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

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

https://gcc.gnu.org/g:98806df7833841ec0b748d3a3e98f98fbdd97a39

commit 98806df7833841ec0b748d3a3e98f98fbdd97a39
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Wed Mar 24 22:11:10 2021 +0100

    Fix hello world with std.stdio

Diff:
---
 libphobos/libdruntime/config/mingw/msvc.c |  34 +++++-----
 libphobos/libdruntime/core/stdc/stdio.d   | 108 +++++++++++++++++++++++++++---
 2 files changed, 117 insertions(+), 25 deletions(-)

diff --git a/libphobos/libdruntime/config/mingw/msvc.c b/libphobos/libdruntime/config/mingw/msvc.c
index 25b15a06950..4ca77e58f5a 100644
--- a/libphobos/libdruntime/config/mingw/msvc.c
+++ b/libphobos/libdruntime/config/mingw/msvc.c
@@ -23,32 +23,32 @@ a copy of the GCC Runtime Library Exception along with this program;
 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 <http://www.gnu.org/licenses/>.  */
 
+#ifdef __MINGW32__
+#include <_mingw.h>
+#endif
 #include <stdio.h>
 
-/* 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;
+/* The D runtime library defines stdin, stdout, and stderr as extern(C) symbols
+   in the core.stdc.stdio module, and require initializing at start-up.  */
+__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.  */
+/* Set to 1 if runtime is using libucrt.dll.  */
 unsigned char msvcUsesUCRT;
 
 void init_msvc()
 {
-#if __MSVCRT_VERSION__ >= 0x1400
+  core_stdc_stdin = stdin;
+  core_stdc_stdout = stdout;
+  core_stdc_stderr = stderr;
+
+#if __MSVCRT_VERSION__ >= 0xE00
   msvcUsedUCRT = 1;
 #endif
-
-  stdin = c_stdin;
-  stdout = c_stdout;
-  stderr = c_stderr;
 }
diff --git a/libphobos/libdruntime/core/stdc/stdio.d b/libphobos/libdruntime/core/stdc/stdio.d
index 532a0803f55..c4dce71f1e0 100644
--- a/libphobos/libdruntime/core/stdc/stdio.d
+++ b/libphobos/libdruntime/core/stdc/stdio.d
@@ -391,7 +391,21 @@ else version (CRuntime_Microsoft)
     ///
     struct _iobuf
     {
+      version (MinGW)
+      {
+        char* _ptr;
+        int _cnt;
+        char* _base;
+        int _flag;
+        int _file;
+        int _charbuf;
+        int _bufsiz;
+        char* _tmpfname;
+      }
+      else
+      {
         void* undefined;
+      }
     }
 
     ///
@@ -1347,7 +1361,7 @@ version (CRuntime_DigitalMars)
     ///
     pure int  fileno()(FILE* stream)   { return stream._file; }
   }
-  ///
+    ///
     pragma(printf)
     int   _snprintf(scope char* s, size_t n, scope const char* fmt, scope const ...);
     ///
@@ -1358,6 +1372,25 @@ version (CRuntime_DigitalMars)
     int   _vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
     ///
     alias _vsnprintf vsnprintf;
+
+    //
+    // Digital Mars under-the-hood C I/O functions.
+    //
+
+    ///
+    int _fputc_nlock(int c, FILE* fp);
+    ///
+    int _fputwc_nlock(int c, FILE* fp);
+    ///
+    int _fgetc_nlock(FILE* fp);
+    ///
+    int _fgetwc_nlock(FILE* fp);
+    ///
+    int __fp_lock(FILE* fp);
+    ///
+    void __fp_unlock(FILE* fp);
+    ///
+    int setmode(int fd, int mode);
 }
 else version (CRuntime_Microsoft)
 {
@@ -1373,7 +1406,10 @@ else version (CRuntime_Microsoft)
     ///
     pure int  ferror(FILE* stream);
     ///
-    pure int  fileno(FILE* stream);
+    pure int  _fileno(FILE* stream);
+    ///
+    alias fileno = _fileno;
+
   }
 
   version (MinGW)
@@ -1410,16 +1446,72 @@ else version (CRuntime_Microsoft)
     int  vsnprintf(scope char* s, size_t n, scope const char* format, va_list arg);
   }
 
+    //
+    // Microsoft under-the-hood C I/O functions
+    // Uses _iobuf* for the unshared version of FILE*,
+    // usable when the FILE is locked.
+    //
+
+  version (MinGW)
+  {
+    private int _filbuf(FILE*);
+    private int _flsbuf(int, FILE*);
+
     ///
-    int _fputc_nolock(int c, FILE *fp);
+    int _fputc_nolock()(int c, FILE* fp)
+    {
+        pragma(inline, true);
+        fp._cnt = fp._cnt - 1;
+        if (fp._cnt >= 0)
+        {
+            immutable ch = cast(char)c;
+            *fp._ptr = ch;
+            fp._ptr = fp._ptr + 1;
+            return ch & 0xFF;
+        }
+        else
+            return _flsbuf(c, fp);
+    }
     ///
-    int _fgetc_nolock(FILE *fp);
-
+    int _fgetc_nolock()(FILE* fp)
+    {
+        pragma(inline, true);
+        fp._cnt = fp._cnt - 1;
+        if (fp._cnt >= 0)
+        {
+            immutable ch = *fp._ptr;
+            fp._ptr = fp._ptr + 1;
+            return ch & 0xFF;
+        }
+        else
+            return _filbuf(fp);
+    }
+  }
+  else
+  {
     ///
-    int _lock_file(FILE *fp);
+    int _fputc_nolock(int c, FILE* fp);
     ///
-    int _unlock_file(FILE *fp);
-
+    int _fgetc_nolock(FILE* fp);
+  }
+    ///
+    int _fputwc_nolock(int c, FILE* fp);
+    ///
+    int _fgetwc_nolock(FILE* fp);
+    ///
+    void _lock_file(FILE* fp);
+    ///
+    void _unlock_file(FILE* fp);
+    ///
+    int _setmode(int fd, int mode);
+    ///
+    FILE* _fdopen(int fd, const (char)* mode);
+    ///
+    FILE* _wfdopen(int fd, const (wchar)* mode);
+    ///
+    int _fseeki64(FILE* stream, long offset, int origin);
+    ///
+    long _ftelli64(FILE* stream);
     ///
     intptr_t _get_osfhandle(int fd);
     ///