car, scm_t_bits cbr,
/* see above. */
SCM_SET_GC_MARK (z);
#endif
/* When this function is inlined, it's possible that the last
SCM_GC_SET_CELL_WORD above will be adjacent to a following
initialization of z. E.g., it occurred in scm_make_real. GCC
from around version 3 (e.g., certainly 3.2) began taking
advantage of strict C aliasing rules which say that it's OK to
interchange the initialization above and the one below when the
pointer types appear to differ sufficiently. We don't want that,
of course. GCC allows this behaviour to be disabled with the
-fno-strict-aliasing option, but would also need to be supplied
by Guile users. Instead, the following statements prevent the
reordering.
*/
#ifdef __GNUC__
asm volatile ("" : : : "memory");
#else
/* portable version, just in case any other compiler does the same
thing. */
scm_remember_upto_here_1 (z);
#endif
return z;

8
libguile/num2float.i.c
View file

@ -31,12 +31,8 @@ NUM2FLOAT (SCM num, unsigned long int pos, const char *s_caller)
SCM
FLOAT2NUM (FTYPE n)
{
SCM z;
z = scm_double_cell (scm_tc16_real, 0, 0, 0);
/*
See scm_make_real().
*/
scm_remember_upto_here_1 (z);
SCM z = scm_double_cell (scm_tc16_real, 0, 0, 0);
SCM_REAL_VALUE (z) = n;
return z;
}

9
libguile/numbers.c
View file

@ -3013,15 +3013,8 @@ SCM_DEFINE (scm_string_to_number, "string->number", 1, 1, 0,
SCM
scm_make_real (double x)
{
SCM z;
z = scm_double_cell (scm_tc16_real, 0, 0, 0);
SCM z = scm_double_cell (scm_tc16_real, 0, 0, 0);
/*
scm_double_cell is inlined. strict C aliasing rules say that it's
OK to interchange the initialization above and the one below. We
don't want that, of course.
*/
scm_remember_upto_here_1 (z);
SCM_REAL_VALUE (z) = x;
return z;
}