Clang's gnu99 mode is not quite the same as GCC's. It will complain
about redefined typedefs being a C11 feature, while GCC does not
complain and allows them in gnu99 mode.
Reviewed-by: NFabiano Fidêncio <fidencio@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

When adding the -std=gnu99 flag, we set $wantwarn instead
of appending to it. This meant all the compiler warnings
were accidentally discarded.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

We previously got -std=gnu99 secretly enabled as a side-effect
of requesting the 'stdarg' gnulib module. We rely on some
extensions from c99/gnu99 and while RHEL-7 supports this, it
still defaults to gnu89.  RHEL-7 also supports some newer
standards but declares them experimental/incomplete, so sticking
with gnu99 is best bet for now & matches historical usage.
Reviewed-by: NFabiano Fidêncio <fidencio@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

The previous bump to 4.4 was done in:

  commit 24241c23
  Author: Daniel P. Berrange <berrange@redhat.com>
  Date:   Wed Jul 5 10:35:32 2017 +0100

    Require use of GCC 4.4 or CLang compilers

with 4.4 picked due to RHEL-6. Since we dropped RHEL-6, the
next oldest distro is RHEL-7 (4.8.5), and thus we pick 4.8
as the new min.
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

As a general rule any time we switch() on something that is an enum, we
want to have a case for every enum constant. The -Wswitch warning will
report any switch where we've violated this rule, except if that switch
has a default case.

Unfortunately it is reasonable to want to list all enum constants *and*
also have a default case. To get a warning in that scenario requires
that we turn on -Wswitch-enum.

In a few cases where we explicitly don't want to list all enum cases, we
can discard the enum type checking by casting the value to a plain int.
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

The -Wextra flag bundle gained a new warning -Wcast-function-type.
This complains if you cast between two function prototypes where
the number of parameters or their data types are not compatible.
Unfortunately we need such "bad" function casts for our event
callbacks. It is possible to silence the warning by first casting
to the generic "void (*)(void)" function prototype, but that is
rather ugly to add throughout libvirt code.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

After the latest CPU additions, the build fails with clang:
cputest.c:905:1: error: stack frame size of 26136 bytes
  in function 'mymain' [-Werror,-Wframe-larger-than=]

Raise the relaxed limit which is used for tests.

After b4f7793c, qemuxml2xmltest has apparently become big enough
to trigger a compilation error when using --enable-test-coverage on
aarch64:

    CC       qemuxml2xmltest.o
  qemuxml2xmltest.c: In function 'mymain':
  qemuxml2xmltest.c:1216:1: error: const/copy propagation disabled: 4361 basic blocks and 99285 registers [-Werror=disabled-optimization]
   }
   ^
  qemuxml2xmltest.c:1216:1: error: PRE disabled: 4361 basic blocks and 99285 registers [-Werror=disabled-optimization]
  qemuxml2xmltest.c:1216:1: error: const/copy propagation disabled: 4361 basic blocks and 99285 registers [-Werror=disabled-optimization]
  qemuxml2xmltest.c:1216:1: error: const/copy propagation disabled: 4361 basic blocks and 99285 registers [-Werror=disabled-optimization]

However, as the GCC documentation states, this warning is not really
caused by issues in our code, so it makes sense to disable it.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NDaniel P. Berrange <berrange@redhat.com>

3 out of 4 uses of gl_WARN_ADD() were incorrectly adding "" around
the argument, which in turn resulted in the argument being used
unquoted (configure had gl_positive=""-fstack-protector-all"",
rather than the intended gl_positive="-fstack-protector-all").
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

When building libvirt with clang we get bogus warnings about
'double' being promoted to 'long double' when calling isnan().

  https://bugzilla.redhat.com/show_bug.cgi?id=1472437

Detect this broken isnan() / compiler combination and disable
the -Wdouble-promotion flag.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

GCC 7.1 introduces a new -Wformat-truncation warning
flag that reports if it thinks the maximum possible
size of the formatted output will exceed the provided
fixed buffer. This is enabled automatically by the
-Wformat warning flag. There are quite a few places
hit by this in libvirt which need rewriting. This is
non-trivial work in some places, so temporarily
disable the new warning until those fixes can be
implemented.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Depending on the platform/architecture, a number of conditionals
in libvirt code expand the same on both branches. This is expected
behaviour and harmless, so disable the warning to avoid creating
unexpected build failures

