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

1 files changed, 22 insertions, 44 deletions

diff --git a/gdb/target/waitstatus.c b/gdb/target/waitstatus.c
index 2293d83..a7209e3 100644
--- a/gdb/target/waitstatus.c
+++ b/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",
-			    kind_str, this->exit_status ());
+    case TARGET_WAITKIND_THREAD_EXITED:
+      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",
-			    kind_str,
-			    gdb_signal_to_symbol_string (this->sig ()));
-
-    case TARGET_WAITKIND_LOADED:
-      return string_printf ("%sloaded", kind_str);
+      return string_appendf (str, ", sig = %s",
+			     gdb_signal_to_symbol_string (this->sig ()));
 
     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,
-			    this->child_ptid ().to_string ().c_str ());
+      return string_appendf (str, ", child_ptid = %s",
+			     this->child_ptid ().to_string ().c_str ());
 
     case TARGET_WAITKIND_EXECD:
-      return string_printf ("%sexecd, execd_pathname = %s", kind_str,
-			    this->execd_pathname ());
+      return string_appendf (str, ", execd_pathname = %s",
+			     this->execd_pathname ());
 
+    case TARGET_WAITKIND_LOADED:
     case TARGET_WAITKIND_VFORK_DONE:
-      return string_printf ("%svfork-done", kind_str);
-
+    case TARGET_WAITKIND_SPURIOUS:
     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_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);
-
-    case TARGET_WAITKIND_THREAD_EXITED:
-      return string_printf ("%sthread exited, status = %d",
-			    kind_str, this->exit_status ());
-
-    default:
-      return string_printf ("%sunknown???", kind_str);
+      return str;
     }
+#pragma GCC diagnostic pop
+
+  gdb_assert_not_reached ("invalid target_waitkind value: %d",
+			  (int) this->kind ());
 }