A large number of the test-ldouble failures seen for ldbl-128ibm are
spurious "underflow" and "inexact" exceptions. These arise from such
exceptions in the underlying arithmetic; unlike other spurious
exceptions from that arithmetic, they do not in general relate to
cases where the returned result is also substantially inaccurate, are
not so readily avoidable by appropriately conditional libgcc patches,
and are widespread enough to be hard to handle through individual
XFAILing of the affected tests.
Thus, this patch documents relaxed accuracy goals for libm functions
for IBM long double and makes libm-test.inc reflect these spurious
exceptions in ldbl-128ibm arithmetic and always allow them in
ldbl-128ibm testing (while still not allowing these exceptions to be
missing where required to be present). Tested for powerpc.
* manual/math.texi (Errors in Math Functions): Document relaxed
accuracy goals for IBM long double.
* math/libm-test.inc (test_exceptions): Always allow spurious
"underflow" and "inexact" exceptions for IBM long double.
In <https://sourceware.org/ml/libc-alpha/2016-01/msg00885.html> I
proposed a minimum Linux kernel version of 3.2 for glibc 2.24, since
Linux 2.6.32 has reached EOL.
In the discussion in February, some concerns were expressed about
compatibility with OpenVZ containers. It's not clear that these are
real issues, given OpenVZ backporting kernel features and faking the
kernel version for guest software, as discussed in
<https://sourceware.org/ml/libc-alpha/2016-02/msg00278.html>. It's
also not clear that supporting running GNU/Linux distributions from
late 2016 (at the earliest) on a kernel series from 2009 is a sensible
expectation. However, as an interim step, this patch increases the
requirement everywhere except x86 / x86_64 (since the controversy was
only about those architectures); the special caveats and settings can
easily be removed later when we're ready to increase the requirements
on x86 / x86_64 (and if someone would like to raise the issue on LWN
as suggested in the previous discussion, that would be welcome). 3.2
kernel headers are required everywhere by this patch.
(x32 already requires 3.4 or later, so is unaffected by this patch.)
As usual for such a change, this patch only changes the configure
scripts and associated documentation. The intent is to follow up with
removal of dead __LINUX_KERNEL_VERSION conditionals. Each __ASSUME_*
or other macro that becomes dead can then be removed independently.
Tested for x86_64 and x86.
* sysdeps/unix/sysv/linux/configure.ac (LIBC_LINUX_VERSION):
Define to 3.2.0.
(arch_minimum_kernel): Likewise.
* sysdeps/unix/sysv/linux/configure: Regenerated.
* sysdeps/unix/sysv/linux/i386/configure.ac (arch_minimum_kernel):
Define to 2.6.32.
* sysdeps/unix/sysv/linux/i386/configure: Regenerated.
* sysdeps/unix/sysv/linux/x86_64/64/configure.ac
(arch_minimum_kernel): Define to 2.6.32.
* sysdeps/unix/sysv/linux/x86_64/64/configure: Regenerated.
* README: Document Linux 3.2 requirement.
* manual/install.texi (Linux): Document Linux 3.2 headers
requirement.
* INSTALL: Regenerated.
This patch updates texinfo.tex, config.guess, config.sub and
move-if-change from their respective upstream sources.
* manual/texinfo.tex: Update to version 2016-01-04.21 with
trailing whitespace removed.
* scripts/config.guess: Update to version 2016-01-01.
* scripts/config.sub: Update to version 2016-01-01.
* scripts/move-if-change: Update from gnulib.
Various Linux kernel syscalls have become obsolete over time.
Specifically, the following are obsolete in all kernel versions
supported by glibc, are not present for architectures more recently
added to the kernel, and as such, the wrapper functions for them
should be compat symbols, not in static libc and not available for new
links with shared libc.
* bdflush: in Linux 2.6, does nothing if present.
* create_module get_kernel_syms query_module: Linux 2.4 module
interface, syscalls not present in Linux 2.6.
* uselib: part of the mechanism for loading a.out shared libraries,
irrelevant with ELF.
This patch adds support for syscalls.list to list syscall aliases of
the form NAME@VERSION:OBSOLETED, with SHLIB_COMPAT conditionals being
generated for such aliases. Those five syscalls are then made into
compat symbols (obsoleted in glibc 2.23, so future ports won't have
these symbols at all), with the header <sys/kdaemon.h> declaring
bdflush being removed. When we move to 3.2 as minimum kernel version,
the same can be done for nfsservctl (removed in Linux 3.1) as well.
