Re: [RFC] Never silently discard internal errors

[Daniel Jacobowitz <drow at false dot org>]

On Mon, Sep 25, 2006 at 11:56:35PM -0400, Daniel Jacobowitz wrote:
> On Mon, Sep 25, 2006 at 02:18:38PM -0700, Jim Blandy wrote:
> > 
> > Daniel Jacobowitz <drow@false.org> writes:
> > > On Mon, Sep 25, 2006 at 12:38:40PM -0700, Jim Blandy wrote:
> > >> What if we simply had 'query' itself print out the prompt, followed by
> > >> "[answering 'y', since standard input is not a terminal]" (or
> > >> something more tasteful)?  Then you wouldn't have to go around
> > >> decorating all the calls to query.
> > >
> > > I assume that would be wrong for "set confirm off"?
> > 
> > I don't want to turn this into a bikeshed discussion, but here's what
> > I had in mind:
> 
> Hmm, I like this.  Anyone else?
> 
> [defaulted_query needs similar treatment.]

No one else had an opinion so Jim gets to paint the bikeshed :-)

I've tested and committed the attached.  I took the opportunity to
combine query and defaulted_query, and fix a bug I encountered during
manual testing that could crash GDB if you hit <enter> a couple times
at the prompt.

-- 
Daniel Jacobowitz
CodeSourcery

2006-10-18  Jim Blandy  <jimb@codesourcery.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>

	* utils.c (query): Use defaulted_query.
	(defaulted_query): Handle having no default answer.  Print out
	messages even if we have no terminal.  Prevent memory corruption.

Index: utils.c
===================================================================
RCS file: /cvs/src/src/gdb/utils.c,v
retrieving revision 1.169
diff -u -p -r1.169 utils.c
--- utils.c	21 Sep 2006 13:50:51 -0000	1.169
+++ utils.c	18 Oct 2006 22:14:57 -0000
@@ -1127,92 +1127,13 @@ gdb_print_host_address (const void *addr
 
   fprintf_filtered (stream, "0x%lx", (unsigned long) addr);
 }
-
-/* Ask user a y-or-n question and return 1 iff answer is yes.
-   Takes three args which are given to printf to print the question.
-   The first, a control string, should end in "? ".
-   It should not say how to answer, because we do that.  */
-
-/* VARARGS */
-int
-query (const char *ctlstr, ...)
-{
-  va_list args;
-  int answer;
-  int ans2;
-  int retval;
-
-  /* Automatically answer "yes" if input is not from the user
-     directly, or if the user did not want prompts.  */
-  if (!input_from_terminal_p () || !caution)
-    return 1;
-
-  if (deprecated_query_hook)
-    {
-      va_start (args, ctlstr);
-      return deprecated_query_hook (ctlstr, args);
-    }
-
-  while (1)
-    {
-      wrap_here ("");		/* Flush any buffered output */
-      gdb_flush (gdb_stdout);
-
-      if (annotation_level > 1)
-	printf_filtered (("\n\032\032pre-query\n"));
-
-      va_start (args, ctlstr);
-      vfprintf_filtered (gdb_stdout, ctlstr, args);
-      va_end (args);
-      printf_filtered (_("(y or n) "));
-
-      if (annotation_level > 1)
-	printf_filtered (("\n\032\032query\n"));
-
-      wrap_here ("");
-      gdb_flush (gdb_stdout);
-
-      answer = fgetc (stdin);
-      clearerr (stdin);		/* in case of C-d */
-      if (answer == EOF)	/* C-d */
-	{
-	  retval = 1;
-	  break;
-	}
-      /* Eat rest of input line, to EOF or newline */
-      if (answer != '\n')
-	do
-	  {
-	    ans2 = fgetc (stdin);
-	    clearerr (stdin);
-	  }
-	while (ans2 != EOF && ans2 != '\n' && ans2 != '\r');
-
-      if (answer >= 'a')
-	answer -= 040;
-      if (answer == 'Y')
-	{
-	  retval = 1;
-	  break;
-	}
-      if (answer == 'N')
-	{
-	  retval = 0;
-	  break;
-	}
-      printf_filtered (_("Please answer y or n.\n"));
-    }
-
-  if (annotation_level > 1)
-    printf_filtered (("\n\032\032post-query\n"));
-  return retval;
-}
 
