[PATCH v2 6/6] build: limit scope of packed member warning disabling

[Bruce Richardson]

The flag '-Wno-address-of-packed-member' is a global warning flag in
DPDK. Rather than disabling this warning globally, it is better to just
have it enabled for components that may need it. This patch limits the
scope of it in the following ways:

* limit the use of the flag to the drivers subfolder only - all libs and
  apps should be buildable without the warning.
* exception is made for the vhost library and the ipsec-secgw example
  for now, as making them buildable with the warning enabled is more
  complicated. This exception can hopefully be removed in future.

Limiting the scope further within the drivers directory is also left for
future consideration. However, since HW drivers often have to use packed
structures to align with hardware-implemented data layouts, it may be
more practical to keep the warning disabled in the longer term.

Signed-off-by: Bruce Richardson <bruce.richard...@intel.com>
Acked-by: Stephen Hemminger <step...@networkplumber.org>
Acked-by: Morten Brørup <m...@smartsharesystems.com>
---
 config/meson.build               | 1 -
 drivers/meson.build              | 9 ++++++---
 examples/ipsec-secgw/meson.build | 6 ++++++
 lib/vhost/meson.build            | 5 ++++-
 4 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/config/meson.build b/config/meson.build
index 8dae811378..5095d2fbcb 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -325,7 +325,6 @@ warning_flags = [
         '-Wwrite-strings',
 
         # globally disabled warnings
-        '-Wno-address-of-packed-member',
         '-Wno-packed-not-aligned',
         '-Wno-missing-field-initializers',
 ]
diff --git a/drivers/meson.build b/drivers/meson.build
index 5270160c56..4a27f197a8 100644
--- a/drivers/meson.build
+++ b/drivers/meson.build
@@ -59,9 +59,12 @@ default_cflags = machine_args
 default_cflags += ['-DALLOW_EXPERIMENTAL_API']
 default_cflags += ['-DALLOW_INTERNAL_API']
 
-if cc.has_argument('-Wno-format-truncation')
-    default_cflags += '-Wno-format-truncation'
-endif
+warning_disable_cflags = ['-Wno-format-truncation', 
'-Wno-address-of-packed-member']
+foreach cflag:warning_disable_cflags
+    if cc.has_argument(cflag)
+        default_cflags += cflag
+    endif
+endforeach
 
 dpdk_drivers_build_dir = meson.current_build_dir()
 
diff --git a/examples/ipsec-secgw/meson.build b/examples/ipsec-secgw/meson.build
index ccdaef1c4d..023d9cf039 100644
--- a/examples/ipsec-secgw/meson.build
+++ b/examples/ipsec-secgw/meson.build
@@ -23,3 +23,9 @@ sources = files(
         'sp4.c',
         'sp6.c',
 )
+app_cflags = ['-Wno-address-of-packed-member']
+foreach flag:app_cflags
+    if cc.has_argument(flag)
+        cflags += flag
+    endif
+endforeach
diff --git a/lib/vhost/meson.build b/lib/vhost/meson.build
index 41b622a9be..51bcf17244 100644
--- a/lib/vhost/meson.build
+++ b/lib/vhost/meson.build
@@ -16,7 +16,10 @@ elif (toolchain == 'icc' and 
cc.version().version_compare('>=16.0.0'))
     cflags += '-DVHOST_ICC_UNROLL_PRAGMA'
 endif
 dpdk_conf.set('RTE_LIBRTE_VHOST_POSTCOPY', 
cc.has_header('linux/userfaultfd.h'))
-cflags += '-fno-strict-aliasing'
+cflags += [
+        '-fno-strict-aliasing',
+        '-Wno-address-of-packed-member',
+]
 
 sources = files(
         'fd_man.c',
-- 
2.43.0