Tested for x86_64 and x86 (testsuite, as well as checking that the
symbols in question indeed become compat symbols, that they are indeed
omitted from static libc, and that the generated SHLIB_COMPAT
conditionals look right).
[BZ #18472]
* sysdeps/unix/Makefile ($(objpfx)stub-syscalls.c): Handle entries
for the form NAME@VERSION:OBSOLETED and generate SHLIB_COMPAT
conditionals for them.
* sysdeps/unix/make-syscalls.sh (emit_weak_aliases): Likewise.
* sysdeps/unix/sysv/linux/sys/kdaemon.h: Remove file.
* sysdeps/unix/sysv/linux/Makefile (sysdep_headers): Remove
sys/kdaemon.h.
* sysdeps/unix/sysv/linux/syscalls.list (bdflush): Make into
compat-only syscall, obsoleted in glibc 2.23.
(create_module): Likewise.
(get_kernel_syms): Likewise.
(query_module): Likewise.
(uselib): Likewise.
* manual/sysinfo.texi (System Parameters): Do not mention bdflush.
* manual/examples/strncat.c: Remove.
This example was misleading, as the code would have undefined
behavior if "hello" was longer than SIZE. Anyway, the manual
shouldn't encourage strncpy+strncat for this sort of thing.
* manual/string.texi (Copying Strings and Arrays): Split into
three sections Copying Strings and Arrays, Concatenating Strings,
and Truncating Strings, as this section was way too long. All
cross-referenced changed. Add advice about string-truncation
functions. Remove misleading strncat example.
NSS modules which can run in disconnected modes should
return NSS_STATUS_NOTFOUND and SUCCESS in order to follow
best practice for such modules and ensure user applications
can have these modules configured without causing problems
if the data sources are not connected.
* manual/string.texi (Copying and Concatenation): Fix typos in
sample implementations of strncat and wcsncat, by having them use
the old value of the destination length, not the new one.
* manual/string.texi (String and Array Utilities):
Distinguish more carefully among bytes, multibyte characters,
and wide characters. Use "byte" when talking about C 'char',
to distinguish it more clearly from multibyte characters.
Say "wide character" or "multibyte character" instead of
"character", when a wide or multibyte character is intended.
Similarly for "multibyte string" versus "string".
Define these terms more carefully.
With current kernel versions, the check does not reliably detect that
unavailable CPUs are requested, for these reasons:
(1) The kernel will silently ignore non-allowed CPUs, that is, CPUs
which are physically present but disallowed for the thread
based on system configuration.
(2) Similarly, CPU bits which lack an online CPU (possible CPUs)
are ignored.
(3) The existing probing code assumes that the CPU mask size is a
power of two and at least 1024. Neither has it to be a power
of two, nor is the minimum possible value 1024, so the value
determined is often too large. This means that the CPU set
size check in glibc accepts CPU bits beyond the actual hard
system limit.
(4) Future kernel versions may not even have a fixed CPU set size.
After the removal of the probing code, the kernel still returns
EINVAL if no CPU in the requested set remains which can run the
thread after the affinity change.
Applications which care about the exact affinity mask will have
to query it using sched_getaffinity after setting it. Due to the
effects described above, this commit does not change this.
The new tests supersede tst-getcpu, which is removed. This
addresses bug 19164 because the new tests allocate CPU sets
dynamically.
* nptl/check-cpuset.h: Remove.
* nptl/pthread_attr_setaffinity.c (__pthread_attr_setaffinity_new):
Remove CPU set size check.
* nptl/pthread_setattr_default_np.c (pthread_setattr_default_np):
Likewise.
* sysdeps/unix/sysv/linux/check-cpuset.h: Remove.
* sysdeps/unix/sysv/linux/pthread_setaffinity.c
(__kernel_cpumask_size, __determine_cpumask_size): Remove.
(__pthread_setaffinity_new): Remove CPU set size check.
* sysdeps/unix/sysv/linux/sched_setaffinity.c
(__kernel_cpumask_size): Remove.
(__sched_setaffinity_new): Remove CPU set size check.
* manual/threads.texi (Default Thread Attributes): Remove stale
reference to check_cpuset_attr, determine_cpumask_size in comment.
