dnf5: Define macros for assigning symbol visibility

dnf5/include/dnf5/defs.h

@@ -0,0 +1,59 @@
+/*
+Copyright Contributors to the libdnf project.
+
+This file is part of libdnf: https://github.com/rpm-software-management/libdnf/
+
+Libdnf is free software: you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation, either version 2.1 of the License, or
+(at your option) any later version.
+
+Libdnf is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifndef DNF5_DEFS_H
+#define DNF5_DEFS_H
+
+// Generic helper definitions for shared library support
+#if defined _WIN32 || defined __CYGWIN__
+#define DNF_SYMBOL_IMPORT __declspec(dllimport)
+#define DNF_SYMBOL_EXPORT __declspec(dllexport)
+#define DNF_SYMBOL_LOCAL
+#else
+#if __GNUC__ >= 4
+#define DNF_SYMBOL_IMPORT __attribute__((visibility("default")))
+#define DNF_SYMBOL_EXPORT __attribute__((visibility("default")))
+#define DNF_SYMBOL_LOCAL  __attribute__((visibility("hidden")))
+#else
+#define DNF_SYMBOL_IMPORT
+#define DNF_SYMBOL_EXPORT
+#define DNF_SYMBOL_LOCAL
+#endif
+#endif
+
+// Now define DNF_API, DNF_LOCAL and DNF_PLUGIN_API.
+// DNF_API and DNF_PLUGIN_API are used for public API symbols. It either imports or exports the symbol.
+// DNF_LOCAL is used for non-api symbols.
+
+#ifdef DNF_BUILD_APPLICATION  // defined if we are building the dnf application
+#define DNF_API DNF_SYMBOL_EXPORT
+#else
+#define DNF_API DNF_SYMBOL_IMPORT
+#endif
+
+#define DNF_LOCAL DNF_SYMBOL_LOCAL
+
+// DNF exports its symbols but imports plugin symbols.
+#ifdef DNF_BUILD_APPLICATION  // defined if we are building the dnf application
+#define DNF_PLUGIN_API DNF_SYMBOL_IMPORT
+#else
+#define DNF_PLUGIN_API DNF_SYMBOL_EXPORT
+#endif
+
+#endif