[flang][nfc] Move `external-hello-world` to flang/examples

As `external-hello-world` is not really a test, I am moving it from
`flang/unittest/Runtime` to `flang/examples` (it makes a lot of sense as
an example). I've not modified the source code (apart from adjusting the
include paths).

Differential Revision: https://reviews.llvm.org/D104320

2 files changed, 59 insertions, 0 deletions

diff --git a/flang/examples/CMakeLists.txt b/flang/examples/CMakeLists.txt
new file mode 100644
index 000000000000..3ca9feddf33e
--- /dev/null
+++ b/flang/examples/CMakeLists.txt
@@ -0,0 +1,8 @@
+# This test is not run by default as it requires input.
+add_executable(external-hello-world
+  external-hello.cpp
+)
+
+target_link_libraries(external-hello-world
+  FortranRuntime
+)
diff --git a/flang/examples/external-hello.cpp b/flang/examples/external-hello.cpp
new file mode 100644
index 000000000000..7c300d702cae
--- /dev/null
+++ b/flang/examples/external-hello.cpp
@@ -0,0 +1,51 @@
+#include "../runtime/io-api.h"
+#include "../runtime/main.h"
+#include "../runtime/stop.h"
+#include <cstring>
+#include <limits>
+
+using namespace Fortran::runtime::io;
+
+void output1() {
+  auto io{IONAME(BeginExternalListOutput)()};
+  const char str[]{"Hello, world!"};
+  IONAME(OutputAscii)(io, str, std::strlen(str));
+  IONAME(OutputInteger64)(io, 678);
+  IONAME(OutputReal64)(io, 0.0);
+  IONAME(OutputReal64)(io, 2.0 / 3.0);
+  IONAME(OutputReal64)(io, 1.0e99);
+  IONAME(OutputReal64)(io, std::numeric_limits<double>::infinity());
+  IONAME(OutputReal64)(io, -std::numeric_limits<double>::infinity());
+  IONAME(OutputReal64)(io, std::numeric_limits<double>::quiet_NaN());
+  IONAME(OutputComplex64)(io, 123.0, -234.0);
+  IONAME(OutputLogical)(io, false);
+  IONAME(OutputLogical)(io, true);
+  IONAME(EndIoStatement)(io);
+}
+
+void input1() {
+  auto io{IONAME(BeginExternalListOutput)()};
+  const char prompt[]{"Enter an integer value:"};
+  IONAME(OutputAscii)(io, prompt, std::strlen(prompt));
+  IONAME(EndIoStatement)(io);
+
+  io = IONAME(BeginExternalListInput)();
+  std::int64_t n{-666};
+  IONAME(InputInteger)(io, n);
+  IONAME(EndIoStatement)(io);
+
+  io = IONAME(BeginExternalListOutput)();
+  const char str[]{"Result:"};
+  IONAME(OutputAscii)(io, str, std::strlen(str));
+  IONAME(OutputInteger64)(io, n);
+  IONAME(EndIoStatement)(io);
+}
+
+int main(int argc, const char *argv[], const char *envp[]) {
+  RTNAME(ProgramStart)(argc, argv, envp);
+  output1();
+  input1();
+  RTNAME(PauseStatement)();
+  RTNAME(ProgramEndStatement)();
+  return 0;
+}