 
-/* This function supports the nquery() and yquery() functions.
+/* This function supports the query, nquery, and yquery functions.
    Ask user a y-or-n question and return 0 if answer is no, 1 if
-   answer is yes, or default the answer to the specified default.
-   DEFCHAR is either 'y' or 'n' and refers to the default answer.
+   answer is yes, or default the answer to the specified default
+   (for yquery or nquery).  DEFCHAR may be 'y' or 'n' to provide a
+   default answer, or '\0' for no default.
    CTLSTR is the control string and should end in "? ".  It should
    not say how to answer, because we do that.
    ARGS are the arguments passed along with the CTLSTR argument to
@@ -1226,10 +1147,18 @@ defaulted_query (const char *ctlstr, con
   int retval;
   int def_value;
   char def_answer, not_def_answer;
-  char *y_string, *n_string;
+  char *y_string, *n_string, *question;
 
   /* Set up according to which answer is the default.  */
-  if (defchar == 'y')
+  if (defchar == '\0')
+    {
+      def_value = 1;
+      def_answer = 'Y';
+      not_def_answer = 'N';
+      y_string = "y";
+      n_string = "n";
+    }
+  else if (defchar == 'y')
     {
       def_value = 1;
       def_answer = 'Y';
@@ -1246,6 +1175,27 @@ defaulted_query (const char *ctlstr, con
       n_string = "[n]";
     }
 
+  /* Automatically answer the default value if the user did not want
+     prompts.  */
+  if (! caution)
+    return def_value;
+
+  /* If input isn't coming from the user directly, just say what
+     question we're asking, and then answer "yes" automatically.  This
+     way, important error messages don't get lost when talking to GDB
+     over a pipe.  */
+  if (! input_from_terminal_p ())
+    {
+      wrap_here ("");
+      vfprintf_filtered (gdb_stdout, ctlstr, args);
+
+      printf_filtered (_("(%s or %s) [answered %c; input not from terminal]\n"),
+		       y_string, n_string, def_answer);
+      gdb_flush (gdb_stdout);
+
+      return def_value;
+    }
+
   /* Automatically answer the default value if input is not from the user
      directly, or if the user did not want prompts.  */
   if (!input_from_terminal_p () || !caution)
@@ -1256,6 +1206,9 @@ defaulted_query (const char *ctlstr, con
       return deprecated_query_hook (ctlstr, args);
     }
 
+  /* Format the question outside of the loop, to avoid reusing args.  */
+  question = xstrvprintf (ctlstr, args);
+
   while (1)
     {
       wrap_here ("");		/* Flush any buffered output */
@@ -1264,7 +1217,7 @@ defaulted_query (const char *ctlstr, con
       if (annotation_level > 1)
 	printf_filtered (("\n\032\032pre-query\n"));
 
-      vfprintf_filtered (gdb_stdout, ctlstr, args);
+      fputs_filtered (question, gdb_stdout);
       printf_filtered (_("(%s or %s) "), y_string, n_string);
 
       if (annotation_level > 1)
@@ -1298,10 +1251,12 @@ defaulted_query (const char *ctlstr, con
 	  retval = !def_value;
 	  break;
 	}
-      /* Otherwise, for the default, the user may either specify
-         the required input or have it default by entering nothing.  */
-      if (answer == def_answer || answer == '\n' || 
-	  answer == '\r' || answer == EOF)
+      /* Otherwise, if a default was specified, the user may either
+         specify the required input or have it default by entering
+         nothing.  */
+      if (answer == def_answer
+	  || (defchar != '\0' &&
+	      (answer == '\n' || answer == '\r' || answer == EOF)))
 	{
 	  retval = def_value;
 	  break;
@@ -1311,6 +1266,7 @@ defaulted_query (const char *ctlstr, con
 		       y_string, n_string);
     }
 
+  xfree (question);
   if (annotation_level > 1)
     printf_filtered (("\n\032\032post-query\n"));
   return retval;
@@ -1349,6 +1305,21 @@ yquery (const char *ctlstr, ...)
   va_end (args);
 }
 
+/* Ask user a y-or-n question and return 1 iff answer is yes.
+   Takes three args which are given to printf to print the question.
+   The first, a control string, should end in "? ".
+   It should not say how to answer, because we do that.  */
+
+int
+query (const char *ctlstr, ...)
+{
+  va_list args;
+
+  va_start (args, ctlstr);
+  return defaulted_query (ctlstr, '\0', args);
+  va_end (args);
+}
+
 /* Print an error message saying that we couldn't make sense of a
    \^mumble sequence in a string or character constant.  START and END
    indicate a substring of some larger string that contains the