ISO C standard as to say about va_list on 7.15 [#3]

       If  access  to  the varying arguments is desired, the called
       function shall declare an object (referred to as ap in  this
       subclause) having type va_list.  The object ap may be passed
       as an argument to another function; if that function invokes
       the  va_arg  macro with parameter ap, the value of ap in the
       calling function is indeterminate and shall be passed to the
       va_end macro prior to any further reference to ap.199)

Which interprets to do reuse a va_list that was already processed.
Instead, use a copy. This fixes crashes on x86-64 and debugging
feasible, since logging is now available. ;-)

1 files changed, 4 insertions, 1 deletions

diff --git a/mdk-stage1/log.c b/mdk-stage1/log.c
index 319079fd7..bb56eb8a3 100644
--- a/mdk-stage1/log.c
+++ b/mdk-stage1/log.c
@@ -37,6 +37,9 @@ static FILE * logfile = NULL;
 
 void vlog_message(const char * s, va_list args)
 {
+	va_list args_copy;
+	va_copy(args_copy, args);
+
 	if (logfile) {
 		fprintf(logfile, "* ");
 		vfprintf(logfile, s, args);
@@ -45,7 +48,7 @@ void vlog_message(const char * s, va_list args)
 	}
 	if (logtty) {
 		fprintf(logtty, "* ");
-		vfprintf(logtty, s, args);
+		vfprintf(logtty, s, args_copy);
 		fprintf(logtty, "\n");
 		fflush(logtty);
 	}