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guix/gnu/packages/patches/quickjs-ng-64-bits-precision-on-i686.patch
Ashvith Shetty 89e8c55f2b gnu: quickjs-ng: Resolve build issue with x86-32 platform. 
* gnu/packages/javascript.scm (quickjs-ng):
[source]: Add quickjs-ng-64-bits-precision-on-i686.patch and
quickjs-ng-fix-atomics.pause-on-32-bit.patch patches.
[arguments]<#:tests?>: Enable them.
* quickjs-ng-64-bits-precision-on-i686.patch,
* gnu/packages/patches/quickjs-ng-fix-atomics.pause-on-32-bit.patch: New
files.
* gnu/local.mk (dist_patch_DATA): Add them.

Change-Id: I94be4c85725c9fe7780c1b2e2186411719051b56
Signed-off-by: Efraim Flashner <efraim@flashner.co.il>
2026-01-14 13:04:25 +02:00

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From bd4ee689a854252665fd607758f078d930fbc4c8 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Fri, 21 Nov 2025 11:56:28 +0100
Subject: [PATCH] Fix JS number rounding on x87 (#1244)
Disable 80-bits extended precision, use standard 64-bits precision.
The extra precision affects rounding and is user-observable, meaning
it causes test262 tests to fail.
The rounding mode is a per-CPU (or, more accurately, per-FPU) property,
and since quickjs is often used as a library, take care to tweak the FPU
control word before sensitive operations, and restore it afterwards.
Only affects x87. SSE is IEEE-754 conforming.
Fixes: https://github.com/quickjs-ng/quickjs/issues/1236
---
.github/workflows/ci.yml | 4 ++--
cutils.h | 19 +++++++++++++++++++
quickjs.c | 34 +++++++++++++++++++++++++++++-----
3 files changed, 50 insertions(+), 7 deletions(-)
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d1efee1b9..c722b517d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -58,7 +58,7 @@ jobs:
- { os: ubuntu-latest, configType: asan+ubsan, runTest262: true }
- { os: ubuntu-latest, configType: msan }
- { os: ubuntu-latest, configType: tcc }
- - { os: ubuntu-latest, arch: x86 }
+ - { os: ubuntu-latest, arch: x86, runTest262: true }
- { os: ubuntu-latest, arch: riscv64 }
- { os: ubuntu-latest, arch: s390x }
@@ -97,7 +97,7 @@ jobs:
uses: jirutka/setup-alpine@v1
with:
arch: ${{ matrix.config.arch }}
- packages: "build-base make cmake"
+ packages: "build-base make cmake git"
- name: uname
run: uname -a
diff --git a/cutils.h b/cutils.h
index 5129c3cb2..f5d2a8bce 100644
--- a/cutils.h
+++ b/cutils.h
@@ -634,6 +634,25 @@ int js_thread_join(js_thread_t thrd);
#endif /* !defined(EMSCRIPTEN) && !defined(__wasi__) */
+// JS requires strict rounding behavior. Turn on 64-bits double precision
+// and disable x87 80-bits extended precision for intermediate floating-point
+// results. 0x300 is extended precision, 0x200 is double precision.
+// Note that `*&cw` in the asm constraints looks redundant but isn't.
+#if defined(__i386__) && !defined(_MSC_VER)
+#define JS_X87_FPCW_SAVE_AND_ADJUST(cw) \
+ unsigned short cw; \
+ __asm__ __volatile__("fnstcw %0" : "=m"(*&cw)); \
+ do { \
+ unsigned short t = 0x200 | (cw & ~0x300); \
+ __asm__ __volatile__("fldcw %0" : /*empty*/ : "m"(*&t)); \
+ } while (0)
+#define JS_X87_FPCW_RESTORE(cw) \
+ __asm__ __volatile__("fldcw %0" : /*empty*/ : "m"(*&cw))
+#else
+#define JS_X87_FPCW_SAVE_AND_ADJUST(cw)
+#define JS_X87_FPCW_RESTORE(cw)
+#endif
+
#ifdef __cplusplus
} /* extern "C" { */
#endif
diff --git a/quickjs.c b/quickjs.c
index 3970bb247..7900c5e3d 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -13395,12 +13395,17 @@ static int js_is_array(JSContext *ctx, JSValueConst val)
static double js_math_pow(double a, double b)
{
+ double d;
+
if (unlikely(!isfinite(b)) && fabs(a) == 1) {
/* not compatible with IEEE 754 */
- return NAN;
+ d = NAN;
} else {
