try_compile: Pass linker flags into test project (#14066)

Copy CMAKE_EXE_LINKER_FLAGS into the test project generated by
try_compile, just like we already copy CMAKE_<LANG>_FLAGS.

Add CMake Policy CMP0056 to activate this behavior in a compatible way,
but do not warn by default when the policy is not set since it will
affect all try_compile calls.

Extend the RunCMake.try_compile test with a case covering this behavior
for each policy setting.

4 files changed, 86 insertions, 0 deletions

diff --git a/Tests/RunCMake/try_compile/CMP0056-stderr.txt b/Tests/RunCMake/try_compile/CMP0056-stderr.txt
new file mode 100644
index 0000000..5c1f0e4
--- /dev/null
+++ b/Tests/RunCMake/try_compile/CMP0056-stderr.txt
@@ -0,0 +1,13 @@
+before try_compile with CMP0056 WARN-default
+after try_compile with CMP0056 WARN-default
+*
+CMake Warning \(dev\) at CMP0056.cmake:[0-9]+ \(try_compile\):
+  Policy CMP0056 is not set: Honor link flags in try_compile\(\) source-file
+  signature.  Run "cmake --help-policy CMP0056" for policy details.  Use the
+  cmake_policy command to set the policy and suppress this warning.
+
+  For compatibility with older versions of CMake, try_compile is not honoring
+  caller link flags \(e.g.  CMAKE_EXE_LINKER_FLAGS\) in the test project.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.$
diff --git a/Tests/RunCMake/try_compile/CMP0056-stdout.txt b/Tests/RunCMake/try_compile/CMP0056-stdout.txt
new file mode 100644
index 0000000..89e7c43
--- /dev/null
+++ b/Tests/RunCMake/try_compile/CMP0056-stdout.txt
@@ -0,0 +1,4 @@
+-- try_compile with CMP0056 WARN-default worked as expected
+-- try_compile with CMP0056 WARN-enabled worked as expected
+-- try_compile with CMP0056 OLD worked as expected
+-- try_compile with CMP0056 NEW worked as expected
diff --git a/Tests/RunCMake/try_compile/CMP0056.cmake b/Tests/RunCMake/try_compile/CMP0056.cmake
new file mode 100644
index 0000000..e8d3d4a
--- /dev/null
+++ b/Tests/RunCMake/try_compile/CMP0056.cmake
@@ -0,0 +1,67 @@
+enable_language(C)
+set(obj "${CMAKE_C_OUTPUT_EXTENSION}")
+if(BORLAND)
+  set(pre -)
+endif()
+set(CMAKE_EXE_LINKER_FLAGS ${pre}BADFLAG${obj})
+
+#-----------------------------------------------------------------------------
+message("before try_compile with CMP0056 WARN-default")
+try_compile(RESULT ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}/src.c
+  OUTPUT_VARIABLE out
+  )
+string(REPLACE "\n" "\n  " out "  ${out}")
+if(NOT RESULT)
+  message(FATAL_ERROR "try_compile failed but should have passed:\n${out}")
+elseif("x${out}" MATCHES "BADFLAG")
+  message(FATAL_ERROR "try_compile output mentions BADFLAG:\n${out}")
+else()
+  message(STATUS "try_compile with CMP0056 WARN-default worked as expected")
+endif()
+message("after try_compile with CMP0056 WARN-default")
+
+#-----------------------------------------------------------------------------
+set(CMAKE_POLICY_WARNING_CMP0056 ON)
+try_compile(RESULT ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}/src.c
+  OUTPUT_VARIABLE out
+  )
+string(REPLACE "\n" "\n  " out "  ${out}")
+if(NOT RESULT)
+  message(FATAL_ERROR "try_compile failed but should have passed:\n${out}")
+elseif("x${out}" MATCHES "BADFLAG")
+  message(FATAL_ERROR "try_compile output mentions BADFLAG:\n${out}")
+else()
+  message(STATUS "try_compile with CMP0056 WARN-enabled worked as expected")
+endif()
+
+#-----------------------------------------------------------------------------
+cmake_policy(SET CMP0056 OLD)
+try_compile(RESULT ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}/src.c
+  OUTPUT_VARIABLE out
+  )
+string(REPLACE "\n" "\n  " out "  ${out}")
+if(NOT RESULT)
+  message(FATAL_ERROR "try_compile failed but should have passed:\n${out}")
+elseif("x${out}" MATCHES "BADFLAG")
+  message(FATAL_ERROR "try_compile output mentions BADFLAG:\n${out}")
+else()
+  message(STATUS "try_compile with CMP0056 OLD worked as expected")
+endif()
+
+#-----------------------------------------------------------------------------
+cmake_policy(SET CMP0056 NEW)
+try_compile(RESULT ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}/src.c
+  OUTPUT_VARIABLE out
+  )
+string(REPLACE "\n" "\n  " out "  ${out}")
+if(RESULT)
+  message(FATAL_ERROR "try_compile passed but should have failed:\n${out}")
+elseif(NOT "x${out}" MATCHES "BADFLAG")
+  message(FATAL_ERROR "try_compile did not fail with BADFLAG:\n${out}")
+else()
+  message(STATUS "try_compile with CMP0056 NEW worked as expected")
+endif()
diff --git a/Tests/RunCMake/try_compile/RunCMakeTest.cmake b/Tests/RunCMake/try_compile/RunCMakeTest.cmake
index c934458..06096b2 100644
--- a/Tests/RunCMake/try_compile/RunCMakeTest.cmake
+++ b/Tests/RunCMake/try_compile/RunCMakeTest.cmake
@@ -15,3 +15,5 @@ run_cmake(BadSources1)
 run_cmake(BadSources2)
 run_cmake(NonSourceCopyFile)
 run_cmake(NonSourceCompileDefinitions)
+
+run_cmake(CMP0056)