gdb: introduce target_waitkind_str, use it in target_waitstatus::to_string

I would like to print target_waitkind values in debug messages, so I
think that a target_waitkind-to-string function would be useful.  While
at it, use it in target_waitstatus::to_string.  This changes the output
of target_waitstatus::to_string a bit, but I think it is for the better.
The debug messages will show a string matching exactly the
target_waitkind enumerator (minus the TARGET_WAITKIND prefix).

As a convenience, make string_appendf return the same reference to
string it got as a parameter.  This allows doing this:

  return string_appendf (str, "foo");

... keeping the code concise.

Change-Id: I383dffc9c78614e7d0668b1516073905e798eef7

gdb/target/waitstatus.c

@@ -20,73 +20,51 @@
 #include "gdbsupport/common-defs.h"
 #include "waitstatus.h"
 
-/* Return a pretty printed form of target_waitstatus.  */
+/* See waitstatus.h.  */
 
 std::string
 target_waitstatus::to_string () const
 {
-  const char *kind_str = "status->kind = ";
+  std::string str = string_printf
+    ("status->kind = %s", target_waitkind_str (this->kind ()));
 
+/* Make sure the compiler warns if a new TARGET_WAITKIND enumerator is added
+   but not handled here.  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic error "-Wswitch"
   switch (this->kind ())
     {
     case TARGET_WAITKIND_EXITED:
-      return string_printf ("%sexited, status = %d",
+    case TARGET_WAITKIND_THREAD_EXITED:
-			    kind_str, this->exit_status ());
+      return string_appendf (str, ", exit_status = %d", this->exit_status ());
 
     case TARGET_WAITKIND_STOPPED:
-      return string_printf ("%sstopped, signal = %s",
-			    kind_str,
-			    gdb_signal_to_symbol_string (this->sig ()));
-
     case TARGET_WAITKIND_SIGNALLED:
-      return string_printf ("%ssignalled, signal = %s",
+      return string_appendf (str, ", sig = %s",
-			    kind_str,
+			     gdb_signal_to_symbol_string (this->sig ()));
-			    gdb_signal_to_symbol_string (this->sig ()));
-
-    case TARGET_WAITKIND_LOADED:
-      return string_printf ("%sloaded", kind_str);
 
     case TARGET_WAITKIND_FORKED:
-      return string_printf ("%sforked, child_ptid = %s", kind_str,
-			    this->child_ptid ().to_string ().c_str ());
-
     case TARGET_WAITKIND_VFORKED:
-      return string_printf ("%svforked, child_ptid = %s", kind_str,
+      return string_appendf (str, ", child_ptid = %s",
-			    this->child_ptid ().to_string ().c_str ());
+			     this->child_ptid ().to_string ().c_str ());
 
     case TARGET_WAITKIND_EXECD:
-      return string_printf ("%sexecd, execd_pathname = %s", kind_str,
+      return string_appendf (str, ", execd_pathname = %s",
-			    this->execd_pathname ());
+			     this->execd_pathname ());
 
+    case TARGET_WAITKIND_LOADED:
     case TARGET_WAITKIND_VFORK_DONE:
-      return string_printf ("%svfork-done", kind_str);
-
-    case TARGET_WAITKIND_SYSCALL_ENTRY:
-      return string_printf ("%sentered syscall", kind_str);
-
-    case TARGET_WAITKIND_SYSCALL_RETURN:
-      return string_printf ("%sexited syscall", kind_str);
-
     case TARGET_WAITKIND_SPURIOUS:
-      return string_printf ("%sspurious", kind_str);
+    case TARGET_WAITKIND_SYSCALL_ENTRY:
-
+    case TARGET_WAITKIND_SYSCALL_RETURN:
     case TARGET_WAITKIND_IGNORE:
-      return string_printf ("%signore", kind_str);
-
     case TARGET_WAITKIND_NO_HISTORY:
-      return string_printf ("%sno-history", kind_str);
-
     case TARGET_WAITKIND_NO_RESUMED:
-      return string_printf ("%sno-resumed", kind_str);
-
     case TARGET_WAITKIND_THREAD_CREATED:
-      return string_printf ("%sthread created", kind_str);
+      return str;
-
-    case TARGET_WAITKIND_THREAD_EXITED:
-      return string_printf ("%sthread exited, status = %d",
-			    kind_str, this->exit_status ());
-
-    default:
-      return string_printf ("%sunknown???", kind_str);
     }
+#pragma GCC diagnostic pop
+
+  gdb_assert_not_reached ("invalid target_waitkind value: %d",
+			  (int) this->kind ());
 }

gdb/target/waitstatus.h

@@ -101,6 +101,55 @@ enum target_waitkind
   TARGET_WAITKIND_THREAD_EXITED,
 };
 