* sysdeps/unix/sysv/linux/Makefile [$(subdir) == posix] (tests):
Remove tst-getcpu. Add tst-affinity, tst-affinity-pid.
[$(subdir) == nptl] (tests): Add tst-thread-affinity-pthread,
tst-thread-affinity-pthread2, tst-thread-affinity-sched.
* sysdeps/unix/sysv/linux/tst-affinity.c: New file.
* sysdeps/unix/sysv/linux/tst-affinity-pid.c: New file.
* sysdeps/unix/sysv/linux/tst-skeleton-affinity.c: New skeleton test file.
* sysdeps/unix/sysv/linux/tst-thread-affinity-sched.c: New file.
* sysdeps/unix/sysv/linux/tst-thread-affinity-pthread.c: New file.
* sysdeps/unix/sysv/linux/tst-thread-affinity-pthread2.c: New file.
* sysdeps/unix/sysv/linux/tst-thread-skeleton-affinity.c: New
skeleton test file.
* sysdeps/unix/sysv/linux/tst-getcpu.c: Remove. Superseded by
tst-affinity-pid.
This patch implements a requirement of GCC 4.7 or later to build
glibc.
This was discussed in the thread starting at
<https://sourceware.org/ml/libc-alpha/2015-08/msg00851.html>.
Concerns were expressed by Mike and David. At
<https://sourceware.org/ml/libc-alpha/2015-10/msg00453.html> I have
provided a 14-patch series showing in outline the cleanups facilitated
by this version requirement, as requested by Mike (this patch is the
first in that series, with the addition of a NEWS entry). Given the
absence of further concerns or alternative proposals for criteria for
updates to this version requirement as requested in
<https://sourceware.org/ml/libc-alpha/2015-10/msg00065.html>, I am
interpreting this as "absence of sustained opposition" under Carlos's
definition at <https://sourceware.org/glibc/wiki/Consensus> and
proposing this patch for inclusion in glibc. I'd like to remind
people testing with 4.6 that if they move to testing with GCC 5 then
it will probably be about four years before they need to update the
compiler they use to test glibc again.
Although on the principles of time-based updates I think a move to
requiring binutils 2.23 would be reasonable, I'm not currently aware
of any cleanups that would facilitate so am not proposing that at this
time (but would expect to propose a move to requiring binutils 2.24 in
a year's time, as that brings features such as AVX512 support that
should allow some conditionals to be cleaned up). If someone thinks a
move to requiring 2.23 would help clean things up for their
architecture, please speak up. (And in general, I suspect there are
lots of architecture-specific configure tests that could be removed on
the basis of current GCC and binutils version requirements, given how
I've found architecture-independent tests obsolete on the basis of
version requirements going back 20 years.)
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).
* configure.ac (libc_cv_compiler_ok): Require GCC 4.7 or later.
* configure: Regenerated.
* manual/install.texi (Tools for Compilation): Document
requirement for GCC 4.7 or later.
* INSTALL: Regenerated.
This automatically-generated patch converts 29 function definitions in
glibc (including one in an example in the manual) from old-style K&R
to prototype-style. Following my other recent such patches, this one
deals with the case of function definitions where one K&R parameter
declaration declares multiple parameters, as in:
void
foo (a, b)
int a, *b;
{
}
Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by the patch).
* crypt/crypt.c (_ufc_doit_r): Convert to prototype-style function
definition.
(_ufc_doit_r): Likewise.
* crypt/crypt_util.c (_ufc_copymem): Likewise.
(_ufc_output_conversion_r): Likewise.
* inet/inet_mkadr.c (__inet_makeaddr): Likewise.
* inet/rcmd.c (rcmd_af): Likewise.
(rcmd): Likewise.
(ruserok_af): Likewise.
(ruserok): Likewise.
(ruserok2_sa): Likewise.
(ruserok_sa): Likewise.
(iruserok_af): Likewise.
(iruserok): Likewise.
(__ivaliduser): Likewise.
(__validuser2_sa): Likewise.
* inet/rexec.c (rexec_af): Likewise.
(rexec): Likewise.
* inet/ruserpass.c (ruserpass): Likewise.
* locale/programs/xmalloc.c (xcalloc): Likewise.
* manual/examples/timeval_subtract.c (timeval_subtract): Likewise.
