Fix warning URLs for Fortran and analyzer [PR 92830]

PR 92830 reports that we always use "gcc/Warning-Options.html" when we
emit escaped documentation URLs when printing "[-Wname-of-option]" for
a warning.

This page is wrong for most Fortran warnings, and for analyzer warnings.

I considered various schemes involving adding extra tags to the .opt
format to capture where options are documented, but for now this patch
fixes the issue by introducing some special-casing logic.
It only fixes the URLs for warning options, not for other command-line
options, but those are the only options for which get_option_url is
currently called.

gcc/ChangeLog:
	PR 92830
	* configure.ac (DOCUMENTATION_ROOT_URL): Drop trailing "gcc/" from
	default value, so that it can by supplied by get_option_html_page.
	* configure: Regenerate.
	* opts.c: Include "selftest.h".
	(get_option_html_page): New function.
	(get_option_url): Use it.  Reformat to place comments next to the
	expressions they refer to.
	(selftest::test_get_option_html_page): New.
	(selftest::opts_c_tests): New.
	* selftest-run-tests.c (selftest::run_tests): Call
	selftest::opts_c_tests.
	* selftest.h (selftest::opts_c_tests): New decl.

gcc/configure

@@ -7851,7 +7851,7 @@ if test "${with_documentation_root_url+set}" = set; then :
 	   ;;
      esac
 else
-  DOCUMENTATION_ROOT_URL="https://gcc.gnu.org/onlinedocs/gcc/"
+  DOCUMENTATION_ROOT_URL="https://gcc.gnu.org/onlinedocs/"
 
 fi
 

gcc/configure.ac

@@ -982,7 +982,7 @@ AC_ARG_WITH(documentation-root-url,
       *)   DOCUMENTATION_ROOT_URL="$withval"
 	   ;;
      esac],
-     DOCUMENTATION_ROOT_URL="https://gcc.gnu.org/onlinedocs/gcc/"
+     DOCUMENTATION_ROOT_URL="https://gcc.gnu.org/onlinedocs/"
 )
 AC_SUBST(DOCUMENTATION_ROOT_URL)
 

gcc/opts.c

@@ -32,6 +32,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "spellcheck.h"
 #include "opt-suggestions.h"
 #include "diagnostic-color.h"
+#include "selftest.h"
 
 static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
 
@@ -3128,6 +3129,42 @@ option_name (diagnostic_context *context, int option_index,
     return NULL;
 }
 
+/* Get the page within the documentation for this option.  */
+
+static const char *
+get_option_html_page (int option_index)
+{
+  const cl_option *cl_opt = &cl_options[option_index];
+
+  /* Analyzer options are on their own page.  */
+  if (strstr(cl_opt->opt_text, "analyzer-"))
+    return "gcc/Static-Analyzer-Options.html";
+
+#ifdef CL_Fortran
+  if (cl_opt->flags & CL_Fortran)
+    {
+      switch (option_index)
+	{
+	default:
+	  /* Most Fortran warnings are documented on this page.  */
+	  return "gfortran/Error-and-Warning-Options.html";
+
+	case OPT_Wdate_time:
+	case OPT_Wconversion:
+	case OPT_Wconversion_extra:
+	case OPT_Wmissing_include_dirs:
+	case OPT_Wopenmp_simd:
+	  /* These warnings are marked in fortran/lang.opt as
+	     "Documented in C" and thus use the common
+	     Warning-Options page below.  */
+	  break;
+	}
+    }
+#endif
+
+  return "gcc/Warning-Options.html";
+}
+
 /* Return malloced memory for a URL describing the option OPTION_INDEX
    which enabled a diagnostic (context CONTEXT).  */
 
@@ -3135,16 +3172,50 @@ char *
 get_option_url (diagnostic_context *, int option_index)
 {
   if (option_index)
-    /* DOCUMENTATION_ROOT_URL should be supplied via -D by the Makefile
-       (see --with-documentation-root-url).
+    return concat (/* DOCUMENTATION_ROOT_URL should be supplied via -D by
+		      the Makefile (see --with-documentation-root-url), and
+		      should have a trailing slash.  */
+		   DOCUMENTATION_ROOT_URL,
 
-       Expect an anchor of the form "index-Wfoo" e.g.
-       <a name="index-Wformat"></a>, and thus an id within
-       the URL of "#index-Wformat".  */
-    return concat (DOCUMENTATION_ROOT_URL,
-		   "Warning-Options.html",
+		   /* get_option_html_page will return something like
+		      "gcc/Warning-Options.html".  */
+		   get_option_html_page (option_index),
+
+		   /* Expect an anchor of the form "index-Wfoo" e.g.
+		      <a name="index-Wformat"></a>, and thus an id within
+		      the URL of "#index-Wformat".  */
 		   "#index", cl_options[option_index].opt_text,
 		   NULL);
   else
     return NULL;
 }
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* Verify that get_option_html_page works as expected.  */
+
+static void
+test_get_option_html_page ()
+{
+  ASSERT_STREQ (get_option_html_page (OPT_Wcpp), "gcc/Warning-Options.html");
+  ASSERT_STREQ (get_option_html_page (OPT_Wanalyzer_double_free),
+	     "gcc/Static-Analyzer-Options.html");
+#ifdef CL_Fortran
+  ASSERT_STREQ (get_option_html_page (OPT_Wline_truncation),
+		"gfortran/Error-and-Warning-Options.html");
+#endif
+}
+
+/* Run all of the selftests within this file.  */
+
+void
+opts_c_tests ()
+{
+  test_get_option_html_page ();
+}
+
+} // namespace selftest
+
+#endif /* #if CHECKING_P */

gcc/selftest-run-tests.c

@@ -73,6 +73,7 @@ selftest::run_tests ()
   typed_splay_tree_c_tests ();
   unique_ptr_tests_cc_tests ();
   opt_proposer_c_tests ();
+  opts_c_tests ();
   json_cc_tests ();
   cgraph_c_tests ();
   optinfo_emit_json_cc_tests ();

gcc/selftest.h

@@ -243,6 +243,7 @@ extern void input_c_tests ();
 extern void json_cc_tests ();
 extern void opt_problem_cc_tests ();
 extern void optinfo_emit_json_cc_tests ();
+extern void opts_c_tests ();
 extern void ordered_hash_map_tests_cc_tests ();
 extern void predict_c_tests ();
 extern void pretty_print_c_tests ();