With gcc 4.3.4 I'm seeing the following warning failure

cc1: warnings being treated as errors
cc1: error: -funit-at-a-time is required for inlining of functions
that are only called once [-Wdisabled-optimization]

Add -funit-at-a-time to WARN_CFLAGS.

The GCC Win32 compiler will claim to support -fstack-protector,
but if it actually gets triggered by a suitable code pattern,
linking will fail. Other non-Linux OS likely suffer the same
way with gcc.

* m4/virt-compile-warnings.m4: Only use stack protector when
  the build target is Linux.

A couple of functions were declared using the old style foo()
for no-parameters, instead of foo(void)

* src/xen/xen_hypervisor.c, tests/testutils.c: Replace () with (void)
  in some function declarations
* m4/virt-compile-warnings.m4: Enable -Wold-style-definition

* src/internal.h: Define a ATTRIBUTE_NO_RETURN annotation
* src/lxc/lxc_container.c: Annotate lxcContainerDummyChild
  with ATTRIBUTE_NO_RETURN
* tests/eventtest.c: Mark async thread as ATTRIBUTE_NO_RETURN
* m4/virt-compile-warnings.m4: Enable -Wmissing-noreturn

Add a couple of missing ATTRIBUTE_FMT_PRINTF annotations

* tools/virsh.c, tests/testutils.c: Add printf format attribute
* m4/virt-compile-warnings.m4: Enable -Wmissing-format-attribute

Split the bit acinclude.m4 file into smaller pieces named
as m4/virt-XXXXX.m4

* .gitignore: Ignore gettext related files
* acinclude.m4: Delete
* m4/virt-compile-warnings.m4: Checks for GCC compiler flags
* m4/virt-pkgconfig-back-compat.m4: Backcompat check for
  pkgconfig program

Remove custom code for checking compiler warnings, using
gl_WARN_ADD instead. Don't list all flags ourselves, use
gnulib's gl_MANYWARN_ALL_GCC to get all possible GCC flags,
then turn off the ones we don't want yet.

* acinclude.m4: Rewrite to use gl_WARN_ADD and gl_MANYWARN_ALL_GCC
* bootstrap.conf: Add warnings & manywarnings
* configure.ac: Switch to gl_WARN_ADD
* m4/compiler-flags.m4: Obsoleted by gl_WARN_ADD

Even with -Wuninitialized (which is part of autobuild.sh
--enable-compile-warnings=error), gcc does NOT catch this
use of an uninitialized variable:

{
  if (cond)
    goto error;
  int a = 1;
error:
  printf("%d", a);
}

which prints 0 (supposing the stack started life wiped) if
cond was true.  Clang will catch it, but we don't use clang
as often.  Using gcc -Wjump-misses-init catches it, but also
gives false positives:

{
  if (cond)
    goto error;
  int a = 1;
  return a;
error:
  return 0;
}

Here, a was never used in the scope of the error block, so
declaring it after goto is technically fine (and clang agrees).
However, given that our HACKING already documents a preference
to C89 decl-before-statement, the false positive warning is
enough of a prod to comply with HACKING.

[Personally, I'd _really_ rather use C99 decl-after-statement
to minimize scope, but until gcc can efficiently and reliably
catch scoping and uninitialized usage bugs, I'll settle with
the compromise of enforcing a coding standard that happens to
reject false positives if it can also detect real bugs.]

* acinclude.m4 (LIBVIRT_COMPILE_WARNINGS): Add -Wjump-misses-init.
* src/util/util.c (__virExec): Adjust offenders.
* src/conf/domain_conf.c (virDomainTimerDefParseXML): Likewise.
* src/remote/remote_driver.c (doRemoteOpen): Likewise.
* src/phyp/phyp_driver.c (phypGetLparNAME, phypGetLparProfile)
(phypGetVIOSFreeSCSIAdapter, phypVolumeGetKey)
(phypGetStoragePoolDevice)
(phypVolumeGetPhysicalVolumeByStoragePool)
(phypVolumeGetPath): Likewise.
* src/vbox/vbox_tmpl.c (vboxNetworkUndefineDestroy)
(vboxNetworkCreate, vboxNetworkDumpXML)
(vboxNetworkDefineCreateXML): Likewise.
* src/xenapi/xenapi_driver.c (getCapsObject)
(xenapiDomainDumpXML): Likewise.
* src/xenapi/xenapi_utils.c (createVMRecordFromXml): Likewise.
* src/security/security_selinux.c (SELinuxGenNewContext):
Likewise.
* src/qemu/qemu_command.c (qemuBuildCommandLine): Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeEjectableMedia):
Likewise.
* src/qemu/qemu_process.c (qemuProcessWaitForMonitor): Likewise.
* src/qemu/qemu_monitor_text.c (qemuMonitorTextGetPtyPaths):
Likewise.
* src/qemu/qemu_driver.c (qemudDomainShutdown)
(qemudDomainBlockStats, qemudDomainMemoryPeek): Likewise.
* src/storage/storage_backend_iscsi.c
(virStorageBackendCreateIfaceIQN): Likewise.
* src/node_device/node_device_udev.c (udevProcessPCI): Likewise.

