[PATCH v3 3/5] sim: Suppress non-literal printf warning

[Tsukasa OI <research_trasio@irq.a4lg.com>]

Clang generates a warning if the format string of a printf-like function is
not a literal ("-Wformat-nonliteral"). On the default configuration, it
causes a build failure (unless "--disable-werror" is specified).

To avoid this warning, this commit now uses vsnprintf to format error
message and pass the message to sim_engine_abort function with another
printf-style formatting.

This patch is mostly authored by Andrew Burgess and slightly modified by
Tsukasa OI.

Co-authored-by: Andrew Burgess <aburgess@redhat.com>
Signed-off-by: Tsukasa OI <research_trasio@irq.a4lg.com>
---
 sim/common/sim-hw.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/sim/common/sim-hw.c b/sim/common/sim-hw.c
index cece5638bc9..c70770893c9 100644
--- a/sim/common/sim-hw.c
+++ b/sim/common/sim-hw.c
@@ -403,13 +403,16 @@ sim_hw_io_write_buffer (struct sim_state *sd,
 \f
 /* Abort the simulation specifying HW as the reason */
 
-void
+void ATTRIBUTE_PRINTF (2, 0)
 hw_vabort (struct hw *me,
 	   const char *fmt,
 	   va_list ap)
 {
+  int len;
   const char *name;
   char *msg;
+  va_list cpy;
+
   /* find an identity */
   if (me != NULL && hw_path (me) != NULL && hw_path (me) [0] != '\0')
     name = hw_path (me);
@@ -419,16 +422,19 @@ hw_vabort (struct hw *me,
     name = hw_family (me);
   else
     name = "device";
-  /* construct an updated format string */
-  msg = alloca (strlen (name) + strlen (": ") + strlen (fmt) + 1);
-  strcpy (msg, name);
-  strcat (msg, ": ");
-  strcat (msg, fmt);
+
+  /* Expand FMT and AP into MSG buffer.  */
+  va_copy (cpy, ap);
+  len = vsnprintf (NULL, 0, fmt, cpy) + 1;
+  va_end (cpy);
+  msg = alloca (len);
+  vsnprintf (msg, len, fmt, ap);
+
   /* report the problem */
-  sim_engine_vabort (hw_system (me),
-		     STATE_HW (hw_system (me))->cpu,
-		     STATE_HW (hw_system (me))->cia,
-		     msg, ap);
+  sim_engine_abort (hw_system (me),
+		    STATE_HW (hw_system (me))->cpu,
+		    STATE_HW (hw_system (me))->cia,
+		    "%s: %s", name, msg);
 }
 
 void
-- 
2.34.1