Commit 6140dfcf authored by Jakub Zakrzewski's avatar Jakub Zakrzewski
Browse files

CMake: Try to (un-)hide private library symbols 

Detect support for compiler symbol visibility flags and apply those
according to CURL_HIDDEN_SYMBOLS option.
It should work true to the autotools build except it tries to unhide
symbols on Windows when requested and prints warning if it fails.

Ref: https://github.com/curl/curl/issues/981#issuecomment-242665951
Reported-by: Daniel Stenberg
parent 83ef21e5

CMake/CurlSymbolHiding.cmake

0 → 100644
+61 −0
Original line number Diff line number Diff line 
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})

CMakeLists.txt

+1 −2
Original line number Diff line number Diff line
@@ -119,8 +119,7 @@ if(MSVC) 
  mark_as_advanced(BUILD_RELEASE_DEBUG_DIRS)

endif()



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)

include(CurlSymbolHiding)



option(HTTP_ONLY "disables all protocols except HTTP (This overrides all CURL_DISABLE_* options)" OFF)

mark_as_advanced(HTTP_ONLY)

lib/CMakeLists.txt

+5 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ endif() 


set_target_properties(${LIB_NAME} PROPERTIES COMPILE_DEFINITIONS BUILDING_LIBCURL)



if(HIDES_CURL_PRIVATE_SYMBOLS)

  set_property(TARGET ${LIB_NAME} APPEND PROPERTY COMPILE_DEFINITIONS "CURL_HIDDEN_SYMBOLS")

  set_property(TARGET ${LIB_NAME} APPEND PROPERTY COMPILE_FLAGS ${CURL_CFLAG_SYMBOLS_HIDE})

endif()



# Remove the "lib" prefix since the library is already named "libcurl".

set_target_properties(${LIB_NAME} PROPERTIES PREFIX "")

set_target_properties(${LIB_NAME} PROPERTIES IMPORT_PREFIX "")

lib/curl_config.h.cmake

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ 
#cmakedefine CURL_DISABLE_VERBOSE_STRINGS 1



/* to make a symbol visible */

#cmakedefine CURL_EXTERN_SYMBOL 1

#cmakedefine CURL_EXTERN_SYMBOL ${CURL_EXTERN_SYMBOL}

/* Ensure using CURL_EXTERN_SYMBOL is possible */

#ifndef CURL_EXTERN_SYMBOL

#define CURL_EXTERN_SYMBOL

tests/libtest/CMakeLists.txt

+4 −0
Original line number Diff line number Diff line
@@ -43,6 +43,10 @@ if(NOT WIN32) 
  # library at (tests)/libtest/.libs/libhostname.so

  set_target_properties(hostname PROPERTIES

      LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/.libs)

  if(HIDES_CURL_PRIVATE_SYMBOLS)

    set_property(TARGET hostname APPEND PROPERTY COMPILE_DEFINITIONS "CURL_HIDDEN_SYMBOLS")

    set_property(TARGET hostname APPEND PROPERTY COMPILE_FLAGS ${CURL_CFLAG_SYMBOLS_HIDE})

  endif()

endif()



# # files used only in some libcurl test programs