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Fetch operands of binary operators in left-to-right order #23108

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Merged
merged 3 commits into from
Jul 15, 2025
Merged

Fetch operands of binary operators in left-to-right order #23108

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899def9
pp.c, pp_hot.c: Reorder SvXV_nomg() to fetch operands in left-to-righ…
t-a-k Feb 26, 2025
4ce65f7
pp_add, pp_subtract: Unify TARGn(<result>, 1) calls into a single call
t-a-k Dec 13, 2024
b06fe6b
perldelta.pod: describe the bug where "0+" methods were sometimes cal…
t-a-k Apr 3, 2025
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19 changes: 19 additions & 0 deletions pod/perldelta.pod
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Original file line number Diff line number Diff line change
Expand Up @@ -220,6 +220,14 @@ XXX Changes (i.e. rewording) of diagnostic messages go here

XXX Describe change here

=item *

L<Use of uninitialized value%s|perldiag/"Use of uninitialized value%s">

This warning was issued in the reverse order (right-to-left) when both
operands of a binary operator are uninitialized values. This is now
fixed to be consistent with evaluation order of operands.

=back

=head1 Utility Changes
Expand Down Expand Up @@ -368,6 +376,17 @@ manager will later use a regex to expand these into links.

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In the commit message s/thange/change/

XXX

=item *

When both operands of arithmetic operators (C<+>, C<->, etc.) are
L<overload>ed objects which have no method for that operator but have
a C<0+> method and the C<fallback> option set to TRUE,
perl will normally call the C<0+> method for the left operand first
and then call one for the right operand, i.e. in the same order
with operand evaluation order.
But if C<S<use integer;>> is in effect, the C<0+> methods used to be
called in wrong (reverse) order.

=back

=head1 Known Problems
Expand Down
54 changes: 26 additions & 28 deletions pp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1483,8 +1483,8 @@ PP(pp_multiply)
} /* SvIOK(svr) */
#endif
{
NV right = SvNV_nomg(svr);
NV left = SvNV_nomg(svl);
NV right = SvNV_nomg(svr);
NV result = left * right;

#if defined(__sgi) && defined(USE_LONG_DOUBLE) && LONG_DOUBLEKIND == LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_BE_BE && NVSIZE == 16
Expand Down Expand Up @@ -1611,8 +1611,8 @@ PP(pp_divide)
} /* one operand wasn't SvIOK */
#endif /* PERL_TRY_UV_DIVIDE */
{
NV right = SvNV_nomg(svr);
NV left = SvNV_nomg(svl);
NV right = SvNV_nomg(svr);
#if defined(NAN_COMPARE_BROKEN) && defined(Perl_isnan)
if (! Perl_isnan(right) && right == 0.0)
#else
Expand Down Expand Up @@ -1919,7 +1919,7 @@ PP(pp_subtract)

SV *svr = PL_stack_sp[0];
SV *svl = PL_stack_sp[-1];

NV nv;

#ifdef PERL_PRESERVE_IVUV

Expand Down Expand Up @@ -2050,7 +2050,8 @@ PP(pp_subtract)
TARGi(NEGATE_2IV(result), 1);
else {
/* result valid, but out of range for IV. */
TARGn(-(NV)result, 1);
nv = -(NV)result;
goto ret_nv;
}
}
goto ret;
Expand All @@ -2060,17 +2061,14 @@ PP(pp_subtract)
#else
useleft = USE_LEFT(svl);
#endif
{
NV value = SvNV_nomg(svr);

if (!useleft) {
/* left operand is undef, treat as zero - value */
TARGn(-value, 1);
goto ret;
}
TARGn(SvNV_nomg(svl) - value, 1);
goto ret;
}
/* If left operand is undef, treat as zero - value */
nv = useleft ? SvNV_nomg(svl) : 0.0;
/* Separate statements here to ensure SvNV_nomg(svl) is evaluated
before SvNV_nomg(svr) */
nv -= SvNV_nomg(svr);
ret_nv:
TARGn(nv, 1);

ret:
rpp_replace_2_1_NN(targ);
Expand Down Expand Up @@ -2356,8 +2354,8 @@ Perl_do_ncmp(pTHX_ SV* const left, SV * const right)
}
#endif
{
NV const rnv = SvNV_nomg(right);
NV const lnv = SvNV_nomg(left);
NV const rnv = SvNV_nomg(right);

#if defined(NAN_COMPARE_BROKEN) && defined(Perl_isnan)
if (Perl_isnan(lnv) || Perl_isnan(rnv)) {
Expand Down Expand Up @@ -2888,8 +2886,8 @@ PP(pp_i_multiply)
if (rpp_try_AMAGIC_2(mult_amg, AMGf_assign))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

TARGi((IV)((UV)left * (UV)right), 1);
rpp_replace_2_1_NN(targ);
Expand All @@ -2910,10 +2908,10 @@ PP(pp_i_divide)
SV *left = PL_stack_sp[-1];

