try_compile: Add support for using ALIAS targets

Fixes: #25337
Signed-off-by: Cristian Le <cristian.le@mpsd.mpg.de>

Help/command/try_compile.rst

@@ -177,6 +177,9 @@ The options for the above signatures are:
   If this option is specified, any ``-DLINK_LIBRARIES=...`` value
   given to the ``CMAKE_FLAGS`` option will be ignored.
 
+  .. versionadded:: 3.29
+    Alias targets to imported libraries are also supported.
+
 ``LINK_OPTIONS <options>...``
   .. versionadded:: 3.14
 

Source/cmCoreTryCompile.cxx

@@ -856,8 +856,30 @@ cm::optional<cmTryCompileResult> cmCoreTryCompile::TryCompileCode(
         fclose(fout);
         return cm::nullopt;
       }
-      fprintf(fout, "\ninclude(\"${CMAKE_CURRENT_LIST_DIR}/%s\")\n\n",
+      fprintf(fout, "\ninclude(\"${CMAKE_CURRENT_LIST_DIR}/%s\")\n",
               fname.c_str());
+      // Create all relevant alias targets
+      if (arguments.LinkLibraries) {
+        const auto& aliasTargets = this->Makefile->GetAliasTargets();
+        for (std::string const& i : *arguments.LinkLibraries) {
+          auto alias = aliasTargets.find(i);
+          if (alias != aliasTargets.end()) {
+            const auto& aliasTarget =
+              this->Makefile->FindTargetToUse(alias->second);
+            // Create equivalent library/executable alias
+            if (aliasTarget->GetType() == cmStateEnums::EXECUTABLE) {
+              fprintf(fout, "add_executable(\"%s\" ALIAS \"%s\")\n", i.c_str(),
+                      alias->second.c_str());
+            } else {
+              // Other cases like UTILITY and GLOBAL_TARGET are excluded when
+              // arguments.LinkLibraries is initially parsed in this function.
+              fprintf(fout, "add_library(\"%s\" ALIAS \"%s\")\n", i.c_str(),
+                      alias->second.c_str());
+            }
+          }
+        }
+      }
+      fprintf(fout, "\n");
     }
 
