diagnostics: Add %{...%} pretty-format support for URLs and use it in -Wpsabi diagnostics

The following patch attempts to use the diagnostics URL support if available
to provide more information about the C++17 empty base and C++20
[[no_unique_address]] empty class ABI changes in -Wpsabi diagnostics.

in GCC 10.1 at the end of the diagnostics is then in some terminals
underlined with a dotted line and points to a (to be written) anchor in
gcc-10/changes.html which we need to write anyway.

2020-04-29  Jakub Jelinek  <jakub@redhat.com>

	* configure.ac (-with-changes-root-url): New configure option,
	defaulting to https://gcc.gnu.org/.
	* Makefile.in (CFLAGS-opts.o): Define CHANGES_ROOT_URL for
	opts.c.
	* pretty-print.c (get_end_url_string): New function.
	(pp_format): Handle %{ and %} for URLs.
	(pp_begin_url): Use pp_string instead of pp_printf.
	(pp_end_url): Use get_end_url_string.
	* opts.h (get_changes_url): Declare.
	* opts.c (get_changes_url): New function.
	* config/rs6000/rs6000-call.c: Include opts.h.
	(rs6000_discover_homogeneous_aggregate): Use %{in GCC 10.1%} instead
	of just in GCC 10.1 in diagnostics and add URL.
	* config/arm/arm.c (aapcs_vfp_is_call_or_return_candidate): Likewise.
	* config/aarch64/aarch64.c (aarch64_vfp_is_call_or_return_candidate):
	Likewise.
	* config/s390/s390.c (s390_function_arg_vector,
	s390_function_arg_float): Likewise.
	* configure: Regenerated.

	* c-format.c (PP_FORMAT_CHAR_TABLE): Add %{ and %}.

1 files changed, 56 insertions, 27 deletions

diff --git a/gcc/pretty-print.c b/gcc/pretty-print.c
index dde138b..d0dd9cb 100644
--- a/gcc/pretty-print.c
+++ b/gcc/pretty-print.c
@@ -1020,6 +1020,8 @@ pp_indent (pretty_printer *pp)
     pp_space (pp);
 }
 
+static const char *get_end_url_string (pretty_printer *);
+
 /* The following format specifiers are recognized as being client independent:
    %d, %i: (signed) integer in base ten.
    %u: unsigned integer in base ten.
@@ -1038,6 +1040,8 @@ pp_indent (pretty_printer *pp)
    %%: '%'.
    %<: opening quote.
    %>: closing quote.
+   %{: URL start.  Consumes a const char * argument for the URL.
+   %}: URL end.    Does not consume any arguments.
    %': apostrophe (should only be used in untranslated messages;
        translations should use appropriate punctuation directly).
    %@: diagnostic_event_id_ptr, for which event_id->known_p () must be true.
@@ -1051,7 +1055,7 @@ pp_indent (pretty_printer *pp)
    Arguments can be used sequentially, or through %N$ resp. *N$
    notation Nth argument after the format string.  If %N$ / *N$
    notation is used, it must be used for all arguments, except %m, %%,
-   %<, %> and %', which may not have a number, as they do not consume
+   %<, %>, %} and %', which may not have a number, as they do not consume
    an argument.  When %M$.*N$s is used, M must be N + 1.  (This may
    also be written %M$.*s, provided N is not otherwise used.)  The
    format string must have conversion specifiers with argument numbers
@@ -1084,7 +1088,7 @@ pp_format (pretty_printer *pp, text_info *text)
   /* Formatting phase 1: split up TEXT->format_spec into chunks in
      pp_buffer (PP)->args[].  Even-numbered chunks are to be output
      verbatim, odd-numbered chunks are format specifiers.
-     %m, %%, %<, %>, and %' are replaced with the appropriate text at
+     %m, %%, %<, %>, %} and %' are replaced with the appropriate text at
      this point.  */
 
   memset (formatters, 0, sizeof formatters);
@@ -1133,6 +1137,15 @@ pp_format (pretty_printer *pp, text_info *text)
 	  p++;
 	  continue;
 
+	case '}':
+	  {
+	    const char *endurlstr = get_end_url_string (pp);
+	    obstack_grow (&buffer->chunk_obstack, endurlstr,
+			  strlen (endurlstr));
+	  }
+	  p++;
+	  continue;
+
 	case 'R':
 	  {
 	    const char *colorstr = colorize_stop (pp_show_color (pp));
@@ -1445,6 +1458,10 @@ pp_format (pretty_printer *pp, text_info *text)
 	  }
 	  break;
 
+	case '{':
+	  pp_begin_url (pp, va_arg (*text->args_ptr, const char *));
+	  break;
+
 	default:
 	  {
 	    bool ok;
@@ -2172,18 +2189,41 @@ void
 pp_begin_url (pretty_printer *pp, const char *url)
 {
   switch (pp->url_format)
-  {
-  case URL_FORMAT_NONE:
-    break;
-  case URL_FORMAT_ST:
-    pp_printf (pp, "\33]8;;%s\33\\", url);
-    break;
-  case URL_FORMAT_BEL:
-    pp_printf (pp, "\33]8;;%s\a", url);
-    break;
-  default:
-    gcc_unreachable ();
-  }
+    {
+    case URL_FORMAT_NONE:
+      break;
+    case URL_FORMAT_ST:
+      pp_string (pp, "\33]8;;");
+      pp_string (pp, url);
+      pp_string (pp, "\33\\");
+      break;
+    case URL_FORMAT_BEL:
+      pp_string (pp, "\33]8;;");
+      pp_string (pp, url);
+      pp_string (pp, "\a");
+      break;
+    default:
+      gcc_unreachable ();
+    }
+}
+
+/* Helper function for pp_end_url and pp_format, return the "close URL" escape
+   sequence string.  */
+
+static const char *
+get_end_url_string (pretty_printer *pp)
+{
+  switch (pp->url_format)
+    {
+    case URL_FORMAT_NONE:
+      return "";
+    case URL_FORMAT_ST:
+      return "\33]8;;\33\\";
+    case URL_FORMAT_BEL:
+      return "\33]8;;\a";
+    default:
+      gcc_unreachable ();
+    }
 }
 
 /* If URL-printing is enabled, write a "close URL" escape sequence to PP.  */
@@ -2191,19 +2231,8 @@ pp_begin_url (pretty_printer *pp, const char *url)
 void
 pp_end_url (pretty_printer *pp)
 {
-  switch (pp->url_format)
-  {
-  case URL_FORMAT_NONE:
-    break;
-  case URL_FORMAT_ST:
-    pp_string (pp, "\33]8;;\33\\");
-    break;
-  case URL_FORMAT_BEL:
-    pp_string (pp, "\33]8;;\a");
-    break;
-  default:
-    gcc_unreachable ();
-  }
+  if (pp->url_format != URL_FORMAT_NONE)
+    pp_string (pp, get_end_url_string (pp));
 }
 
 #if CHECKING_P