[PATCH v3 1/1] eal: add C++ include guard in generic/rte_vect.h

[Ashish Sadanandan]

The header was missing the extern "C" directive which causes name
mangling of functions by C++ compilers, leading to linker errors
complaining of undefined references to these functions.

Also updated the coding style contribution guideline with a new
"Language Linkage" section stating `extern "C"` block should be added to
public headers.

Fixes: 86c743cf9140 ("eal: define generic vector types")
Cc: nelio.laranjeiro at 6wind.com
Cc: stable at dpdk.org

Signed-off-by: Ashish Sadanandan <ashish.sadanandan at gmail.com>
---
 .mailmap                                 |  2 +-
 doc/guides/contributing/coding_style.rst | 21 +++++++++++++++++++++
 lib/eal/include/generic/rte_vect.h       |  8 ++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/.mailmap b/.mailmap
index 50726e1232..24de59ba89 100644
--- a/.mailmap
+++ b/.mailmap
@@ -142,7 +142,7 @@ Ashijeet Acharya <ashijeet.acharya at 6wind.com>
 Ashish Gupta <ashishg at marvell.com> <ashish.gupta at marvell.com> <ashish.gupta at caviumnetworks.com>
 Ashish Jain <ashish.jain at nxp.com>
 Ashish Paul <apaul at juniper.net>
-Ashish Sadanandan <ashish.sadanandan at gmail.com>
+Ashish Sadanandan <ashish.sadanandan at gmail.com> <quic_asadanan at quicinc.com>
 Ashish Shah <ashish.n.shah at intel.com>
 Ashwin Sekhar T K <asekhar at marvell.com> <ashwin.sekhar at caviumnetworks.com>
 Asim Jamshed <asim.jamshed at gmail.com>
diff --git a/doc/guides/contributing/coding_style.rst b/doc/guides/contributing/coding_style.rst
index 1ebc79ca3c..27c947fcec 100644
--- a/doc/guides/contributing/coding_style.rst
+++ b/doc/guides/contributing/coding_style.rst
@@ -106,6 +106,27 @@ Headers should be protected against multiple inclusion with the usual:
 
    #endif /* _FILE_H_ */
 
+Language Linkage
+~~~~~~~~~~~~~~~~
+
+Public headers should enclose all function and variable declarations and definitions in an ``extern "C"`` block to facilitate interoperability with C++.
+
+.. code-block:: c
+
+   #ifndef _FILE_H_
+   #define _FILE_H_
+
+   #ifdef __cplusplus
+   extern "C" {
+   #endif
+
+   /* Code */
+
+   #ifdef __cplusplus
+   }
+   #endif
+
+   #endif /* _FILE_H_ */
 
 Macros
 ~~~~~~
diff --git a/lib/eal/include/generic/rte_vect.h b/lib/eal/include/generic/rte_vect.h
index 6540419cd2..3578d8749b 100644
--- a/lib/eal/include/generic/rte_vect.h
+++ b/lib/eal/include/generic/rte_vect.h
@@ -15,6 +15,10 @@
 
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #ifndef RTE_TOOLCHAIN_MSVC
 
 /* Unsigned vector types */
@@ -226,4 +230,8 @@ uint16_t rte_vect_get_max_simd_bitwidth(void);
  */
 int rte_vect_set_max_simd_bitwidth(uint16_t bitwidth);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _RTE_VECT_H_ */
-- 
2.31.1