[flang] Add a wrapper for Fortran main program

[jeanPerier]

Summary

Add a C wrapper that calls the Fortran runtime initialization and
finalization routines as well as the compiled Fortran main program
_QQmain.

Place it in its own library to satisfy shared library builds since it
contains a C main function.

[klausler]

The main program looks okay to me. I can't comment on the cmake mysteries.

[clementval]

flang/runtime/Fortran_main.c

2

Do we need a LLVM header in this file?

[klausler]

flang/runtime/Fortran_main.c

2

Which LLVM headers do you have in mind?

[jeanPerier]

flang/runtime/Fortran_main.c

2

Ah, good catch, I guess it needs the #===-- licence header...

[clementval]

flang/runtime/Fortran_main.c

2

Yah I was thinking about the licence header (with the comments).

[jeanPerier]

Added LLVM licence to Fortran_main.c

[clementval]

LGTM

[jeanPerier]

Does anyone knows why build bots are not running on this patch (only arc lint + unit seems to be done) ?

I pushed the change by accident (arc patched another approved patch on the wrong branch....) and reverted it, but in the meantime I got some windows failure with this patch:

0.181 [141/5/1] Building C object tools\flang\runtime\CMakeFiles\obj.Fortran_main.dir\Fortran_main.c.obj
FAILED: tools/flang/runtime/CMakeFiles/obj.Fortran_main.dir/Fortran_main.c.obj 
C:\PROGRA~2\MICROS~2\2019\COMMUN~1\VC\Tools\MSVC\1429~1.301\bin\Hostx64\x64\cl.exe [...] flang\runtime\Fortran_main.c
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2143: syntax error: missing ')' before '='
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): warning C4431: missing type specifier - int assumed. Note: C no longer supports default-int
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2072: '_FortranAExit': initialization of a function
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2059: syntax error: ')'

So I am wondering how I can make sure I do not break windows here when I find a fix for this.

[clementval]

In D110851#3035731, @jeanPerier wrote:

Does anyone knows why build bots are not running on this patch (only arc lint + unit seems to be done) ?

I pushed the change by accident (arc patched another approved patch on the wrong branch....) and reverted it, but in the meantime I got some windows failure with this patch:

0.181 [141/5/1] Building C object tools\flang\runtime\CMakeFiles\obj.Fortran_main.dir\Fortran_main.c.obj
FAILED: tools/flang/runtime/CMakeFiles/obj.Fortran_main.dir/Fortran_main.c.obj 
C:\PROGRA~2\MICROS~2\2019\COMMUN~1\VC\Tools\MSVC\1429~1.301\bin\Hostx64\x64\cl.exe [...] flang\runtime\Fortran_main.c
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2143: syntax error: missing ')' before '='
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): warning C4431: missing type specifier - int assumed. Note: C no longer supports default-int
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2072: '_FortranAExit': initialization of a function
C:\Users\buildbot-worker\minipc-ryzen-win\flang-x86_64-windows\llvm-project\flang\include\flang/Runtime/stop.h(30): error C2059: syntax error: ')'

So I am wondering how I can make sure I do not break windows here when I find a fix for this.

Might be a config issue. Maybe the path flang/runtime does not trigger a build.

[jeanPerier]

Was added in a better way in https://reviews.llvm.org/D122008.

flang/cmake/modules/AddFlang.cmake

 endmacro()
 
 macro(add_flang_subdirectory name)
   add_llvm_subdirectory(FLANG TOOL ${name})
 endmacro()
 
 macro(add_flang_library name)
   cmake_parse_arguments(ARG
-    "SHARED"
+    "SHARED;STATIC"
     ""
     "ADDITIONAL_HEADERS"
     ${ARGN})
   set(srcs)
   if (MSVC_IDE OR XCODE)
     # Add public headers
     file(RELATIVE_PATH lib_path
       ${FLANG_SOURCE_DIR}/lib/
macro(add_flang_library name)
       
   endif()
 
   if (ARG_SHARED)
     set(LIBTYPE SHARED)
   else()
     # llvm_add_library ignores BUILD_SHARED_LIBS if STATIC is explicitly set,
     # so we need to handle it here.
-    if (BUILD_SHARED_LIBS)
+    if (BUILD_SHARED_LIBS AND NOT ARG_STATIC)
       set(LIBTYPE SHARED OBJECT)
     else()
       set(LIBTYPE STATIC OBJECT)
     endif()
     set_property(GLOBAL APPEND PROPERTY FLANG_STATIC_LIBS ${name})
   endif()
 
   llvm_add_library(${name} ${LIBTYPE} ${ARG_UNPARSED_ARGUMENTS} ${srcs})

flang/runtime/CMakeLists.txt

-#===-- runtime/CMakeLists.txt ----------------------------------------------===#
-#
-# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#
-#===------------------------------------------------------------------------===#
 
 include(CheckCXXSymbolExists)
 include(CheckCXXSourceCompiles)
 check_cxx_symbol_exists(strerror string.h HAVE_STRERROR)
 check_cxx_symbol_exists(strerror_r string.h HAVE_STRERROR_R)
+
 # Can't use symbol exists here as the function is overloaded in C++
 check_cxx_source_compiles(
   "#include <string.h>
    int main() {
      char buf[4096];
      return strerror_s(buf, 4096, 0);
    }
   "
   HAVE_DECL_STRERROR_S)
 
 if (NOT (HAVE_STRERROR OR HAVE_STRERROR_R OR HAVE_DECL_STRERROR_S))
   message(FATAL_ERROR "None of strerror, strerror_r, strerror_s found.")
 endif()
 
 configure_file(config.h.cmake config.h)
 # include_directories is used here instead of target_include_directories
 # because add_flang_library creates multiple objects (STATIC/SHARED, OBJECT)
 # with different names
 include_directories(AFTER ${CMAKE_CURRENT_BINARY_DIR})
 
-add_flang_library(FortranRuntime
+add_flang_library(FortranRuntime PARTIAL_SOURCES_INTENDED
   ISO_Fortran_binding.cpp
   allocatable.cpp
   assign.cpp
   buffer.cpp
   command.cpp
   complex-reduction.c
   copy.cpp
   character.cpp
add_flang_library(FortranRuntime PARTIAL_SOURCES_INTENDED
   type-code.cpp
   type-info.cpp
   unit.cpp
   unit-map.cpp
 
   LINK_LIBS
   FortranDecimal
 )
+
+add_flang_library(Fortran_main STATIC PARTIAL_SOURCES_INTENDED
+  Fortran_main.c
+)

flang/runtime/Fortran_main.c

+//===-- runtime/Fortran_main.c --------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Runtime/main.h"
+#include "flang/Runtime/stop.h"
+
+/* main entry into PROGRAM */
+void _QQmain();
+
+/* C main stub */
+int main(int argc, const char *argv[], const char *envp[])
+{
+  RTNAME(ProgramStart)(argc, argv, envp);
+  _QQmain();
+  RTNAME(ProgramEndStatement)();
+  return 0;
+}