From 2b2595e03d328f8c49afe55f765635c03dc81865 Mon Sep 17 00:00:00 2001
From: Tamar Christina <tamar@zhox.com>
Date: Mon, 25 Sep 2017 20:21:39 +0100
Subject: [PATCH] Ensure text mode when calling debug functions

Summary:
Something seems to be changing stderr into binary mode,
so when the `traceIO` is called, the C code that ultimately
calls `vfprintf` is using a binary mode handle.

This causes newlines not to be encoded properly.

The patch ensures we're in text mode when writing the debug
messages (% interleaving as it's not thread safe at all) and restores
the previous mode when done.

I'm slightly concerned about the performance implications of writing
large dumps out in text mode, but I think the current behavior is not
intended as I cannot see any of the printing code setting the mode of
the std handles.

Test Plan: ./validate

Reviewers: austin, bgamari, erikd, simonmar

Reviewed By: bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #14188

Differential Revision: https://phabricator.haskell.org/D4018
---
 rts/RtsMessages.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/rts/RtsMessages.c b/rts/RtsMessages.c
index 0859e5093b..5782c0dadb 100644
--- a/rts/RtsMessages.c
+++ b/rts/RtsMessages.c
@@ -21,6 +21,7 @@
 
 #if defined(HAVE_WINDOWS_H)
 #include <windows.h>
+#include <fcntl.h>
 #endif
 
 /* -----------------------------------------------------------------------------
@@ -137,7 +138,9 @@ isGUIApp(void)
 void GNU_ATTRIBUTE(__noreturn__)
 rtsFatalInternalErrorFn(const char *s, va_list ap)
 {
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
+  /* Ensure we're in text mode so newlines get encoded properly.  */
+  int mode = _setmode (_fileno(stderr), _O_TEXT);
   if (isGUIApp())
   {
      char title[BUFSIZE], message[BUFSIZE];
@@ -174,6 +177,9 @@ rtsFatalInternalErrorFn(const char *s, va_list ap)
      fprintf(stderr, "    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug\n");
      fflush(stderr);
   }
+#if defined(mingw32_HOST_OS)
+  _setmode (_fileno(stderr), mode);
+#endif
 
 #if defined(TRACING)
   if (RtsFlags.TraceFlags.tracing == TRACE_EVENTLOG) endEventLogging();
@@ -186,7 +192,9 @@ rtsFatalInternalErrorFn(const char *s, va_list ap)
 void
 rtsErrorMsgFn(const char *s, va_list ap)
 {
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
+  /* Ensure we're in text mode so newlines get encoded properly.  */
+  int mode = _setmode (_fileno(stderr), _O_TEXT);
   if (isGUIApp())
   {
      char buf[BUFSIZE];
@@ -211,6 +219,9 @@ rtsErrorMsgFn(const char *s, va_list ap)
      vfprintf(stderr, s, ap);
      fprintf(stderr, "\n");
   }
+#if defined(mingw32_HOST_OS)
+  _setmode (_fileno(stderr), mode);
+#endif
 }
 
 void
@@ -218,7 +229,9 @@ rtsSysErrorMsgFn(const char *s, va_list ap)
 {
     char *syserr;
 
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
+    /* Ensure we're in text mode so newlines get encoded properly.  */
+    int mode = _setmode (_fileno(stderr), _O_TEXT);
     FormatMessage(
         FORMAT_MESSAGE_ALLOCATE_BUFFER |
         FORMAT_MESSAGE_FROM_SYSTEM |
@@ -257,7 +270,7 @@ rtsSysErrorMsgFn(const char *s, va_list ap)
         }
         vfprintf(stderr, s, ap);
         if (syserr) {
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
             // Win32 error messages have a terminating \n
             fprintf(stderr, ": %s", syserr);
 #else
@@ -268,15 +281,18 @@ rtsSysErrorMsgFn(const char *s, va_list ap)
         }
     }
 
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
     if (syserr) LocalFree(syserr);
+    _setmode (_fileno(stderr), mode);
 #endif
 }
 
 void
 rtsDebugMsgFn(const char *s, va_list ap)
 {
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
+  /* Ensure we're in text mode so newlines get encoded properly.  */
+  int mode = _setmode (_fileno(stderr), _O_TEXT);
   if (isGUIApp())
   {
      char buf[BUFSIZE];
@@ -294,4 +310,7 @@ rtsDebugMsgFn(const char *s, va_list ap)
      vfprintf(stderr, s, ap);
      fflush(stderr);
   }
+#if defined(mingw32_HOST_OS)
+  _setmode (_fileno(stderr), mode);
+#endif
 }
-- 
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