curl/CMake/CurlSymbolHiding.cmake

include(CheckCSourceCompiles)

option(CURL_HIDDEN_SYMBOLS "Set to ON to hide libcurl internal symbols (=hide all symbols that aren't officially external)." ON)
mark_as_advanced(CURL_HIDDEN_SYMBOLS)

if(CURL_HIDDEN_SYMBOLS)
    set(SUPPORTS_SYMBOL_HIDING FALSE)

    if(CMAKE_C_COMPILER_ID MATCHES "Clang")
        set(SUPPORTS_SYMBOL_HIDING TRUE)
        set(_SYMBOL_EXTERN "__attribute__ ((__visibility__ (\"default\")))")
        set(_CFLAG_SYMBOLS_HIDE "-fvisibility=hidden")
    elseif(CMAKE_COMPILER_IS_GNUCC)
        if(NOT CMAKE_VERSION VERSION_LESS 2.8.10)
            set(GCC_VERSION ${CMAKE_C_COMPILER_VERSION})
        else()
            execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion
                            OUTPUT_VARIABLE GCC_VERSION)
        endif()
        if(NOT GCC_VERSION VERSION_LESS 3.4)
            # note: this is considered buggy prior to 4.0 but the autotools don't care, so let's ignore that fact
            set(SUPPORTS_SYMBOL_HIDING TRUE)
            set(_SYMBOL_EXTERN "__attribute__ ((__visibility__ (\"default\")))")
            set(_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'm not 100% sure
        #       so let's to 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()
    elseif(MSVC)
        set(SUPPORTS_SYMBOL_HIDING TRUE)
    endif()

    set(HIDES_CURL_PRIVATE_SYMBOLS ${SUPPORTS_SYMBOL_HIDING})
elseif(MSVC)
    if(NOT CMAKE_VERSION VERSION_LESS 3.7)
        set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE) #present since 3.4.3 but broken
        set(HIDES_CURL_PRIVATE_SYMBOLS FALSE)
    else()
        message(WARNING "Hiding private symbols regardless CURL_HIDDEN_SYMBOLS being disabled.")
        set(HIDES_CURL_PRIVATE_SYMBOLS TRUE)
    endif()
elseif()
    set(HIDES_CURL_PRIVATE_SYMBOLS FALSE)
endif()

set(CURL_CFLAG_SYMBOLS_HIDE ${_CFLAG_SYMBOLS_HIDE})
set(CURL_EXTERN_SYMBOL ${_SYMBOL_EXTERN})