CTest: Restore inheritance of stdin by test processes

Since commit v3.11.0-rc1~117^2 (CTest: Re-implement test process
handling using libuv, 2017-12-10) we do not give the child test
processes any stdin.  Prior to that change we let the child test
processes inherit stdin from ctest itself.  Tests that run serially
might be able to use the real stdin meaningfully, so restore that
behavior and add a test case.

Fixes: #18591

6 files changed, 36 insertions, 2 deletions

diff --git a/Source/CTest/cmProcess.cxx b/Source/CTest/cmProcess.cxx
index 39cea87958..c4cf046cf6 100644
--- a/Source/CTest/cmProcess.cxx
+++ b/Source/CTest/cmProcess.cxx
@@ -127,7 +127,8 @@ bool cmProcess::StartProcess(uv_loop_t& loop, std::vector<size_t>* affinity)
   uv_pipe_open(pipe_writer, fds[1]);
 
   uv_stdio_container_t stdio[3];
-  stdio[0].flags = UV_IGNORE;
+  stdio[0].flags = UV_INHERIT_FD;
+  stdio[0].data.fd = 0;
   stdio[1].flags = UV_INHERIT_STREAM;
   stdio[1].data.stream = pipe_writer;
   stdio[2] = stdio[1];
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index ecd4441672..99f4ae7f4e 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -368,7 +368,8 @@ add_RunCMake_test(FetchContent)
 if(NOT CMake_TEST_EXTERNAL_CMAKE)
   set(CTestCommandLine_ARGS -DTEST_AFFINITY=$<TARGET_FILE:testAffinity>)
 endif()
-add_RunCMake_test(CTestCommandLine)
+add_executable(print_stdin print_stdin.c)
+add_RunCMake_test(CTestCommandLine -DTEST_PRINT_STDIN=$<TARGET_FILE:print_stdin>)
 add_RunCMake_test(CacheNewline)
 # Only run this test on unix platforms that support
 # symbolic links
diff --git a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
index 9e8d050a5e..750ae5026b 100644
--- a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
@@ -161,3 +161,15 @@ endfunction()
 if(TEST_AFFINITY)
   run_TestAffinity()
 endif()
+
+function(run_TestStdin)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/TestStdin)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+  file(WRITE "${RunCMake_TEST_BINARY_DIR}/CTestTestfile.cmake" "
+  add_test(TestStdin \"${TEST_PRINT_STDIN}\")
+  ")
+  run_cmake_command(TestStdin ${CMAKE_CTEST_COMMAND} -V)
+endfunction()
+run_TestStdin()
diff --git a/Tests/RunCMake/CTestCommandLine/TestStdin-stdin.txt b/Tests/RunCMake/CTestCommandLine/TestStdin-stdin.txt
new file mode 100644
index 0000000000..d83b50a687
--- /dev/null
+++ b/Tests/RunCMake/CTestCommandLine/TestStdin-stdin.txt
@@ -0,0 +1 @@
+Content for TestStdin
diff --git a/Tests/RunCMake/CTestCommandLine/TestStdin-stdout.txt b/Tests/RunCMake/CTestCommandLine/TestStdin-stdout.txt
new file mode 100644
index 0000000000..d83b50a687
--- /dev/null
+++ b/Tests/RunCMake/CTestCommandLine/TestStdin-stdout.txt
@@ -0,0 +1 @@
+Content for TestStdin
diff --git a/Tests/RunCMake/print_stdin.c b/Tests/RunCMake/print_stdin.c
new file mode 100644
index 0000000000..e083e6297e
--- /dev/null
+++ b/Tests/RunCMake/print_stdin.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+
+int main()
+{
+  char buf[1024];
+  size_t nIn = sizeof(buf);
+  while (nIn == sizeof(buf)) {
+    nIn = fread(buf, 1, sizeof(buf), stdin);
+    if (nIn > 0) {
+      size_t nOut;
+      nOut = fwrite(buf, 1, nIn, stdout);
+      if (nOut != nIn) {
+        return 1;
+      }
+    }
+  }
+  return 0;
+}