Two examples, mingw32:

../../src/util/vircommand.c: In function 'virCommandWait':
../../src/util/vircommand.c:2562:51: error: this condition has identical branches [-Werror=duplicated-branches]
             *exitstatus = cmd->rawStatus ? status : WEXITSTATUS(status);
                                                   ^
and gcc7.1

In file included from util/virobject.c:28:0:
util/virobject.c: In function 'virClassNew':
util/viratomic.h:176:46: error: this condition has identical branches [-Werror=duplicated-branches]
            (void)(0 ? *(atomic) ^ *(atomic) : 0);                      \
                                             ^
util/virobject.c:144:20: note: in expansion of macro 'virAtomicIntInc'
    klass->magic = virAtomicIntInc(&magicCounter);
                   ^~~~~~~~~~~~~~~
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Introduce STRICT_FRAME_LIMIT_CFLAGS that will be used for
production code and RELAXED_FRAME_LIMIT_CFLAGS for tests.

Raising the limit for tests allows building them with clang
with optimizations disabled.

Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

fdstream.c: In function 'virFDStreamWrite':
fdstream.c:390:29: error: logical 'or' of equal expressions [-Werror=logical-op]
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
                            ^~

Fedora rawhide now uses gcc 6.0 and there is a bug with -Wlogical-op
producing false warnings.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602

Use GCC pragma push/pop and ignore -Wlogical-op for GCC that supports
push/pop pragma and also has this bug.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

Time to update to new gnulib before a release.

gcc 5.1 introduced a new -Wformat-signedness, and new gnulib now
turns it on by default.  However, it is still rather lame at the
moment, because it warns for enums, even though there is no way
to control the signeness of an enum which does not use any members
that are negative or larger than INT_MAX, and even though such an
enum would always print the same for both %d and %u:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66249

In file included from ../../src/util/virarch.c:26:0:
../../src/util/virarch.c: In function 'virArchFromHost':
../../src/util/virarch.c:180:15: error: format '%d' expects argument of type 'int', but argument 9 has type 'unsigned int' [-Werror=format=]
     VIR_DEBUG("Mapped %s to %d (%s)",

So this patch turns off the new warning as part of enabling all
other new gcc 5.1 warnings that gnulib now enables.

* .gnulib: Update to latest, in part for gcc 5.1 interaction.
* m4/virt-compile-warnings.m4: Ignore -Wformat-signedness, for now.
Signed-off-by: NEric Blake <eblake@redhat.com>

Many GCC versions don't understand -Wno-suggest-attribute=format
so the pragma must only be used when supported

Try -fstack-protector-strong first on Linux. If that fails,
fall back to -fstack-protector-all.

This option only makes sense for -fstack-protector.
With -fstack-protector-all or -fstack-protector-strong,
functions are protected regardless of buffer size.

https://bugzilla.redhat.com/show_bug.cgi?id=1105456

These warnings have already been added to $dontwarn.

I'm using gcc-4.8.2-7.fc21.aarch64 which does not appear to support
this option.

The python binding now lives in

  http://libvirt.org/git/?p=libvirt-python.git

that repo also provides an RPM which is upgrade compatible
with the old libvirt-python sub-RPM.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Since we're about to freeze, it's time to pick up the latest
upstream gnulib.  Among other changes, gnulib now guarantees the
use of some -f flags that we were previously manually adding.

* .gnulib: Update to latest, in part for warning improvements.
* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Drop
flags that are now guaranteed by gnulib.
* bootstrap: Resync to gnulib.
Signed-off-by: NEric Blake <eblake@redhat.com>

Rather than inlining gl_WARN_ADD loads of time, we can shave about
17k size off of the configure script by delaying it to a cleanup
shell loop.

* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Track a
list of things to check, rather than inlining multiple checks.
Signed-off-by: NEric Blake <eblake@redhat.com>

https://bugzilla.redhat.com/show_bug.cgi?id=994589 complained that
even when using a cross-compiler not named 'gcc', the configure
output confusingly referred to gcc.

* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Use a
more generic statement in configure output.
Signed-off-by: NEric Blake <eblake@redhat.com>

Partially revert cdd703f4's revert of c1634100, as linking with clang
with --param=ssp-buffer-size=4 still fails with:
"argument unused during compilation".

The latest mingw headers on Fedora 19 fail to build with gnulib
without an update.

Meanwhile, now that upstream gnulib has better handling of -W
probing for clang, we can drop some of our own solutions in
favor of upstream; thus this reverts commit c1634100, "Correctly
detect warning flags with clang".

* .gnulib: Update to latest, for mingw and clang.
Signed-off-by: NEric Blake <eblake@redhat.com>

FreeBSD ships an old gcc 4.2.1 which generates
bogus code, e.g. getsockopt() call returns
struct xucred with bogus values, which doesn't even
allow to connect to libvirtd:

error: Failed to find group record for gid '1284660778': No error: 0

So roll back to just -fstack-protector on FreeBSD.

Automake already passes all CFLAGS to the linker too, so it
is not necessary to set WARN_LDFLAGS in addition to the
WARN_CFLAGS variable.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Clang will happily claim to support any warning flags
unless the -Werror and -Wunknown-warning-option flags
are set. Thus we need to make sure these are set when
testing for clags.

We must also set the clang specific warning flags
-Wno-unused-command-line-argument to avoid a warning
from the ssp-buffer-size flag when linking .o files.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The virt-compile-warnings.m4 file would do an explicit
check for whether the compile could use the 'diagnostic'
pragma push/pop feature. The src/internal.h file would
then only enable it for GCC >= 4.6

This breaks with clang which supports the pragma but
does not claim GCC 4.6 compat. Export a variable from
the m4 check to the header file so they are consistent.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

There are a number of places which generate cast alignment
warnings, which are difficult or impossible to address. Use
pragmas to disable the warnings in these few places

conf/nwfilter_conf.c: In function 'virNWFilterRuleDetailsParse':
conf/nwfilter_conf.c:1806:16: warning: cast increases required alignment of target type [-Wcast-align]
         item = (nwItemDesc *)((char *)nwf + att[idx].dataIdx);
conf/nwfilter_conf.c: In function 'virNWFilterRuleDefDetailsFormat':
conf/nwfilter_conf.c:3238:16: warning: cast increases required alignment of target type [-Wcast-align]
         item = (nwItemDesc *)((char *)def + att[i].dataIdx);

storage/storage_backend_mpath.c: In function 'virStorageBackendCreateVols':
storage/storage_backend_mpath.c:247:17: warning: cast increases required alignment of target type [-Wcast-align]
         names = (struct dm_names *)(((char *)names) + next);

nwfilter/nwfilter_dhcpsnoop.c: In function 'virNWFilterSnoopDHCPDecode':
nwfilter/nwfilter_dhcpsnoop.c:994:15: warning: cast increases required alignment of target type [-Wcast-align]
         pip = (struct iphdr *) pep->eh_data;
nwfilter/nwfilter_dhcpsnoop.c:1004:11: warning: cast increases required alignment of target type [-Wcast-align]
     pup = (struct udphdr *) ((char *) pip + (pip->ihl << 2));

nwfilter/nwfilter_learnipaddr.c: In function 'procDHCPOpts':
nwfilter/nwfilter_learnipaddr.c:327:33: warning: cast increases required alignment of target type [-Wcast-align]
                 uint32_t *tmp = (uint32_t *)&dhcpopt->value;
nwfilter/nwfilter_learnipaddr.c: In function 'learnIPAddressThread':
nwfilter/nwfilter_learnipaddr.c:501:43: warning: cast increases required alignment of target type [-Wcast-align]
                     struct iphdr *iphdr = (struct iphdr*)(packet +
nwfilter/nwfilter_learnipaddr.c:538:43: warning: cast increases required alignment of target type [-Wcast-align]
                     struct iphdr *iphdr = (struct iphdr*)(packet +
nwfilter/nwfilter_learnipaddr.c:544:48: warning: cast increases required alignment of target type [-Wcast-align]
                         struct udphdr *udphdr= (struct udphdr *)
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Commit 8b8fcdea introduced a check for broken gcc -Wlogical-op,
but did not guard the check against non-gcc compilers, which might
lead to spurious failures when another compiler encounters an
unknown pragma.  Additionally, all of our compiler warning logic
should belong in a single file, and use cache variables to allow
overriding the decision at configure time if necessary.

