Only set the COMPILER_HAS_HIDDEN_VISIBILITY if GCC >= 4.2

Hearsay has it that before that version it didn't work properly.

Hopefully this will fix more dashboard builds.

Modules/GenerateExportHeader.cmake

@@ -116,10 +116,28 @@ include(CMakeParseArguments)
 include(CheckCXXCompilerFlag)
 
 macro(_test_compiler_hidden_visibility)
-  check_cxx_compiler_flag(-fvisibility=hidden COMPILER_HAS_HIDDEN_VISIBILITY)
-  check_cxx_compiler_flag(-fvisibility-inlines-hidden COMPILER_HAS_HIDDEN_INLINE_VISIBILITY)
-  option(USE_COMPILER_HIDDEN_VISIBILITY "Use HIDDEN visibility support if available." ON)
-  mark_as_advanced(USE_COMPILER_HIDDEN_VISIBILITY)
+
+  if (CMAKE_COMPILER_IS_GNUCXX)
+    exec_program(${CMAKE_C_COMPILER} ARGS --version OUTPUT_VARIABLE     _gcc_version_info)
+    string (REGEX MATCH "[345]\\.[0-9]\\.[0-9]" _gcc_version "${_gcc_version_info}")
+    # gcc on mac just reports: "gcc (GCC) 3.3 20030304 ..." without the
+    # patch level, handle this here:
+    if(NOT _gcc_version)
+      string (REGEX REPLACE ".*\\(GCC\\).* ([34]\\.[0-9]) .*" "\\1.0" _gcc_version "${_gcc_version_info}")
+    endif()
+
+    if(${_gcc_version} VERSION_LESS "4.2")
+      set(GCC_TOO_OLD TRUE)
+      message(WARNING "GCC version older than 4.2")
+    endif()
+  endif()
+
+  if (NOT GCC_TOO_OLD)
+    check_cxx_compiler_flag(-fvisibility=hidden COMPILER_HAS_HIDDEN_VISIBILITY)
+    check_cxx_compiler_flag(-fvisibility-inlines-hidden COMPILER_HAS_HIDDEN_INLINE_VISIBILITY)
+    option(USE_COMPILER_HIDDEN_VISIBILITY "Use HIDDEN visibility support if available." ON)
+    mark_as_advanced(USE_COMPILER_HIDDEN_VISIBILITY)
+  endif()
 endmacro()
 
 set(myDir ${CMAKE_CURRENT_LIST_DIR})
@@ -233,21 +251,6 @@ function(add_compiler_export_flags)
     return()
   endif()
 
-  if (CMAKE_COMPILER_IS_GNUCXX)
-    exec_program(${CMAKE_C_COMPILER} ARGS --version OUTPUT_VARIABLE     _gcc_version_info)
-    string (REGEX MATCH "[345]\\.[0-9]\\.[0-9]" _gcc_version "${_gcc_version_info}")
-    # gcc on mac just reports: "gcc (GCC) 3.3 20030304 ..." without the
-    # patch level, handle this here:
-    if(NOT _gcc_version)
-      string (REGEX REPLACE ".*\\(GCC\\).* ([34]\\.[0-9]) .*" "\\1.0" _gcc_version "${_gcc_version_info}")
-    endif()
-
-    if(${_gcc_version} VERSION_LESS "4.2")
-      message(WARNING "GCC version older than 4.2")
-      return()
-    endif()
-  endif()
-
   set (EXTRA_FLAGS "-fvisibility=hidden")
 
   if(COMPILER_HAS_HIDDEN_INLINE_VISIBILITY)

Tests/Module/GenerateExportHeader/CMakeLists.txt

@@ -76,24 +76,9 @@ macro(_do_build Include Library LibrarySource Source)
   )
 endmacro()
 
-if (CMAKE_COMPILER_IS_GNUCXX)
-  exec_program(${CMAKE_C_COMPILER} ARGS --version OUTPUT_VARIABLE     _gcc_version_info)
-  string (REGEX MATCH "[345]\\.[0-9]\\.[0-9]" _gcc_version "${_gcc_version_info}")
-  # gcc on mac just reports: "gcc (GCC) 3.3 20030304 ..." without the
-  # patch level, handle this here:
-  if(NOT _gcc_version)
-    string (REGEX REPLACE ".*\\(GCC\\).* ([34]\\.[0-9]) .*" "\\1.0" _gcc_version "${_gcc_version_info}")
-  endif()
-
-  if(${_gcc_version} VERSION_LESS "4.2")
-    set(GCC_IS_LESS_THAN_4_2 TRUE)
-    message(WARNING "GCC version older than 4.2. Actual version: ${_gcc_version}")
-  endif()
-endif()
-
 macro(build_fail Include Library LibrarySource Source Message)
   _do_build(${Include} ${Library} ${LibrarySource} "${Source}")
-  if(NOT GCC_IS_LESS_THAN_4_2 AND (USE_COMPILER_HIDDEN_VISIBILITY AND COMPILER_HAS_HIDDEN_VISIBILITY) OR WIN32 OR (${CMAKE_CXX_COMPILER_ID} MATCHES Clang))
+  if(COMPILER_HAS_HIDDEN_VISIBILITY OR WIN32 OR (${CMAKE_CXX_COMPILER_ID} MATCHES Clang))
     test_fail(Result ${Message})
   else()
     test_pass(Result ${Message})