* math/w_drem.c (__drem): Likewise.
* math/w_dremf.c (__dremf): Likewise.
* math/w_dreml.c (__dreml): Likewise.
* misc/daemon.c (daemon): Likewise.
* resolv/res_debug.c (p_fqnname): Likewise.
* stdlib/div.c (div): Likewise.
* string/memcmp.c (memcmp_bytes): Likewise.
* sunrpc/pmap_rmt.c (pmap_rmtcall): Likewise.
* sunrpc/svc_udp.c (svcudp_bufcreate): Likewise.
The argument order for posix_fallocate64 in the manual
was wrong, it was listed as [fd, len, offset] when it
should have been [fd, offset, len].
Verified io/fcntl.h has the right argument order, and it
does. Verified generated PDF.
In the posix_fallocate description in the manual we list various
drawbacks with the emulation, including the fact that a file opened
with O_APPEND fails with EBADF. Similarly a file opened with O_WRONLY
fails with EBADF. We must be able to emulate a compare-and-swap via
pread/compare/pwrite in order to make the emulation as safe as possible.
It is not acceptable to ignore the read failure because it could result
in significant data loss across all of the blocks. There is no other way
to make this work without a true atomic CAS and SIGBUS handler (which
is looking more attractive as a way to remove the race condition).
This patch adds O_WRONLY to the manual as another bullet to clarify the
limits of the emulation.
Manual looks good in PDF.
Some distros build+install the timezone tools (zic/zdump/tzselect) outside
of glibc and use the upstream package directly. Add a configure flag to
glibc so they can disable install of those tools.
This allows tests to run & pass regardless of the configure flag. Only
the install of them is impacted.
Do not try to generate the manual when perl is unavailable. This
matches the behavior when makeinfo is unavailable. Otherwise the
install step fails when trying to generate the libm section since
it runs a perl script.
This patch adds extra inline functions to change the Program Priority
Register from ISA 2.07.
2015-08-19 Gabriel F. T. Gomes <gftg@linux.vnet.ibm.com>
* sysdeps/powerpc/sys/platform/ppc.h (__ppc_set_ppr_med_high,
__ppc_set_ppr_very_low): New functions.
* manual/platform.texi: Add documentation about
__ppc_set_ppr_med_high and __ppc_set_ppr_very_low.
a non-standard directory specified by the prefix make variable
fails with an error. Since this is an unsupported use case,
this change makes make install fail early and with a descriptive
error message when either the prefix or the exec_prefix make
variable is overridden on the command line.
Here is implementation of cos containing SSE, AVX, AVX2 and AVX512
versions according to Vector ABI which had been discussed in
<https://groups.google.com/forum/#!topic/x86-64-abi/LmppCfN1rZ4>.
Vector math library build and ABI testing enabled by default for x86_64.
* sysdeps/x86_64/fpu/Makefile: New file.
* sysdeps/x86_64/fpu/Versions: New file.
* sysdeps/x86_64/fpu/svml_d_cos_data.S: New file.
* sysdeps/x86_64/fpu/svml_d_cos_data.h: New file.
* sysdeps/x86_64/fpu/svml_d_cos2_core.S: New file.
* sysdeps/x86_64/fpu/svml_d_cos4_core.S: New file.
* sysdeps/x86_64/fpu/svml_d_cos4_core_avx.S: New file.
* sysdeps/x86_64/fpu/svml_d_cos8_core.S: New file.
* sysdeps/x86_64/fpu/svml_d_wrapper_impl.h: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos2_core.S: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos2_core_sse4.S: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos4_core.S: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos4_core_avx2.S: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos8_core.S: New file.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos8_core_avx512.S: New file.
* sysdeps/x86_64/fpu/multiarch/Makefile (libmvec-sysdep_routines): Added
build of SSE, AVX2 and AVX512 IFUNC versions.
* sysdeps/x86/fpu/bits/math-vector.h: Added SIMD declaration for cos.
* math/bits/mathcalls.h: Added cos declaration with __MATHCALL_VEC.
* sysdeps/x86_64/configure.ac: Options for libmvec build.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/sysdep.h (cfi_offset_rel_rsp): New macro.
* sysdeps/unix/sysv/linux/x86_64/libmvec.abilist: New file.
* manual/install.texi (Configuring and compiling): Document
--disable-mathvec.