This would have detected the bug in commit 38ad33931 (Aug 09), which
we missed until commit f828ca35 (Jul 10); over 11 months later.

However, on Fedora 13, it also triggers LOTS of warnings from
the libcurl-devel header for two files:

esx/esx_vi.c: In function 'esxVI_CURL_Perform':
esx/esx_vi.c:232: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
esx/esx_vi.c:232: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
esx/esx_vi.c:232: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
...
xenapi/xenapi_driver.c: In function 'call_func':
xenapi/xenapi_driver.c:1872: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
xenapi/xenapi_driver.c:1872: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
xenapi/xenapi_driver.c:1872: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op]
...

libcurl allows to disable the type-checking code that triggers those
warnings, along with the reduction in type-safety of calls to some
libcurl functions. I figure this is worth the improved compiler
checking throughout the rest of libvirt.

* acinclude.m4 (--enable-compile-warnings=error): Add -Wlogical-op.
* configure.ac: Add -DCURL_DISABLE_TYPECHECK to LIBCURL_CFLAGS to
avoid compilation warning.

Suggested by Daniel P. Berrange.
Tweaked by Matthias Bolte.

Matthias noted that the line:
virt_aa_helper_LDFLAGS = $(WARN_CFLAGS)
looks inconsistent, so I did an audit.

Currently, the set of compiler warning flags passed to gcc as $CC are
equally permitted as the set of linker flags passed to gcc as $LD, so
there was no problem with that usage.  But if we ever get in a
situation where $CC and $LD treat particular flags differently, using
the right variable form will make it easier.

In the process, I spotted a couple of typos that were omitting useful
flags, as well as specifying a -l under the wrong variable.

* acinclude.m4 (LIBVIRT_COMPILE_WARNINGS): Define WARN_LDFLAGS as
an alias for WARN_CFLAGS.
* tools/Makefile.am (virsh_LDFLAGS): Use more canonical spelling.
* proxy/Makefile.am (libvirt_proxy_LDFLAGS): Likewise. Move
library...
(libvirt_proxy_LDADD): ...here.
* src/Makefile.am (virt_aa_helper_LDFLAGS): Use more canonical
spelling of WARN_LDFLAGS.
(libvirt_parthelper_LDFLAGS, libvirt_lxc_LDFLAGS): Likewise.  Use
correct spelling of COVERAGE_LDFLAGS.
Reported by Matthias Bolte.

* acinclude.m4 (LIBVIRT_COMPILE_WARNINGS): Add
-fdiagnostics-show-option.

by running this command:
git ls-files -z | xargs -0 perl -pi -0777 -e 's/\n\n+$/\n/'
This is in preparation for a more strict make syntax-check
rule that will detect trailing blank lines.

        Avoid risk of format string abuse (also avoids gcc warnings).
        * src/util.c (ReportError): Use a literal "%s" format string.
        * src/remote_internal.c (server_error): Likewise.
        * src/qemu_conf.c (qemudReportError): Likewise.
        * acinclude.m4: Add -Wformat -Wformat-security to default
          list of warning flags, to warn about errors such as the
          above.

        * acinclude.m4, configure.in: ./configure option
          --disable-stack-protector.
        * src/gnutls_1_0_compat.h: Compatibility with GnuTLS 1.0.
        * src/bridge.c: If no bridge ioctls, give an error at runtime.

  user specified CFLAGS
Daniel

        * acinclude.m4: add LIBVIRT_COMPILE_WARNINGS, copied from
        GNOME but with a few more flags we'd been using.

        * configure.in: use that instead of setting CFLAGS
        directly.

        * proxy/Makefile.am, python/Makefile.am, qemud/Makefile.am,
          src/Makefile.am, tests/Makefile.am: use $(WARN_CFLAGS)