diff options
| -rw-r--r-- | sysdeps/x86/Makefile | 4 | ||||
| -rw-r--r-- | sysdeps/x86/ldbl2mpn.c | 8 | ||||
| -rw-r--r-- | sysdeps/x86/tst-ldbl-nonnormal-printf.c | 52 |
3 files changed, 64 insertions, 0 deletions
diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile index c369faf00d..081cc72e93 100644 --- a/sysdeps/x86/Makefile +++ b/sysdeps/x86/Makefile @@ -11,6 +11,10 @@ tests += tst-get-cpu-features tst-get-cpu-features-static \ tests-static += tst-get-cpu-features-static endif +ifeq ($(subdir),math) +tests += tst-ldbl-nonnormal-printf +endif # $(subdir) == math + ifeq ($(subdir),setjmp) gen-as-const-headers += jmp_buf-ssp.sym sysdep_routines += __longjmp_cancel diff --git a/sysdeps/x86/ldbl2mpn.c b/sysdeps/x86/ldbl2mpn.c index ec8464eef7..23afedfb67 100644 --- a/sysdeps/x86/ldbl2mpn.c +++ b/sysdeps/x86/ldbl2mpn.c @@ -115,6 +115,14 @@ __mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size, && res_ptr[N - 1] == 0) /* Pseudo zero. */ *expt = 0; + else + /* Unlike other floating point formats, the most significant bit + is explicit and expected to be set for normal numbers. Set it + in case it is cleared in the input. Otherwise, callers will + not be able to produce the expected multi-precision integer + layout by shifting. */ + res_ptr[N - 1] |= (mp_limb_t) 1 << (LDBL_MANT_DIG - 1 + - ((N - 1) * BITS_PER_MP_LIMB)); return N; } diff --git a/sysdeps/x86/tst-ldbl-nonnormal-printf.c b/sysdeps/x86/tst-ldbl-nonnormal-printf.c new file mode 100644 index 0000000000..54381ece0b --- /dev/null +++ b/sysdeps/x86/tst-ldbl-nonnormal-printf.c @@ -0,0 +1,52 @@ +/* Test printf with x86-specific non-normal long double value. + Copyright (C) 2020 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 <stdio.h> +#include <string.h> +#include <support/check.h> + +/* Fill the stack with non-zero values. This makes a crash in + snprintf more likely. */ +static void __attribute__ ((noinline, noclone)) +fill_stack (void) +{ + char buffer[65536]; + memset (buffer, 0xc0, sizeof (buffer)); + asm ("" ::: "memory"); +} + +static int +do_test (void) +{ + fill_stack (); + + long double value; + memcpy (&value, "\x00\x04\x00\x00\x00\x00\x00\x00\x00\x04", 10); + + char buf[30]; + int ret = snprintf (buf, sizeof (buf), "%Lg", value); + TEST_COMPARE (ret, strlen (buf)); + if (strcmp (buf, "nan") != 0) + /* If snprintf does not recognize the non-normal number as a NaN, + it has added the missing explicit MSB. */ + TEST_COMPARE_STRING (buf, "3.02201e-4624"); + return 0; +} + +#include <support/test-driver.c> |