math: x86 trunc traps when FE_INEXACT is enabled (BZ 31603)

The implementations of trunc functions using x87 floating point (i386 and
x86_64 long double only) traps when FE_INEXACT is enabled.  Although
this is a GNU extension outside the scope of the C standard, other
architectures that also support traps do not show this behavior.

The fix moves the implementation to a common one that holds any
exceptions with a 'fnclex' (libc_feholdexcept_setround_387).

Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/sysdeps/i386/fpu/s_truncf.c b/sysdeps/i386/fpu/s_truncf.c
new file mode 100644
index 0000000000..240d3507ef
--- /dev/null
+++ b/sysdeps/i386/fpu/s_truncf.c
@@ -0,0 +1,25 @@
+/* Round to integer, toward zero.  i386 version.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-float.h>
+
+#define FUNC       __truncf
+#define TYPE       float
+#define FE_OPTION  FE_TOWARDZERO
+#include "s_nearestint_387_template.c"
+libm_alias_float (__trunc, trunc)