     /* Set the appropriate policy information for ENABLE_EXPORTS */

Tests/ExportImport/Import/A/CMakeLists.txt

@@ -518,6 +518,91 @@ if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREA
       endif()
     endif()
   endif()
+
+  # Testing try_compile with ALIAS targets.
+  # These assume that previous test were successful, or at least the failures will be at the linking stage
+  # with symbol not found errors
+
+  # First make sure that if the test run without appropriate alias targets, they should error out
+  try_compile(FAILING_LIBRARY_ALIAS_ERROR_VARIABLE
+          "${CMAKE_CURRENT_BINARY_DIR}/test_failing_library_alias"
+          "${CMAKE_CURRENT_SOURCE_DIR}/test_system.cpp"
+          LINK_LIBRARIES not_existing_library
+          OUTPUT_VARIABLE OUTPUT
+          NO_CACHE
+  )
+  if(FAILING_LIBRARY_ALIAS_ERROR_VARIABLE)
+    message(SEND_ERROR "FAILING_LIBRARY_ALIAS_ERROR_VARIABLE try_compile succeeded, but it was expected to fail ${OUTPUT}.")
+  endif()
+
+  # FIXME: CMAKE_TRY_COMPILE_TARGET_TYPE=MODULE is needed to properly link and test targets linked to an executable
+#  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+#  try_compile(FAILING_EXE_ALIAS_ERROR_VARIABLE
+#          "${CMAKE_CURRENT_BINARY_DIR}/test_failing_exe_alias"
+#          "${CMAKE_CURRENT_SOURCE_DIR}/imp_mod1.c"
+#          LINK_LIBRARIES not_existing_executable
+#          OUTPUT_VARIABLE OUTPUT
+#          NO_CACHE
+#  )
+#  unset(CMAKE_TRY_COMPILE_TARGET_TYPE)
+#  if(FAILING_EXE_ALIAS_ERROR_VARIABLE)
+#    message(SEND_ERROR "FAILING_EXE_ALIAS_ERROR_VARIABLE try_compile succeeded, but it was expected to fail ${OUTPUT}.")
+#  endif()
+
+  # Do the actual try_compile tests for ALIAS targets
+  add_library(exp_systemlib_alias ALIAS exp_systemlib)
+  try_compile(EXP_LIBRARY_ALIAS_ERROR_VARIABLE
+          "${CMAKE_CURRENT_BINARY_DIR}/test_library_alias"
+          "${CMAKE_CURRENT_SOURCE_DIR}/test_system.cpp"
+          LINK_LIBRARIES exp_systemlib_alias
+          OUTPUT_VARIABLE OUTPUT
+          NO_CACHE
+  )
+  if(NOT EXP_LIBRARY_ALIAS_ERROR_VARIABLE)
+    message(SEND_ERROR "EXP_LIBRARY_ALIAS_ERROR_VARIABLE try_compile failed with library aliased target, but it was expected to succeed ${OUTPUT}.")
+  endif()
+
+  # FIXME: CMAKE_TRY_COMPILE_TARGET_TYPE=MODULE is needed to properly link and test targets linked to an executable
+#  set(CMAKE_TRY_COMPILE_TARGET_TYPE MODULE)
+#  add_executable(exp_exe_alias ALIAS exp_testExe2)
+#  try_compile(EXP_EXE_ALIAS_ERROR_VARIABLE
+#          "${CMAKE_CURRENT_BINARY_DIR}/test_exe_alias"
+#          "${CMAKE_CURRENT_SOURCE_DIR}/imp_mod1.c"
+#          LINK_LIBRARIES exp_exe_alias
+#          OUTPUT_VARIABLE OUTPUT
+#          NO_CACHE
+#  )
+#  unset(CMAKE_TRY_COMPILE_TARGET_TYPE)
+#  if(NOT EXP_EXE_ALIAS_ERROR_VARIABLE)
+#    message(SEND_ERROR "EXP_EXE_ALIAS_ERROR_VARIABLE try_compile failed with executable aliased target, but it was expected to succeed ${OUTPUT}.")
+#  endif()
+
+  add_library(bld_systemlib_alias ALIAS bld_systemlib)
+  try_compile(BLD_LIBRARY_ALIAS_ERROR_VARIABLE
+          "${CMAKE_CURRENT_BINARY_DIR}/test_library_alias"
+          "${CMAKE_CURRENT_SOURCE_DIR}/test_system.cpp"
+          LINK_LIBRARIES bld_systemlib_alias
+          OUTPUT_VARIABLE OUTPUT
+          NO_CACHE
+  )
+  if(NOT BLD_LIBRARY_ALIAS_ERROR_VARIABLE)
+    message(SEND_ERROR "BLD_LIBRARY_ALIAS_ERROR_VARIABLE try_compile failed with library aliased target, but it was expected to succeed. ${OUTPUT}")
+  endif()
+
+  # FIXME: CMAKE_TRY_COMPILE_TARGET_TYPE=MODULE is needed to properly link and test targets linked to an executable
+#  set(CMAKE_TRY_COMPILE_TARGET_TYPE MODULE)
+#  add_executable(bld_exe_alias ALIAS bld_testExe2)
+#  try_compile(BLD_EXE_ALIAS_ERROR_VARIABLE
+#          "${CMAKE_CURRENT_BINARY_DIR}/test_exe_alias"
+#          "${CMAKE_CURRENT_SOURCE_DIR}/imp_mod1.c"
+#          LINK_LIBRARIES bld_exe_alias
+#          OUTPUT_VARIABLE OUTPUT
+#          NO_CACHE
+#  )
+#  unset(CMAKE_TRY_COMPILE_TARGET_TYPE)
+#  if(NOT BLD_EXE_ALIAS_ERROR_VARIABLE)
+#    message(SEND_ERROR "BLD_EXE_ALIAS_ERROR_VARIABLE try_compile failed with executable aliased target, but it was expected to succeed. ${OUTPUT}")
+#  endif()
 endif()
 
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