{
IV num = SvIV_nomg(left);
IV value = SvIV_nomg(right);
if (value == 0)
DIE(aTHX_ "Illegal division by zero");
IV num = SvIV_nomg(left);

/* avoid FPE_INTOVF on some platforms when num is IV_MIN */
if (value == -1)
Expand All @@ -2936,8 +2934,8 @@ PP(pp_i_modulo)
if (rpp_try_AMAGIC_2(modulo_amg, AMGf_assign))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

{
if (!right)
Expand All @@ -2962,9 +2960,9 @@ PP(pp_i_add)
if (rpp_try_AMAGIC_2(add_amg, AMGf_assign))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
SV *leftsv = PL_stack_sp[-1];
IV left = USE_LEFT(leftsv) ? SvIV_nomg(leftsv) : 0;
IV right = SvIV_nomg(PL_stack_sp[0]);

TARGi((IV)((UV)left + (UV)right), 1);
rpp_replace_2_1_NN(targ);
Expand All @@ -2981,9 +2979,9 @@ PP(pp_i_subtract)
if (rpp_try_AMAGIC_2(subtr_amg, AMGf_assign))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
SV *leftsv = PL_stack_sp[-1];
IV left = USE_LEFT(leftsv) ? SvIV_nomg(leftsv) : 0;
IV right = SvIV_nomg(PL_stack_sp[0]);

TARGi((IV)((UV)left - (UV)right), 1);
rpp_replace_2_1_NN(targ);
Expand All @@ -2996,8 +2994,8 @@ PP(pp_i_lt)
if (rpp_try_AMAGIC_2(lt_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left < right));
return NORMAL;
Expand All @@ -3009,8 +3007,8 @@ PP(pp_i_gt)
if (rpp_try_AMAGIC_2(gt_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left > right));
return NORMAL;
Expand All @@ -3022,8 +3020,8 @@ PP(pp_i_le)
if (rpp_try_AMAGIC_2(le_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left <= right));
return NORMAL;
Expand All @@ -3035,8 +3033,8 @@ PP(pp_i_ge)
if (rpp_try_AMAGIC_2(ge_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left >= right));
return NORMAL;
Expand All @@ -3048,8 +3046,8 @@ PP(pp_i_eq)
if (rpp_try_AMAGIC_2(eq_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left == right));
return NORMAL;
Expand All @@ -3061,8 +3059,8 @@ PP(pp_i_ne)
if (rpp_try_AMAGIC_2(ne_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);

rpp_replace_2_IMM_NN(boolSV(left != right));
return NORMAL;
Expand All @@ -3075,8 +3073,8 @@ PP(pp_i_ncmp)
if (rpp_try_AMAGIC_2(ncmp_amg, 0))
return NORMAL;

IV right = SvIV_nomg(PL_stack_sp[0]);
IV left = SvIV_nomg(PL_stack_sp[-1]);
IV right = SvIV_nomg(PL_stack_sp[0]);


{
Expand Down Expand Up @@ -3122,8 +3120,8 @@ PP(pp_atan2)
if (rpp_try_AMAGIC_2(atan2_amg, 0))
return NORMAL;

NV right = SvNV_nomg(PL_stack_sp[0]);
NV left = SvNV_nomg(PL_stack_sp[-1]);
NV right = SvNV_nomg(PL_stack_sp[0]);

TARGn(Perl_atan2(left, right), 1);
rpp_replace_2_1_NN(targ);
Expand Down
21 changes: 10 additions & 11 deletions pp_hot.c
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Expand Up @@ -1811,6 +1811,7 @@ PP(pp_add)
SV *targ = (PL_op->op_flags & OPf_STACKED)
? PL_stack_sp[-1]
: PAD_SV(PL_op->op_targ);
NV nv;

if (rpp_try_AMAGIC_2(add_amg, AMGf_assign|AMGf_numeric))
return NORMAL;
Expand Down Expand Up @@ -1994,7 +1995,8 @@ PP(pp_add)
TARGi(NEGATE_2IV(result), 1);
else {
/* result valid, but out of range for IV. */
TARGn(-(NV)result, 1);
nv = -(NV)result;
goto ret_nv;
}
}
goto ret;
Expand All @@ -2006,16 +2008,13 @@ PP(pp_add)
useleft = USE_LEFT(svl);
#endif

{
NV value = SvNV_nomg(svr);
if (!useleft) {
/* left operand is undef, treat as zero. + 0.0 is identity. */
TARGn(value, 1);
}
else {
TARGn(value + SvNV_nomg(svl), 1);
}
}
/* If left operand is undef, treat as zero. */
nv = useleft ? SvNV_nomg(svl) : 0.0;
/* Separate statements here to ensure SvNV_nomg(svl) is evaluated
before SvNV_nomg(svr) */
nv += SvNV_nomg(svr);
ret_nv:
TARGn(nv, 1);

ret:
rpp_replace_2_1_NN(targ);
Expand Down
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