- return pow(a, b);
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
+ d = pow(a, b);
+ JS_X87_FPCW_RESTORE(fpcw);
}
+ return d;
}
JSValue JS_NewBigInt64(JSContext *ctx, int64_t v)
@@ -13820,11 +13825,15 @@ static no_inline __exception int js_binary_arith_slow(JSContext *ctx, JSValue *s
}
break;
case OP_div:
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
sp[-2] = js_number((double)v1 / (double)v2);
+ JS_X87_FPCW_RESTORE(fpcw);
return 0;
case OP_mod:
if (v1 < 0 || v2 <= 0) {
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
sp[-2] = js_number(fmod(v1, v2));
+ JS_X87_FPCW_RESTORE(fpcw);
return 0;
} else {
v = (int64_t)v1 % (int64_t)v2;
@@ -13888,6 +13897,7 @@ static no_inline __exception int js_binary_arith_slow(JSContext *ctx, JSValue *s
if (JS_ToFloat64Free(ctx, &d2, op2))
goto exception;
handle_float64:
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
switch(op) {
case OP_sub:
dr = d1 - d2;
@@ -13907,6 +13917,7 @@ static no_inline __exception int js_binary_arith_slow(JSContext *ctx, JSValue *s
default:
abort();
}
+ JS_X87_FPCW_RESTORE(fpcw);
sp[-2] = js_float64(dr);
}
return 0;
@@ -14023,7 +14034,9 @@ static no_inline __exception int js_add_slow(JSContext *ctx, JSValue *sp)
}
if (JS_ToFloat64Free(ctx, &d2, op2))
goto exception;
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
sp[-2] = js_float64(d1 + d2);
+ JS_X87_FPCW_RESTORE(fpcw);
}
return 0;
exception:
@@ -17998,8 +18011,10 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValueConst func_obj,
sp[-2] = js_int32(r);
sp--;
} else if (JS_VALUE_IS_BOTH_FLOAT(op1, op2)) {
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
sp[-2] = js_float64(JS_VALUE_GET_FLOAT64(op1) +
JS_VALUE_GET_FLOAT64(op2));
+ JS_X87_FPCW_RESTORE(fpcw);
sp--;
} else {
add_slow:
@@ -18066,8 +18081,10 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValueConst func_obj,
sp[-2] = js_int32(r);
sp--;
} else if (JS_VALUE_IS_BOTH_FLOAT(op1, op2)) {
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
sp[-2] = js_float64(JS_VALUE_GET_FLOAT64(op1) -
JS_VALUE_GET_FLOAT64(op2));
+ JS_X87_FPCW_RESTORE(fpcw);
sp--;
} else {
goto binary_arith_slow;
@@ -18098,7 +18115,9 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValueConst func_obj,
sp[-2] = js_int32(r);
sp--;
} else if (JS_VALUE_IS_BOTH_FLOAT(op1, op2)) {
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
d = JS_VALUE_GET_FLOAT64(op1) * JS_VALUE_GET_FLOAT64(op2);
+ JS_X87_FPCW_RESTORE(fpcw);
mul_fp_res:
sp[-2] = js_float64(d);
sp--;
@@ -52277,7 +52296,9 @@ static double set_date_fields(double fields[minimum_length(7)], int is_local) {
int yi, mi, i;
int64_t days;
volatile double temp; /* enforce evaluation order */
+ double d = NAN;
+ JS_X87_FPCW_SAVE_AND_ADJUST(fpcw);
/* emulate 21.4.1.15 MakeDay ( year, month, date ) */
y = fields[0];
m = fields[1];
@@ -52287,7 +52308,7 @@ static double set_date_fields(double fields[minimum_length(7)], int is_local) {
if (mn < 0)
mn += 12;
if (ym < -271821 || ym > 275760)
- return NAN;
+ goto out;
yi = ym;
mi = mn;
@@ -52319,14 +52340,17 @@ static double set_date_fields(double fields[minimum_length(7)], int is_local) {
/* emulate 21.4.1.16 MakeDate ( day, time ) */
tv = (temp = day * 86400000) + time; /* prevent generation of FMA */
if (!isfinite(tv))
- return NAN;
+ goto out;
/* adjust for local time and clip */
if (is_local) {
int64_t ti = tv < INT64_MIN ? INT64_MIN : tv >= 0x1p63 ? INT64_MAX : (int64_t)tv;
tv += getTimezoneOffset(ti) * 60000;
}
- return time_clip(tv);
+ d = time_clip(tv);
+out:
+ JS_X87_FPCW_RESTORE(fpcw);
+ return d;
}
static JSValue get_date_field(JSContext *ctx, JSValueConst this_val,
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