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From: "bruno at clisp dot org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug math/31022] New: feupdateenv (FE_DFL_ENV) crashes on riscv
Date: Wed, 01 Nov 2023 17:02:49 +0000
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X-Bugzilla-Component: math
X-Bugzilla-Version: 2.37
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31022

            Bug ID: 31022
           Summary: feupdateenv (FE_DFL_ENV) crashes on riscv
           Product: glibc
           Version: 2.37
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: bruno at clisp dot org
  Target Milestone: ---

ISO C 23 =C2=A7 7.6.6.4 says about feupdateenv:
"The argument envp shall point to an object set by a call to feholdexcept or
fegetenv, or equal a dynamic floating-point environment macro."

This means, it is valid to call feupdateenv (FE_DFL_ENV).

But this call crashes with SIGSEGV on riscv.

How to reproduce:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D foo.c =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
#include <fenv.h>

int
main ()
{
  return feupdateenv (FE_DFL_ENV) !=3D 0;
}
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
$ gcc -Wall foo.c -lm
$ ./a.out
Segmentation fault (core dumped)

The place where it crashes is obviously at
glibc/sysdeps/riscv/rvf/fenv_private.h line 126:

static __always_inline void
libc_feupdateenv_riscv (const fenv_t *envp)
{
  _FPU_SETCW (*envp | riscv_getflags ());   // <=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D HERE
}

with envp being 0xffffffffffffffff.

--=20
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