From 9fb32528d65a6e90bc73c1b0ecbf475263b7e896 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 17 Oct 2020 15:18:54 -0400
Subject: [PATCH] Generate *_API compiler definitions for modules...

... So mod-foo defines FOO_API properly on the command line, for use in its
public header files; on Windows, appropriately expanding one way when compiling
the library, another way when compiling other code that uses it, so that all
will link correctly.
---
 .../cmake-modules/AudacityFunctions.cmake     | 43 ++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/cmake-proxies/cmake-modules/AudacityFunctions.cmake b/cmake-proxies/cmake-modules/AudacityFunctions.cmake
index 3fea7e2e0..b54e34ae0 100644
--- a/cmake-proxies/cmake-modules/AudacityFunctions.cmake
+++ b/cmake-proxies/cmake-modules/AudacityFunctions.cmake
@@ -221,6 +221,39 @@ function( audacity_append_common_compiler_options var )
    set( ${var} "${${var}}" PARENT_SCOPE )
 endfunction()
 
+function( import_export_symbol var module_name )
+   # compute, e.g. "TRACK_UI_API" from module name "mod-track-ui"
+   string( REGEX REPLACE "^mod-" "" symbol "${module_name}" )
+   string( TOUPPER "${symbol}" symbol )
+   string( REPLACE "-" "_" symbol "${symbol}" )
+   string( APPEND symbol "_API" )
+   set( "${var}" "${symbol}" PARENT_SCOPE )
+endfunction()
+
+function( import_symbol_define var module_name )
+   import_export_symbol( symbol "${module_name}" )
+   if( CMAKE_SYSTEM_NAME MATCHES "Windows" )
+      set( value "_declspec(dllimport)" )
+   elseif( HAVE_VISIBILITY )
+      set( value "__attribute__((visibility(\"default\")))" )
+   else()
+      set( value "" )
+   endif()
+   set( "${var}" "${symbol}=${value}" PARENT_SCOPE )
+endfunction()
+
+function( export_symbol_define var module_name )
+   import_export_symbol( symbol "${module_name}" )
+   if( CMAKE_SYSTEM_NAME MATCHES "Windows" )
+      set( value "_declspec(dllexport)" )
+   elseif( HAVE_VISIBILITY )
+      set( value "__attribute__((visibility(\"default\")))" )
+   else()
+      set( value "" )
+   endif()
+   set( "${var}" "${symbol}=${value}" PARENT_SCOPE )
+endfunction()
+
 function( audacity_module_fn NAME SOURCES IMPORT_TARGETS
    ADDITIONAL_DEFINES ADDITIONAL_LIBRARIES )
 
@@ -238,6 +271,14 @@ function( audacity_module_fn NAME SOURCES IMPORT_TARGETS
    endif()
    add_library( ${TARGET} ${LIBTYPE} )
 
+   export_symbol_define( export_symbol "${TARGET}" )
+   import_symbol_define( import_symbol "${TARGET}" )
+   set( DEFINES
+      ${ADDITIONAL_DEFINES}
+      PRIVATE "${export_symbol}"
+      INTERFACE "${import_symbol}"
+   )
+
    set( LOPTS
       PRIVATE
          $<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>
@@ -266,7 +307,7 @@ function( audacity_module_fn NAME SOURCES IMPORT_TARGETS
 
    organize_source( "${TARGET_ROOT}" "" "${SOURCES}" )
    target_sources( ${TARGET} PRIVATE ${SOURCES} )
-   target_compile_definitions( ${TARGET} PRIVATE ${ADDITIONAL_DEFINES} )
+   target_compile_definitions( ${TARGET} PRIVATE ${DEFINES} )
    target_compile_options( ${TARGET} ${OPTIONS} )
    target_include_directories( ${TARGET} PUBLIC ${TARGET_ROOT} )