patch 8.1.2149: crash when running out of memory very early

Problem:    Crash when running out of memory very early.
Solution:   Do not use IObuff when it's NULL. (closes #5052)

src/message.c

@@ -355,6 +355,14 @@ int vim_snprintf(char *str, size_t str_m, const char *fmt, ...);
 
     int
 smsg(const char *s, ...)
+{
+    if (IObuff == NULL)
+    {
+	// Very early in initialisation and already something wrong, just
+	// give the raw message so the user at least gets a hint.
+	return msg((char *)s);
+    }
+    else
     {
 	va_list arglist;
 
@@ -363,9 +371,18 @@ smsg(const char *s, ...)
 	va_end(arglist);
 	return msg((char *)IObuff);
     }
+}
 
     int
 smsg_attr(int attr, const char *s, ...)
+{
+    if (IObuff == NULL)
+    {
+	// Very early in initialisation and already something wrong, just
+	// give the raw message so the user at least gets a hint.
+	return msg_attr((char *)s, attr);
+    }
+    else
     {
 	va_list arglist;
 
@@ -374,9 +391,18 @@ smsg_attr(int attr, const char *s, ...)
 	va_end(arglist);
 	return msg_attr((char *)IObuff, attr);
     }
+}
 
     int
 smsg_attr_keep(int attr, const char *s, ...)
+{
+    if (IObuff == NULL)
+    {
+	// Very early in initialisation and already something wrong, just
+	// give the raw message so the user at least gets a hint.
+	return msg_attr_keep((char *)s, attr, TRUE);
+    }
+    else
     {
 	va_list arglist;
 
@@ -385,6 +411,7 @@ smsg_attr_keep(int attr, const char *s, ...)
 	va_end(arglist);
 	return msg_attr_keep((char *)IObuff, attr, TRUE);
     }
+}
 
 #endif
 
@@ -723,8 +750,16 @@ emsg(char *s)
     int
 semsg(const char *s, ...)
 {
-    /* Skip this if not giving error messages at the moment. */
+    // Skip this if not giving error messages at the moment.
     if (!emsg_not_now())
+    {
+	if (IObuff == NULL)
+	{
+	    // Very early in initialisation and already something wrong, just
+	    // give the raw message so the user at least gets a hint.
+	    return emsg_core((char_u *)s);
+	}
+	else
 	{
 	    va_list ap;
 
@@ -733,7 +768,8 @@ semsg(const char *s, ...)
 	    va_end(ap);
 	    return emsg_core(IObuff);
 	}
-    return TRUE;		/* no error messages at the moment */
+    }
+    return TRUE;		// no error messages at the moment
 }
 #endif
 
@@ -763,6 +799,14 @@ iemsg(char *s)
 siemsg(const char *s, ...)
 {
     if (!emsg_not_now())
+    {
+	if (IObuff == NULL)
+	{
+	    // Very early in initialisation and already something wrong, just
+	    // give the raw message so the user at least gets a hint.
+	    emsg_core((char_u *)s);
+	}
+	else
 	{
 	    va_list ap;
 
@@ -771,6 +815,7 @@ siemsg(const char *s, ...)
 	    va_end(ap);
 	    emsg_core(IObuff);
 	}
+    }
 # ifdef ABORT_ON_INTERNAL_ERROR
     abort();
 # endif
@@ -3505,10 +3550,19 @@ give_warning(char_u *message, int hl)
 #if defined(FEAT_EVAL) || defined(PROTO)
     void
 give_warning2(char_u *message, char_u *a1, int hl)
+{
+    if (IObuff == NULL)
+    {
+	// Very early in initialisation and already something wrong, just give
+	// the raw message so the user at least gets a hint.
+	give_warning((char_u *)message, hl);
+    }
+    else
     {
 	vim_snprintf((char *)IObuff, IOSIZE, (char *)message, a1);
 	give_warning(IObuff, hl);
     }
+}
 #endif
 
 /*

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2149,
 /**/
     2148,
 /**/