* configure.ac (BROKEN_GCC_WLOGICALOP): Move...
* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): ...here,
and update to modern autoconf idioms.

Based on this coreutils bug report, since coreutils copied what
libvirt had done:
https://lists.gnu.org/archive/html/bug-coreutils/2012-10/msg00121.html

* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Allow
for user to pre-define _FORTIFY_SOURCE.

Commit c579d6b3 added a sledgehammer to silence spurious warnings from
gcc 4.2, but in the process, it also silenced useful warnings from
gcc 4.3 through 4.5.  As a result, a bug slipped in to commit 0caccb58.

Tested with FreeBSD (gcc 4.2.1), RHEL 6.3 (gcc 4.4), and F17 (gcc 4.7.2),
where the former didn't trip on spurious warnings, and where the latter
two detected a revert of 2b804cfa.

* m4/virt-compile-warnings.m4 (-Wno-format): Probe for the actual
spurious message, to once again allow gcc 4.4 to use -Wformat.

On RHEL 6.2, gcc 4.4.6 complains:
cc1: warning: command line option "-Wenum-compare" is valid for C++/ObjC++ but not for C
which in turn breaks a -Werror build.

Meanwhile, in Fedora 17, gcc 4.7.0, -Wenum-compare has been enhanced
to also work on C, but at the same time, it is documented that -Wall
now implicitly includes -Wenum-compare.

Therefore, it is sufficient to remove explicit checks for this option,
avoiding the warning from older gcc while still getting the
compile-time safety from newer gcc.

* m4/virt-compile-warnings.m4 (-Wenum-compare): Omit explicit check.

OpenBSD ships with gcc 4.2.1, which annoyingly treats all format
strings as though they were also attribute((nonnull)).  The two
concepts are orthogonal, though, as evidenced by the number of
spurious warnings it generates on uses where we know that
virReportError specifically handles NULL instead of a format
string; worse, since we now force -Werror on git builds, it
prevents development builds on OpenBSD.

I hate to do this, as it disables ALL format checking on older
gcc, and therefore misses out on some useful checks (code that
happened to compile on Linux may still have type mismatches
when compiled on other platforms, as evidenced by the number
of times I have fixed formatting mismatches for uid_t as found
by warnings on Cygwin), but I don't see any other way to keep
-Werror alive and still compile on OpenBSD.

A more invasive change would be to make virReportError() mark
its format attribute as nonnull, and fix (a lot of) fallout;
we may end up doing that anyways as part of danpb's error
refactoring improvements, but not today.

* src/internal.h (ATTRIBUTE_FMT_PRINTF): Use preferred spellings.
* m4/virt-compile-warnings.m4 (-Wformat): Disable on older gcc.

A previous patch (c606671a) pulled in a newer version of
stat-time.h from gnulib, which causes some warnings in older gcc:

  CC     libvirt_driver_storage_la-storage_backend.lo
cc1: warnings being treated as errors
In file included from ../../src/storage/storage_backend.c:59:
../../gnulib/lib/stat-time.h:55: error: no previous prototype for 'get_stat_atime_ns' [-Wmissing-prototypes]

Upstream gnulib argues that these warnings are stupid (and I agree;
see <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54113>), and has
used a modern gcc feature (#pragma GCC diagnostic push) to avoid the
warning.  But we still aim to compile on RHEL 6.3, with gcc 4.4.6
(not to mention even older platforms like RHEL 5), and therefore
the warning trips up our default of development with -Werror.

It took me a while to figure out how to make our set of warnings
smaller on older gcc without losing the benefit of the warnings
when using newer gcc (such as the one on Fedora 17), but this
should do the trick.

* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Avoid
warnings that gnulib can't silence on older gcc.

The access, birth, modification and change times are added to
storage volumes and corresponding xml representations.  This
shows up in the XML in this format:

<timestamps>
  <atime>1341933637.027319099</atime>
  <mtime>1341933637.027319099</mtime>
</timestamps>
Signed-off-by: NEric Blake <eblake@redhat.com>