[PATCH] cryptodev: fix stringop-overflow build failure with gcc 10

[christian.ehrhardt@canonical.com]

From: Christian Ehrhardt <christian.ehrhardt@canonical.com>

19.11 LTS releases started to fail to build in some newer releases
due to newer gcc-10 compilers available. Those are mostly false
positives [1][2] and to some extend covered by the already present
backports of "4990929c60 eal/ppc: ignore GCC 10 stringop-overflow
warnings" and "df17bcb43b eal/x86: ignore gcc 10 stringop-overflow
warnings".

But the combination of 19.11 and gcc 10.3.0 and LTO this can still
exposes the issue.

[  549s] In function ‘_mm_storeu_si128’,
[  549s]     inlined from ‘rte_memcpy_generic’
  at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:508:2,
[  549s]     inlined from ‘rte_cryptodev_sym_session_set_user_data’
  at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:882:10:
[  549s] /usr/lib/gcc/x86_64-linux-gnu/10/include/emmintrin.h:727:8:
  error: writing 16 bytes into a region of size 0
  [-Werror=stringop-overflow=]
[  549s]   727 |   *__P = __B;
[  549s]       |        ^
[  549s] ../lib/librte_cryptodev/rte_cryptodev.c:
  In function ‘rte_cryptodev_sym_session_set_user_data’:
[  549s] ../lib/librte_cryptodev/rte_cryptodev.h:984:4: note:
  at offset 0 to object ‘sess_data’ with size 0 declared here
[  549s]   984 |  } sess_data[0];
[  549s]       |    ^

The problem is that in this combination only at link time (LTO)
the compiler will (false-)detect the problematic size of the target
structure and break. To make things worse [3] fixed this problem
for the same issue at actual build time, but the pragma has no
effect at link time nor are any werror settings passed to the
linker.

For affected compilers set -Wno-stringop-overflow globally for
the linker stage to avoid this breaking the build in any place.

Buzilla ID: 908

[1]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94335
[2]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92955
[3]: https://github.com/DPDK/dpdk/commit/b5b3ea803e47

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
---
 config/meson.build | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/config/meson.build b/config/meson.build
index 4007b8f37c..25dec320ba 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -143,6 +143,14 @@ if numa_dep.found() and cc.has_header('numaif.h')
 	dpdk_extra_ldflags += '-lnuma'
 endif
 
+# Some false positives can trigger at LTO stage, so this warning needs to be
+# disabled on the linker as well for gcc 10.
+# Fixed in gcc-11 and not present <gcc-10
+# https://bugs.dpdk.org/show_bug.cgi?id=908
+if cc.get_id() == 'gcc' and cc.version().version_compare('>=10.0') and cc.version().version_compare('<11.0')
+	add_project_link_arguments('-Wno-stringop-overflow', language: 'c')
+endif
+
 has_libfdt = 0
 fdt_dep = cc.find_library('libfdt', required: false)
 if fdt_dep.found() and cc.has_header('fdt.h')
-- 
2.34.1