[PATCH 2/3] eal: import and export data variables for MSVC

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

MSVC requires that data variables be explicitly declared as either
imported or exported. Provide macros that allow dpdk to correctly
declare data variables as exported for itself and imported for
applications.

Use new per-library macro to declare variables exported or imported for
per-lcore data variables.

Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
 lib/eal/include/meson.build      |  1 +
 lib/eal/include/rte_common.h     |  8 ++++++++
 lib/eal/include/rte_eal.h        |  2 ++
 lib/eal/include/rte_eal_export.h | 23 +++++++++++++++++++++++
 lib/eal/include/rte_errno.h      |  2 ++
 lib/eal/version.map              |  6 +++---
 lib/meson.build                  |  2 ++
 7 files changed, 41 insertions(+), 3 deletions(-)
 create mode 100644 lib/eal/include/rte_eal_export.h

diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build
index e94b056..376ae81 100644
--- a/lib/eal/include/meson.build
+++ b/lib/eal/include/meson.build
@@ -16,6 +16,7 @@ headers += files(
         'rte_dev.h',
         'rte_devargs.h',
         'rte_eal.h',
+        'rte_eal_export.h',
         'rte_eal_memconfig.h',
         'rte_eal_trace.h',
         'rte_errno.h',
diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
index 298a5c6..ad80122 100644
--- a/lib/eal/include/rte_common.h
+++ b/lib/eal/include/rte_common.h
@@ -26,6 +26,14 @@
 /* OS specific include */
 #include <rte_os.h>
 
+#ifdef RTE_TOOLCHAIN_MSVC
+#define __rte_declare_import __declspec(dllimport)
+#define __rte_declare_export __declspec(dllexport)
+#else
+#define __rte_declare_import
+#define __rte_declare_export
+#endif
+
 #ifndef RTE_TOOLCHAIN_MSVC
 #ifndef typeof
 #define typeof __typeof__
diff --git a/lib/eal/include/rte_eal.h b/lib/eal/include/rte_eal.h
index c2256f8..d0dc91b 100644
--- a/lib/eal/include/rte_eal.h
+++ b/lib/eal/include/rte_eal.h
@@ -16,6 +16,7 @@
 
 #include <rte_config.h>
 #include <rte_compat.h>
+#include <rte_eal_export.h>
 #include <rte_per_lcore.h>
 #include <rte_uuid.h>
 
@@ -426,6 +427,7 @@ typedef int (*rte_mp_async_reply_t)(const struct rte_mp_msg *request,
  */
 int rte_sys_gettid(void);
 
+__rte_eal_export
 RTE_DECLARE_PER_LCORE(int, _thread_id);
 
 /**
diff --git a/lib/eal/include/rte_eal_export.h b/lib/eal/include/rte_eal_export.h
new file mode 100644
index 0000000..3901760
--- /dev/null
+++ b/lib/eal/include/rte_eal_export.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2024 Microsoft Corporation
+ */
+
+#ifndef _RTE_EAL_EXPORT_H_
+#define _RTE_EAL_EXPORT_H_
+
+/**
+ * @file
+ *
+ * Import / Export macros for eal data variables.
+ */
+
+#include <rte_common.h>
+
+#ifndef __rte_eal_export
+#define __rte_eal_export __rte_declare_import
+#else
+#undef __rte_eal_export
+#define __rte_eal_export __rte_declare_export
+#endif
+
+#endif
diff --git a/lib/eal/include/rte_errno.h b/lib/eal/include/rte_errno.h
index ba45591..311732f 100644
--- a/lib/eal/include/rte_errno.h
+++ b/lib/eal/include/rte_errno.h
@@ -15,8 +15,10 @@
 extern "C" {
 #endif
 
+#include <rte_eal_export.h>
 #include <rte_per_lcore.h>
 
+__rte_eal_export
 RTE_DECLARE_PER_LCORE(int, _rte_errno); /**< Per core error number. */
 
 /**
diff --git a/lib/eal/version.map b/lib/eal/version.map
index c06ceaa..62914d2 100644
--- a/lib/eal/version.map
+++ b/lib/eal/version.map
@@ -4,9 +4,9 @@ DPDK_24 {
 	__rte_panic;
 	eal_parse_sysfs_value; # WINDOWS_NO_EXPORT
 	eal_timer_source; # WINDOWS_NO_EXPORT
-	per_lcore__lcore_id;
-	per_lcore__rte_errno;
-	per_lcore__thread_id;
+	per_lcore__lcore_id; # MSVC_NO_EXPORT
+	per_lcore__rte_errno; # MSVC_NO_EXPORT
+	per_lcore__thread_id; # MSVC_NO_EXPORT
 	rte_bus_dump;
 	rte_bus_find;
 	rte_bus_find_by_device;
diff --git a/lib/meson.build b/lib/meson.build
index f8836a4..f8d88d2 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -235,6 +235,8 @@ foreach l:libraries
         cflags += '-Wthread-safety'
     endif
 
+    cflags += '-D__rte_@0@_export'.format(name)
+
     # first build static lib
     static_lib = static_library(libname,
             sources,
-- 
1.8.3.1