[dpdk-stable] [PATCH v3 2/3] common/mlx5: fix build with -fno-common

[Thomas Monjalon <thomas@monjalon.net>]

The variable storages of the same name are merged together
if compiled with -fcommon. This is the default.
This default behaviour allows to declare a variable in a header file
and share the variable in every .o binaries thanks to merge at link-time.

In the case of dlopen linking of the glue library, the pointer mlx5_glue
is referencing the glue functions struct and is set after calling dlopen.

If compiling with -fno-common (default in GCC 10), the variable
must be declared as extern to avoid multiple re-definitions.
In case the glue layer is split in glue library, the variable mlx5_glue
needs to have its own storage for the rest of the PMD.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/common/mlx5/mlx5_common.c | 3 +++
 drivers/common/mlx5/mlx5_glue.h   | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/common/mlx5/mlx5_common.c b/drivers/common/mlx5/mlx5_common.c
index d8c01a5d14..42610459f7 100644
--- a/drivers/common/mlx5/mlx5_common.c
+++ b/drivers/common/mlx5/mlx5_common.c
@@ -18,6 +18,9 @@
 
 int mlx5_common_logtype;
 
+#ifdef MLX5_GLUE
+const struct mlx5_glue *mlx5_glue;
+#endif
 
 /**
  * Get PCI information by sysfs device path.
diff --git a/drivers/common/mlx5/mlx5_glue.h b/drivers/common/mlx5/mlx5_glue.h
index 6238b43946..29678623e4 100644
--- a/drivers/common/mlx5/mlx5_glue.h
+++ b/drivers/common/mlx5/mlx5_glue.h
@@ -300,6 +300,6 @@ struct mlx5_glue {
 			 size_t event_resp_len);
 };
 
-const struct mlx5_glue *mlx5_glue;
+extern const struct mlx5_glue *mlx5_glue;
 
 #endif /* MLX5_GLUE_H_ */
-- 
2.26.0