[gcc(refs/users/ibuclaw/heads/mingw)] Fix hello world with std.stdio

[Iain Buclaw <ibuclaw@gcc.gnu.org>]

https://gcc.gnu.org/g:b063aded0533fb19b406f5ca2bec334eb1faded3

commit b063aded0533fb19b406f5ca2bec334eb1faded3
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Wed Mar 24 22:11:10 2021 +0100

    Fix hello world with std.stdio

Diff:
---
 libphobos/configure                       | 74 +++++++++++++++++++++++++++++++
 libphobos/configure.ac                    |  1 +
 libphobos/libdruntime/config/mingw/msvc.c | 21 ++++-----
 libphobos/m4/druntime/libraries.m4        | 14 ++++++
 4 files changed, 98 insertions(+), 12 deletions(-)

diff --git a/libphobos/configure b/libphobos/configure
index fe7cd9c11ff..e483fcd8360 100755
--- a/libphobos/configure
+++ b/libphobos/configure
@@ -15067,6 +15067,80 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 fi
 
 
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+  case "$druntime_cv_target_os" in
+    mingw*)
+      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing _fputc_nolock" >&5
+$as_echo_n "checking for library containing _fputc_nolock... " >&6; }
+if ${ac_cv_search__fputc_nolock+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char _fputc_nolock ();
+int
+main ()
+{
+return _fputc_nolock ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' ucrtbase; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search__fputc_nolock=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search__fputc_nolock+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search__fputc_nolock+:} false; then :
+
+else
+  ac_cv_search__fputc_nolock=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search__fputc_nolock" >&5
+$as_echo "$ac_cv_search__fputc_nolock" >&6; }
+ac_res=$ac_cv_search__fputc_nolock
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+fi
+
+      ;;
+  esac
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+
                             druntime_check_both=no
   ac_fn_c_check_func "$LINENO" "connect" "ac_cv_func_connect"
 if test "x$ac_cv_func_connect" = xyes; then :
diff --git a/libphobos/configure.ac b/libphobos/configure.ac
index 3b5a830cccf..1b1ce5008f0 100644
--- a/libphobos/configure.ac
+++ b/libphobos/configure.ac
@@ -160,6 +160,7 @@ WITH_LOCAL_DRUNTIME([
 DRUNTIME_LIBRARIES_ATOMIC
 DRUNTIME_LIBRARIES_BACKTRACE
 DRUNTIME_LIBRARIES_DLOPEN
+DRUNTIME_LIBRARIES_IO
 DRUNTIME_LIBRARIES_NET
 DRUNTIME_LIBRARIES_UCONTEXT
 DRUNTIME_LIBRARIES_ZLIB
diff --git a/libphobos/libdruntime/config/mingw/msvc.c b/libphobos/libdruntime/config/mingw/msvc.c
index 25b15a06950..85ce3741bca 100644
--- a/libphobos/libdruntime/config/mingw/msvc.c
+++ b/libphobos/libdruntime/config/mingw/msvc.c
@@ -27,17 +27,14 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 /* The symbols for stdin, stdout, and stderr are defined for D in the
    core.stdc.stdio module.  Save the macros and redeclare them here.  */
-#define c_stdin stdin
-#undef stdin
-extern FILE *stdin;
+__attribute__((weakref ("stdin")))
+static FILE *core_stdc_stdin;
 
-#define c_stdout stdout
-#undef stdout
-extern FILE *stdout;
+__attribute__((weakref ("stdout")))
+static FILE *core_stdc_stdout;
 
-#define c_stderr stderr
-#undef stderr
-extern FILE *stderr;
+__attribute__((weakref ("stderr")))
+static FILE *core_stdc_stderr;
 
 /* Set to 1 if run-time is using ucrtbase.dll.  */
 unsigned char msvcUsesUCRT;
@@ -48,7 +45,7 @@ void init_msvc()
   msvcUsedUCRT = 1;
 #endif
 
-  stdin = c_stdin;
-  stdout = c_stdout;
-  stderr = c_stderr;
+  core_stdc_stdin = stdin;
+  core_stdc_stdout = stdout;
+  core_stdc_stderr = stderr;
 }
diff --git a/libphobos/m4/druntime/libraries.m4 b/libphobos/m4/druntime/libraries.m4
index 743d3e3e17c..194602c1bf1 100644
--- a/libphobos/m4/druntime/libraries.m4
+++ b/libphobos/m4/druntime/libraries.m4
@@ -233,3 +233,17 @@ AC_DEFUN([DRUNTIME_LIBRARIES_UCONTEXT],
       AC_MSG_ERROR([swapcontext required but not found]))
   fi
 ])
+
+# DRUNTIME_LIBRARIES_IO
+# -----------------------
+# Autodetect and add IO library to LIBS if necessary.
+AC_DEFUN([DRUNTIME_LIBRARIES_IO],
+[
+  AC_LANG_PUSH([C])
+  case "$druntime_cv_target_os" in
+    mingw*)
+      AC_SEARCH_LIBS([_fputc_nolock], [ucrtbase])
+      ;;
+  esac
+  AC_LANG_POP([C])
+])