+/* Return KIND as a string.  */
+
+static inline const char *
+target_waitkind_str (target_waitkind kind)
+{
+/* Make sure the compiler warns if a new TARGET_WAITKIND enumerator is added
+   but not handled here.  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic error "-Wswitch"
+  switch (kind)
+  {
+    case TARGET_WAITKIND_EXITED:
+      return "EXITED";
+    case TARGET_WAITKIND_STOPPED:
+      return "STOPPED";
+    case TARGET_WAITKIND_SIGNALLED:
+      return "SIGNALLED";
+    case TARGET_WAITKIND_LOADED:
+      return "LOADED";
+    case TARGET_WAITKIND_FORKED:
+      return "FORKED";
+    case TARGET_WAITKIND_VFORKED:
+      return "VFORKED";
+    case TARGET_WAITKIND_EXECD:
+      return "EXECD";
+    case TARGET_WAITKIND_VFORK_DONE:
+      return "VFORK_DONE";
+    case TARGET_WAITKIND_SYSCALL_ENTRY:
+      return "SYSCALL_ENTRY";
+    case TARGET_WAITKIND_SYSCALL_RETURN:
+      return "SYSCALL_RETURN";
+    case TARGET_WAITKIND_SPURIOUS:
+      return "SPURIOUS";
+    case TARGET_WAITKIND_IGNORE:
+      return "IGNORE";
+    case TARGET_WAITKIND_NO_HISTORY:
+      return "NO_HISTORY";
+    case TARGET_WAITKIND_NO_RESUMED:
+      return "NO_RESUMED";
+    case TARGET_WAITKIND_THREAD_CREATED:
+      return "THREAD_CREATED";
+    case TARGET_WAITKIND_THREAD_EXITED:
+      return "THREAD_EXITED";
+  };
+#pragma GCC diagnostic pop
+
+  gdb_assert_not_reached ("invalid target_waitkind value: %d\n", (int) kind);
+}
+
 struct target_waitstatus
 {
   /* Default constructor.  */

gdb/unittests/common-utils-selftests.c

@@ -80,7 +80,8 @@ string_vprintf_tests ()
 /* Type of both 'string_appendf' and the 'string_vappendf_wrapper'
    function below.  Used to run the same tests against both
    string_appendf and string_vappendf.  */
-typedef void (string_appendf_func) (std::string &str, const char *fmt, ...)
+typedef std::string &(string_appendf_func) (std::string &str, const char *fmt,
+					    ...)
   ATTRIBUTE_PRINTF (2, 3);
 
 static void
@@ -101,7 +102,7 @@ test_appendf_func (string_appendf_func *func)
   SELF_CHECK (str == "test23foo 45 bar");
 }
 
-static void ATTRIBUTE_PRINTF (2, 3)
+static std::string & ATTRIBUTE_PRINTF (2, 3)
 string_vappendf_wrapper (std::string &str, const char *fmt, ...)
 {
   va_list vp;
@@ -109,6 +110,8 @@ string_vappendf_wrapper (std::string &str, const char *fmt, ...)
   va_start (vp, fmt);
   string_vappendf (str, fmt, vp);
   va_end (vp);
+
+  return str;
 }
 
 static void

gdbsupport/common-utils.cc

@@ -119,7 +119,7 @@ string_vprintf (const char* fmt, va_list args)
 
 /* See documentation in common-utils.h.  */
 
-void
+std::string &
 string_appendf (std::string &str, const char *fmt, ...)
 {
   va_list vp;
@@ -127,12 +127,14 @@ string_appendf (std::string &str, const char *fmt, ...)
   va_start (vp, fmt);
   string_vappendf (str, fmt, vp);
   va_end (vp);
+
+  return str;
 }
 
 
 /* See documentation in common-utils.h.  */
 
-void
+std::string &
 string_vappendf (std::string &str, const char *fmt, va_list args)
 {
   va_list vp;
@@ -148,6 +150,8 @@ string_vappendf (std::string &str, const char *fmt, va_list args)
   /* C++11 and later guarantee std::string uses contiguous memory and
      always includes the terminating '\0'.  */
   vsprintf (&str[curr_size], fmt, args); /* ARI: vsprintf */
+
+  return str;
 }
 
 char *

gdbsupport/common-utils.h

@@ -54,11 +54,11 @@ std::string string_vprintf (const char* fmt, va_list args)
 
 /* Like string_printf, but appends to DEST instead of returning a new
    std::string.  */
-void string_appendf (std::string &dest, const char* fmt, ...)
+std::string &string_appendf (std::string &dest, const char* fmt, ...)
   ATTRIBUTE_PRINTF (2, 3);
 
 /* Like string_appendf, but takes a va_list.  */
-void string_vappendf (std::string &dest, const char* fmt, va_list args)
+std::string &string_vappendf (std::string &dest, const char* fmt, va_list args)
   ATTRIBUTE_PRINTF (2, 0);
 
 /* Make a copy of the string at PTR with LEN characters