From 5235554eb4071c798fef9b29f46e9c96970055ea Mon Sep 17 00:00:00 2001
From: Yuri Gribov <tetra2005@gmail.com>
Date: Sun, 3 Jul 2022 10:54:39 +0300
Subject: Hide internal symbols on platforms that support visibility
 annotations (see discussion in gh-1017).

---
 CMakeLists.txt             | 11 +++++++++++
 configure.ac               | 12 ++++++++++++
 libarchive/archive.h       |  2 ++
 libarchive/archive_entry.h |  2 ++
 4 files changed, 27 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e1ff575..df83ed18 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2024,6 +2024,17 @@ CHECK_CRYPTO("MD5;RMD160;SHA1;SHA256;SHA512" LIBMD)
 
 CHECK_CRYPTO_WIN("MD5;SHA1;SHA256;SHA384;SHA512")
 
+# Check visibility annotations
+SET(OLD_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
+SET(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fvisibility=hidden -Werror")
+CHECK_C_SOURCE_COMPILES("void __attribute__((visibility(\"default\"))) foo(void);
+int main() { return 0; }" HAVE_VISIBILITY_ATTR)
+IF (HAVE_VISIBILITY_ATTR)
+  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden")
+  ADD_DEFINITIONS(-D__LIBARCHIVE_ENABLE_VISIBILITY)
+ENDIF(HAVE_VISIBILITY_ATTR)
+SET(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
+
 # Generate "config.h" from "build/cmake/config.h.in"
 CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/build/cmake/config.h.in
 	${CMAKE_CURRENT_BINARY_DIR}/config.h)
diff --git a/configure.ac b/configure.ac
index b30430d2..cc51badc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1247,6 +1247,18 @@ case "$host_os" in
 	;;
 esac
 
+dnl Visibility annotations...
+saved_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -fvisibility=hidden -Werror"
+AC_MSG_CHECKING(whether compiler supports visibility annotations)
+AC_LINK_IFELSE([AC_LANG_PROGRAM([
+                 int foo( void ) __attribute__((visibility("default")));
+               ])],
+               [CFLAGS="$saved_CFLAGS -fvisibility=hidden -D__LIBARCHIVE_ENABLE_VISIBILITY";
+                AC_MSG_RESULT(yes)],
+               [CFLAGS="$saved_CFLAGS"
+                AC_MSG_RESULT(no)])
+
 # Ensure test directories are present if building out-of-tree
 AC_CONFIG_COMMANDS([mkdirs],
 		   [mkdir -p libarchive/test tar/test cat/test cpio/test])
diff --git a/libarchive/archive.h b/libarchive/archive.h
index 7f58a1f2..dcb8b0df 100644
--- a/libarchive/archive.h
+++ b/libarchive/archive.h
@@ -120,6 +120,8 @@ typedef ssize_t la_ssize_t;
 #   define __LA_DECL	__declspec(dllimport)
 #  endif
 # endif
+#elif defined __LIBARCHIVE_ENABLE_VISIBILITY
+#  define __LA_DECL __attribute__((visibility("default")))
 #else
 /* Static libraries or non-Windows needs no special declaration. */
 # define __LA_DECL
diff --git a/libarchive/archive_entry.h b/libarchive/archive_entry.h
index 450b3cf9..e579e9f3 100644
--- a/libarchive/archive_entry.h
+++ b/libarchive/archive_entry.h
@@ -122,6 +122,8 @@ typedef ssize_t la_ssize_t;
 #   define __LA_DECL	__declspec(dllimport)
 #  endif
 # endif
+#elif defined __LIBARCHIVE_ENABLE_VISIBILITY
+#  define __LA_DECL __attribute__((visibility("default")))
 #else
 /* Static libraries on all platforms and shared libraries on non-Windows. */
 # define __LA_DECL
-- 
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