From 2ef427168818ce04b03cecb7b739f9db0156e3e4 Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Thu, 3 Jan 2019 15:51:37 +0100 Subject: Only build libm with -fno-math-errno (bug 24024) Commit 1294b1892e ("Add support for sqrt asm redirects") added the -fno-math-errno flag to build most of the glibc in order to enable GCC to inline math functions. Due to GCC bug #88576, saving and restoring errno around calls to malloc are optimized-out. In turn this causes strerror to set errno to ENOMEM if it get passed an invalid error number and if malloc sets errno to ENOMEM (which might happen even if it succeeds). This is not allowed by POSIX. This patch changes the build flags, building only libm with -fno-math-errno and all the remaining code with -fno-math-errno. This should be safe as libm doesn't contain any code saving and restoring errno around malloc. This patch can probably be reverted once the GCC bug is fixed and available in stable releases. Tested on x86-64, no regression in the testsuite. Changelog: [BZ #24024] * Makeconfig: Build libm with -fno-math-errno but build the remaining code with -fmath-errno. * string/Makefile [$(build-shared)] (tests): Add test-strerror-errno. [$(build-shared)] (LDLIBS-test-strerror-errno): New variable. * string/test-strerror-errno.c: New file. --- string/test-strerror-errno.c | 61 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 string/test-strerror-errno.c (limited to 'string/test-strerror-errno.c') diff --git a/string/test-strerror-errno.c b/string/test-strerror-errno.c new file mode 100644 index 0000000000..8e744e7ed9 --- /dev/null +++ b/string/test-strerror-errno.c @@ -0,0 +1,61 @@ +/* BZ #24024 strerror and errno test. + + Copyright (C) 2019 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 + . */ + +#include +#include +#include + +#include +#include + +/* malloc is allowed to change errno to a value different than 0, even when + there is no actual error. This happens for example when the memory + allocation through sbrk fails. Simulate this by interposing our own + malloc implementation which sets errno to ENOMEM and calls the original + malloc. */ +void +*malloc (size_t size) +{ + static void *(*real_malloc) (size_t size); + + if (!real_malloc) + real_malloc = dlsym (RTLD_NEXT, "malloc"); + + errno = ENOMEM; + + return (*real_malloc) (size); +} + +/* strerror must not change the value of errno. Unfortunately due to GCC bug + #88576, this happens when -fmath-errno is used. This simple test checks + that it doesn't happen. */ +static int +do_test (void) +{ + char *msg; + + errno = 0; + msg = strerror (-3); + (void) msg; + TEST_COMPARE (errno, 0); + + return 0; +} + +#include -- cgit 1.4.1