* INSTALL: Regenerated.
* NEWS: Mention addition of libmvec and x86_64 vector cos.
Handle signed integer overflow correctly. Detect and reject O_APPEND.
Document drawbacks of emulation.
This does not completely address bug 15661, but improves the situation
somewhat.
I was told that Ma Shimao submitted a patch to add envz_remove to the
libc manual, but the patch could not be accepted since he does not
have a copyright assignment in place. I have been woefully behind on
libc-alpha recently and have not seen the patch or the discussion
thread. I have also not read the man page for envz_remove, so
Alexandre Oliva asked me if I could write this independently and post
a patch. The patch below is the result of the same - I have written
it based on the implementation in string/envz.c and Alex told me via
email that the function is AS, AC and MT-safe like envz_strip.
I assume Alex and Carlos cannot review this since they have been
tainted by the original patch (I haven't even tried to look for a link
to it since I don't want to be tainted) so someone else will have to
review this. If there are no reviewers till the end of the week, I
will commit this since I believe there is a chance that there are no
other reviewers who haven't read that thread.
* manual/string.texi (Envz Functions): Add envz_remove.
The manual gives "an example showing how to handle failure to open a
file correctly." The example function, open_sesame, uses the
newly-introduced strerror function and errno and
program_invocation_short_name variables. It fails to specify GNU
extensions, however, so attempts to use it in the following way:
int main (void) {open_sesame ("badname");}
fail during compilation with "error: ‘program_invocation_short_name’
undeclared", indicating the example is incomplete. The presence of
"#include"s suggest everything neccesary for the function to work should
be present. For completeness, the example is lacking the following line:
#define _GNU_SOURCE
as the declarations of program_invocation_*name in errno.h are wrapped
in an "#ifdef __USE_GNU" conditional.
The documentation of the variables is also expanded, adding that their
definition lies in errno.h and noting specifically they are GNU
extensions.
This patch refines the math.texi documentation of the goals for when
libm function raise the inexact and underflow exceptions. The
previous text was problematic in some cases around the underflow
threshold.
* Strictly, it would have meant that if the mathematical result of pow
was very slightly below DBL_MIN, for example, it was required to
raise the underflow exception; although normally a few ulps error
would be OK, if that error meant the computed value was slightly
above DBL_MIN it would fail the previously described underflow
exception goal.
* Similarly, strict IEEE semantics would imply that sin (DBL_MIN), in
round-to-nearest mode, underflows on before-rounding but not
after-rounding architectures, while returning DBL_MIN; the previous
wording would have required an underflow exception, so preventing
checks for a result with absolute value below DBL_MIN from being
sufficient checks to determine whether the exception is required.
(Under the previous wording, checks for a result with absolute value
<= DBL_MIN wouldn't have been sufficient either, because in
FE_TOWARDZERO mode a result of DBL_MIN definitely does not result
from an underflowing infinite-precision result.)
* The previous wording about rounding infinite-precision values could
be taken to mean all exceptions including "inexact" must be
consistent with some such value. That would mean that a result of
DBL_MIN in FE_UPWARD mode with "inexact" raised must also have
"underflow" raised on before-rounding architectures. Again, that
would cause problems for computing a result (possibly with spurious
"inexact" exceptions) and then using a rounding-mode-independent
test for results with absolute value below DBL_MIN to determine
whether an underflow exception must be forced in case the underflows
from intermediate computations happened to be exact.
By refining the documentation, this patch avoids stating goals for
accuracy close to the underflow threshold that were stricter than
applied anywhere else, and allows the implementation strategy of:
compute a result within a few ulps, taking care to avoid underflows in
intermediate computations, then force an underflow exception if that
result was subnormal. Only fully-defined functions such as fma need
to take greater care about the exact underflow threshold (including
its dependence on whether the architecture is before-rounding or
after-rounding, and on the rounding mode on after-rounding
architectures).
(If the rounding mode is changed as part of the computation, it's
still necessary to ensure that not just intermediate computations, but
the final computation of the result to be returned, do not raise
underflow if that result is the least normal value and underflow would
be inconsistent with the original rounding mode. Since such code can
readily discard exceptions as part of saving and restoring the
rounding mode - SET_RESTORE_ROUND_NOEX etc. - I don't think that
should be a problem in practice.)
