enable_language: Assume compiler works if ABI detection compiles

We run a `try_compile` with a tiny test source to check if the compiler
works so that we can fail early if it does not.  When the compiler does
work, we immediately `try_compile` the ABI detection source.  In the
common case that both steps work, we gain no useful information from the
first one and the work was wasted.

Re-order the checks to try the ABI detection first.  If it works then
assume the compiler works and skip the dedicated check.  If the ABI
check fails then proceed with the normal test for a working compiler so
the diagnostic can be shown as before.

Fixes: #18703

1 files changed, 38 insertions, 37 deletions

diff --git a/Modules/CMakeTestCCompiler.cmake b/Modules/CMakeTestCCompiler.cmake
index eadea89..3734ec4 100644
--- a/Modules/CMakeTestCCompiler.cmake
+++ b/Modules/CMakeTestCCompiler.cmake
@@ -21,6 +21,15 @@ endif()
 # We now store this in CMakeCCompiler.cmake.
 unset(CMAKE_C_COMPILER_WORKS CACHE)
 
+# Try to identify the ABI and configure it into CMakeCCompiler.cmake
+include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerABI.cmake)
+CMAKE_DETERMINE_COMPILER_ABI(C ${CMAKE_ROOT}/Modules/CMakeCCompilerABI.c)
+if(CMAKE_C_ABI_COMPILED)
+  # The compiler worked so skip dedicated test below.
+  set(CMAKE_C_COMPILER_WORKS TRUE)
+  message(STATUS "Check for working C compiler: ${CMAKE_C_COMPILER} - skipped")
+endif()
+
 # This file is used by EnableLanguage in cmGlobalGenerator to
 # determine that that selected C compiler can actually compile
 # and link the most basic of programs.   If not, a fatal error
@@ -47,49 +56,41 @@ if(NOT CMAKE_C_COMPILER_WORKS)
   # Move result from cache to normal variable.
   set(CMAKE_C_COMPILER_WORKS ${CMAKE_C_COMPILER_WORKS})
   unset(CMAKE_C_COMPILER_WORKS CACHE)
-  set(C_TEST_WAS_RUN 1)
   __TestCompiler_restoreTryCompileTargetType()
-endif()
-
-if(NOT CMAKE_C_COMPILER_WORKS)
-  PrintTestCompilerResult(CHECK_FAIL "broken")
-  file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
-    "Determining if the C compiler works failed with "
-    "the following output:\n${__CMAKE_C_COMPILER_OUTPUT}\n\n")
-  string(REPLACE "\n" "\n  " _output "${__CMAKE_C_COMPILER_OUTPUT}")
-  message(FATAL_ERROR "The C compiler\n  \"${CMAKE_C_COMPILER}\"\n"
-    "is not able to compile a simple test program.\nIt fails "
-    "with the following output:\n  ${_output}\n\n"
-    "CMake will not be able to correctly generate this project.")
-else()
-  if(C_TEST_WAS_RUN)
-    PrintTestCompilerResult(CHECK_PASS "works")
-    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
-      "Determining if the C compiler works passed with "
+  if(NOT CMAKE_C_COMPILER_WORKS)
+    PrintTestCompilerResult(CHECK_FAIL "broken")
+    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+      "Determining if the C compiler works failed with "
       "the following output:\n${__CMAKE_C_COMPILER_OUTPUT}\n\n")
+    string(REPLACE "\n" "\n  " _output "${__CMAKE_C_COMPILER_OUTPUT}")
+    message(FATAL_ERROR "The C compiler\n  \"${CMAKE_C_COMPILER}\"\n"
+      "is not able to compile a simple test program.\nIt fails "
+      "with the following output:\n  ${_output}\n\n"
+      "CMake will not be able to correctly generate this project.")
   endif()
+  PrintTestCompilerResult(CHECK_PASS "works")
+  file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
+    "Determining if the C compiler works passed with "
+    "the following output:\n${__CMAKE_C_COMPILER_OUTPUT}\n\n")
+endif()
 
-  # Try to identify the ABI and configure it into CMakeCCompiler.cmake
-  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerABI.cmake)
-  CMAKE_DETERMINE_COMPILER_ABI(C ${CMAKE_ROOT}/Modules/CMakeCCompilerABI.c)
-  # Try to identify the compiler features
-  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompileFeatures.cmake)
-  CMAKE_DETERMINE_COMPILE_FEATURES(C)
+# Try to identify the compiler features
+include(${CMAKE_ROOT}/Modules/CMakeDetermineCompileFeatures.cmake)
+CMAKE_DETERMINE_COMPILE_FEATURES(C)
 
-  # Re-configure to save learned information.
-  configure_file(
-    ${CMAKE_ROOT}/Modules/CMakeCCompiler.cmake.in
-    ${CMAKE_PLATFORM_INFO_DIR}/CMakeCCompiler.cmake
-    @ONLY
-    )
-  include(${CMAKE_PLATFORM_INFO_DIR}/CMakeCCompiler.cmake)
+# Re-configure to save learned information.
+configure_file(
+  ${CMAKE_ROOT}/Modules/CMakeCCompiler.cmake.in
+  ${CMAKE_PLATFORM_INFO_DIR}/CMakeCCompiler.cmake
+  @ONLY
+  )
+include(${CMAKE_PLATFORM_INFO_DIR}/CMakeCCompiler.cmake)
 
-  if(CMAKE_C_SIZEOF_DATA_PTR)
-    foreach(f ${CMAKE_C_ABI_FILES})
-      include(${f})
-    endforeach()
-    unset(CMAKE_C_ABI_FILES)
-  endif()
+if(CMAKE_C_SIZEOF_DATA_PTR)
+  foreach(f ${CMAKE_C_ABI_FILES})
+    include(${f})
+  endforeach()
+  unset(CMAKE_C_ABI_FILES)
 endif()
 
 set(CMAKE_TRY_COMPILE_TARGET_TYPE ${__CMAKE_SAVED_TRY_COMPILE_TARGET_TYPE})