AIX: Explicitly compute executable exports for both XL and GNU

On AIX, symbols in executables must be exported in order to be visible
to modules (plugins) they load via `dlopen`.  Prior to policy `CMP0065`,
CMake linked all executables with flags to export symbols, but the NEW
behavior for that policy is to do so only for executables that have the
`ENABLE_EXPORTS` target property set.  In both cases, CMake has always
used the AIX linker option `-bexpall` option to export symbols from
executables.

This has worked fairly well with the XL compiler, but with the GNU
compiler it works only for C ABI symbols.  The reason is that `-bexpall`
does not export symbols starting in `_` but the GNU C++ ABI mangles all
symbols with a leading `_`.  Therefore we have only supported C ABI
plugins with the GNU compiler on AIX.  Some projects have tried to work
around this by replacing `-bexpall` with `-bexpfull`, but the latter
often exports symbols that we do not want exported.

Avoid using `-bexpall` for executables by instead using by our own
internal `ExportImportList` script to compute symbol export lists from
the object files to be linked into an executable.  Pass the explicitly
computed export list to the AIX linker's `-bE:...` option.  We already
do this for shared object exports.

Issue: #19163

2 files changed, 10 insertions, 2 deletions

diff --git a/Modules/Platform/AIX-GNU.cmake b/Modules/Platform/AIX-GNU.cmake
index beb928b..cec71a1 100644
--- a/Modules/Platform/AIX-GNU.cmake
+++ b/Modules/Platform/AIX-GNU.cmake
@@ -18,7 +18,7 @@ macro(__aix_compiler_gnu lang)
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG "-Wl,-blibpath:")
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG_SEP ":")
   string(APPEND CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS " -Wl,-G,-bnoipath")
-  set(CMAKE_SHARED_LIBRARY_LINK_${lang}_FLAGS "-Wl,-bexpall")
+  set(CMAKE_SHARED_LIBRARY_LINK_${lang}_FLAGS "-Wl,-bexpall") # CMP0065 old behavior
   set(CMAKE_${lang}_USE_IMPLICIT_LINK_DIRECTORIES_IN_RUNTIME_PATH 1)
 
   set(CMAKE_${lang}_LINK_FLAGS "-Wl,-bnoipath")
@@ -32,4 +32,8 @@ macro(__aix_compiler_gnu lang)
     "\"${CMAKE_ROOT}/Modules/Platform/AIX/ExportImportList\" -o <OBJECT_DIR>/objects.exp <OBJECTS>"
     "<CMAKE_${lang}_COMPILER> <CMAKE_SHARED_LIBRARY_${lang}_FLAGS> -Wl,-bE:<OBJECT_DIR>/objects.exp <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS> <SONAME_FLAG><TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>"
     )
+
+  set(CMAKE_${lang}_LINK_EXECUTABLE_WITH_EXPORTS
+    "\"${CMAKE_ROOT}/Modules/Platform/AIX/ExportImportList\" -o <OBJECT_DIR>/objects.exp <OBJECTS>"
+    "<CMAKE_${lang}_COMPILER> <FLAGS> <CMAKE_${lang}_LINK_FLAGS> -Wl,-bE:<OBJECT_DIR>/objects.exp <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")
 endmacro()
diff --git a/Modules/Platform/AIX-XL.cmake b/Modules/Platform/AIX-XL.cmake
index 569edf7..52292bd 100644
--- a/Modules/Platform/AIX-XL.cmake
+++ b/Modules/Platform/AIX-XL.cmake
@@ -18,7 +18,7 @@ macro(__aix_compiler_xl lang)
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG "-Wl,-blibpath:")
   set(CMAKE_SHARED_LIBRARY_RUNTIME_${lang}_FLAG_SEP ":")
   set(CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS "-G -Wl,-bnoipath")  # -shared
-  set(CMAKE_SHARED_LIBRARY_LINK_${lang}_FLAGS "-Wl,-bexpall")
+  set(CMAKE_SHARED_LIBRARY_LINK_${lang}_FLAGS "-Wl,-bexpall") # CMP0065 old behavior
   set(CMAKE_SHARED_LIBRARY_${lang}_FLAGS " ")
   set(CMAKE_SHARED_MODULE_${lang}_FLAGS  " ")
 
@@ -30,4 +30,8 @@ macro(__aix_compiler_xl lang)
     "\"${CMAKE_ROOT}/Modules/Platform/AIX/ExportImportList\" -o <OBJECT_DIR>/objects.exp <OBJECTS>"
     "<CMAKE_${lang}_COMPILER> <CMAKE_SHARED_LIBRARY_${lang}_FLAGS> -Wl,-bE:<OBJECT_DIR>/objects.exp <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS> <SONAME_FLAG><TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>"
     )
+
+  set(CMAKE_${lang}_LINK_EXECUTABLE_WITH_EXPORTS
+    "\"${CMAKE_ROOT}/Modules/Platform/AIX/ExportImportList\" -o <OBJECT_DIR>/objects.exp <OBJECTS>"
+    "<CMAKE_${lang}_COMPILER> <FLAGS> <CMAKE_${lang}_LINK_FLAGS> -Wl,-bE:<OBJECT_DIR>/objects.exp <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")
 endmacro()