[dpdk-dev] [PATCH] build: gcc 10 disable stringop-overflow warnings

[Kevin Traynor <ktraynor@redhat.com>]

stringop-overflow warns when it sees a possible overflow
in a string operation.

In the rte_memcpy functions different implementations are
used depending on the size. stringop-overflow is raised for
the paths in the function where it sees the static size of the
src could be overflowed.

However, in reality a correct size argument and in some cases
dynamic allocation would ensure that this does not happen.

Disable this warning at the top level as it is being raised on
several components.

For example, in the case below for key, the correct path will be
chosen in rte_memcpy_generic at runtime based on the size argument
but as some paths in the function could lead to a cast to 32 bytes
a warning is raised.

In function ‘_mm256_storeu_si256’,
inlined from ‘rte_memcpy_generic’
at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:315:2,
inlined from ‘iavf_configure_rss_key’
at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:869:10:

/usr/lib/gcc/x86_64-redhat-linux/10/include/avxintrin.h:928:8:
warning: writing 32 bytes into a region of size 1 [-Wstringop-overflow=]
  928 |   *__P = __A;
      |   ~~~~~^~~~~
In file included
from ../drivers/net/iavf/../../common/iavf/iavf_prototype.h:10,
from ../drivers/net/iavf/iavf.h:9,
from ../drivers/net/iavf/iavf_vchnl.c:22:

../drivers/net/iavf/iavf_vchnl.c:
In function ‘iavf_configure_rss_key’:

../drivers/net/iavf/../../common/iavf/virtchnl.h:508:5:
note: at offset 0 to object ‘key’ with size 1 declared here
  508 |  u8 key[1];         /* RSS hash key, packed bytes */
      |     ^~~

Bugzilla ID: 394
Bugzilla ID: 421

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
---
 config/meson.build           | 3 ++-
 mk/toolchain/gcc/rte.vars.mk | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/config/meson.build b/config/meson.build
index 58421342b..476a667a9 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -200,5 +200,6 @@ warning_flags = [
 	'-Wno-address-of-packed-member',
 	'-Wno-packed-not-aligned',
-	'-Wno-missing-field-initializers'
+	'-Wno-missing-field-initializers',
+	'-Wno-stringop-overflow'
 ]
 if not dpdk_conf.get('RTE_ARCH_64')
diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
index f19305e49..fe4b8c705 100644
--- a/mk/toolchain/gcc/rte.vars.mk
+++ b/mk/toolchain/gcc/rte.vars.mk
@@ -101,4 +101,7 @@ endif
 WERROR_FLAGS += -Wno-address-of-packed-member
 
+# disable stringop-overflow warnings
+WERROR_FLAGS += -Wno-stringop-overflow
+
 export CC AS AR LD OBJCOPY OBJDUMP STRIP READELF
 export TOOLCHAIN_CFLAGS TOOLCHAIN_LDFLAGS TOOLCHAIN_ASFLAGS
-- 
2.21.1