* manual/math.texi (Errors in Math Functions): Clarify goals
regarding inexact and underflow exceptions.
The tv_sec is of type time_t in both struct timeval and struct timespec.
This matches the implementation and also the relevant standard (checked
C11 for timespec and opengroup for timeval).
Update all translations.
Update contributions in the manual.
Update installation notes with information about newest working tools.
Reconfigure using exactly autoconf 2.69.
Regenerate INSTALL.
The merge of the latest gettext code introduced changes to the yacc
parser source that are incompatible with versions of bison older
than 2.7. Add a configure check for the appropriate versions and
document the requirement in INSTALL.
ChangeLog:
2014-12-22 Will Newton <will.newton@linaro.org>
* manual/install.texi: Document that we require bison 2.7
or above.
* INSTALL: Regenerate.
* configure.ac: Use AC_CHECK_PROG_VER instead of
AC_PATH_PROG when checking for bison and check for
version 2.7 or above.
* configure: Regenerate.
C99, C11, POSIX, and the glibc implementation do guarantee that the
pointers passed to the qsort comparison function lie within the array.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
It seems we require texinfo 4.7 for the --plaintext option, so
document that and check for the correct version in configure.
ChangeLog:
2014-12-15 Will Newton <will.newton@linaro.org>
* manual/install.texi: Bump required version of texinfo
to 4.7 from 4.5.
* INSTALL: Regenerated.
* configure.ac: Check for makeinfo version 4.7 and above.
* configure: Regenerated.
Under certain conditions on the size of the array and its items,
qsort() may fall back to an in-place quicksort if it cannot allocate
memory for a temporary array with malloc(). This algorithm is not a
stable sort even if the comparison function is written in the
described manner.
Fixes#10672.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
As discussed starting at
<https://sourceware.org/ml/libc-alpha/2014-11/msg00323.html>, this
patch makes the glibc build use -Werror by default to avoid
accidentally adding new warnings to the build. The configure option
--disable-werror can be used to disable this.
-Wno-error=undef is temporarily used because the build isn't clean
regarding -Wundef warnings. The idea is that once the remaining
-Wundef warnings have been cleaned up (in at least one configuration),
-Wno-error=undef will be removed.
I get a clean build and test on x86_64 (GCC 4.9 branch) with this
patch. The expectation is that this may well break the build for some
other configurations, and people seeing such breakage should make
appropriate fixes to fix or suppress the warnings for their
configurations. In some cases that may involve using pragmas as the
right fix (I think that will be right for the -Wno-inline issue for
MIPS I referred to in
<https://sourceware.org/ml/libc-alpha/2012-11/msg00798.html>, for
example), in some cases -Wno-error in sysdeps makefiles (__restore_rt
in MIPS sigaction, for example), in some cases substantive fixes for
the warnings.
Note that if, with a view to listing all the warnings then fixing them
all, you just look for "warning:" in output from building and testing
with --disable-werror, you'll see lots of warnings from the linker
about functions such as tmpnam. Those warnings can be ignored - only
compiler warnings are relevant to -Werror, not linker warnings.
* configure.ac (--disable-werror): New configure option.
(enable_werror): New AC_SUBST.
* configure: Regenerated.
* config.make.in (enable-werror): New variable.
* Makeconfig [$(enable-werror) = yes] (+gccwarn): Add -Werror
-Wno-error=undef.
(+gccwarn-c): Do not use -Werror=implicit-function-declaration.
* manual/install.texi (Configuring and compiling): Document
--disable-werror.
* INSTALL: Regenerated.
* debug/Makefile (CFLAGS-tst-chk1.c): Add -Wno-error.
(CFLAGS-tst-chk2.c): Likewise.
(CFLAGS-tst-chk3.c): Likewise.
(CFLAGS-tst-chk4.cc): Likewise.
(CFLAGS-tst-chk5.cc): Likewise.
(CFLAGS-tst-chk6.cc): Likewise.
(CFLAGS-tst-lfschk1.c): Likewise.
(CFLAGS-tst-lfschk2.c): Likewise.
(CFLAGS-tst-lfschk3.c): Likewise.
(CFLAGS-tst-lfschk4.cc): Likewise.
(CFLAGS-tst-lfschk5.cc): Likewise.
(CFLAGS-tst-lfschk6.cc): Likewise.
