cmake: tidy up and shorten symbol hiding initialization

- drop redundant local variables.

- drop extra Intel C feature check that always returned success due
  to not passing the tested compiler option. Nobody reported an issue
  with this since 2016, suggesting the version check alone is enough.

Closes #15400

diff --git a/CMake/CurlSymbolHiding.cmake b/CMake/CurlSymbolHiding.cmake
index 00b7b3c106cb3342edefe039d0a0dc693db544f7..7668bb83577da2625dc0c87c98bda7879d10d8db 100644 (file)
--- a/CMake/CurlSymbolHiding.cmake
+++ b/CMake/CurlSymbolHiding.cmake
@@ -21,8 +21,6 @@
 # SPDX-License-Identifier: curl
 #
 ###########################################################################
-include(CheckCSourceCompiles)
-
 option(CURL_HIDDEN_SYMBOLS "Hide libcurl internal symbols (=hide all symbols that are not officially external)" ON)
 mark_as_advanced(CURL_HIDDEN_SYMBOLS)
 
@@ -33,48 +31,35 @@ if(WIN32 AND (ENABLE_DEBUG OR ENABLE_CURLDEBUG))
   set(CURL_HIDDEN_SYMBOLS OFF)
 endif()
 
-if(CURL_HIDDEN_SYMBOLS)
-  set(_supports_symbol_hiding FALSE)
+set(CURL_HIDES_PRIVATE_SYMBOLS FALSE)
+unset(CURL_EXTERN_SYMBOL)
+unset(CURL_CFLAG_SYMBOLS_HIDE)
 
+if(CURL_HIDDEN_SYMBOLS)
   if(CMAKE_C_COMPILER_ID MATCHES "Clang" AND NOT MSVC)
-    set(_supports_symbol_hiding TRUE)
-    set(_symbol_extern "__attribute__ ((__visibility__ (\"default\")))")
-    set(_cflag_symbols_hide "-fvisibility=hidden")
+    set(CURL_HIDES_PRIVATE_SYMBOLS TRUE)
+    set(CURL_EXTERN_SYMBOL "__attribute__ ((__visibility__ (\"default\")))")
+    set(CURL_CFLAG_SYMBOLS_HIDE "-fvisibility=hidden")
   elseif(CMAKE_COMPILER_IS_GNUCC)
     if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
       # Note: This is considered buggy prior to 4.0 but the autotools do not care, so let us ignore that fact
-      set(_supports_symbol_hiding TRUE)
-      set(_symbol_extern "__attribute__ ((__visibility__ (\"default\")))")
-      set(_cflag_symbols_hide "-fvisibility=hidden")
+      set(CURL_HIDES_PRIVATE_SYMBOLS TRUE)
+      set(CURL_EXTERN_SYMBOL "__attribute__ ((__visibility__ (\"default\")))")
+      set(CURL_CFLAG_SYMBOLS_HIDE "-fvisibility=hidden")
     endif()
   elseif(CMAKE_C_COMPILER_ID MATCHES "SunPro" AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 8.0)
-    set(_supports_symbol_hiding TRUE)
-    set(_symbol_extern "__global")
-    set(_cflag_symbols_hide "-xldscope=hidden")
-  elseif(CMAKE_C_COMPILER_ID MATCHES "Intel" AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.0)
-    # Note: This should probably just check for version 9.1.045 but I am not 100% sure
-    #       so let us do it the same way autotools do.
-    set(_supports_symbol_hiding TRUE)
-    set(_symbol_extern "__attribute__ ((__visibility__ (\"default\")))")
-    set(_cflag_symbols_hide "-fvisibility=hidden")
-    check_c_source_compiles("#include <stdio.h>
-      int main(void) { printf(\"icc fvisibility bug test\"); return 0; }" _no_bug)
-    if(NOT _no_bug)
-      set(_supports_symbol_hiding FALSE)
-      set(_symbol_extern "")
-      set(_cflag_symbols_hide "")
-    endif()
+    set(CURL_HIDES_PRIVATE_SYMBOLS TRUE)
+    set(CURL_EXTERN_SYMBOL "__global")
+    set(CURL_CFLAG_SYMBOLS_HIDE "-xldscope=hidden")
+  elseif(CMAKE_C_COMPILER_ID MATCHES "Intel" AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.0)  # Requires 9.1.045
+    set(CURL_HIDES_PRIVATE_SYMBOLS TRUE)
+    set(CURL_EXTERN_SYMBOL "__attribute__ ((__visibility__ (\"default\")))")
+    set(CURL_CFLAG_SYMBOLS_HIDE "-fvisibility=hidden")
   elseif(MSVC)
-    set(_supports_symbol_hiding TRUE)
+    set(CURL_HIDES_PRIVATE_SYMBOLS TRUE)
   endif()
-
-  set(CURL_HIDES_PRIVATE_SYMBOLS ${_supports_symbol_hiding})
 else()
   if(MSVC)
     set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)
   endif()
-  set(CURL_HIDES_PRIVATE_SYMBOLS FALSE)
 endif()
-
-set(CURL_CFLAG_SYMBOLS_HIDE ${_cflag_symbols_hide})
-set(CURL_EXTERN_SYMBOL ${_symbol_extern})