diagnostic: add permerror variants with opt

In the discussion of promoting some pedwarns to be errors by default, rather
than move them all into -fpermissive it seems to me to make sense to support
DK_PERMERROR with an option flag.  This way will also work with
-fpermissive, but users can also still use -Wno-error=narrowing to downgrade
that specific diagnostic rather than everything affected by -fpermissive.

So, for diagnostics that we want to make errors by default we can just
change the pedwarn call to permerror.

The tests check desired behavior for such a permerror in a system header
with various flags.  The patch preserves the existing permerror behavior of
ignoring -w and system headers by default, but respecting them when
downgraded to a warning by -fpermissive.

This seems similar to but a bit better than the approach of forcing
-pedantic-errors that I previously used for -Wnarrowing: specifically, in
that now -w by itself is not enough to silence the -Wnarrowing
error (integer-pack2.C).

gcc/ChangeLog:

	* doc/invoke.texi: Move -fpermissive to Warning Options.
	* diagnostic.cc (update_effective_level_from_pragmas): Remove
	redundant system header check.
	(diagnostic_report_diagnostic): Move down syshdr/-w check.
	(diagnostic_impl): Handle DK_PERMERROR with an option number.
	(permerror): Add new overloads.
	* diagnostic-core.h (permerror): Declare them.

gcc/cp/ChangeLog:

	* typeck2.cc (check_narrowing): Use permerror.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/integer-pack2.C: Add -fpermissive.
	* g++.dg/diagnostic/sys-narrow.h: New test.
	* g++.dg/diagnostic/sys-narrow1.C: New test.
	* g++.dg/diagnostic/sys-narrow1a.C: New test.
	* g++.dg/diagnostic/sys-narrow1b.C: New test.
	* g++.dg/diagnostic/sys-narrow1c.C: New test.
	* g++.dg/diagnostic/sys-narrow1d.C: New test.
	* g++.dg/diagnostic/sys-narrow1e.C: New test.
	* g++.dg/diagnostic/sys-narrow1f.C: New test.
	* g++.dg/diagnostic/sys-narrow1g.C: New test.
	* g++.dg/diagnostic/sys-narrow1h.C: New test.
	* g++.dg/diagnostic/sys-narrow1i.C: New test.

gcc/cp/typeck2.cc

@@ -1109,15 +1109,11 @@ check_narrowing (tree type, tree init, tsubst_flags_t complain,
       else if (complain & tf_error)
 	{
 	  int savederrorcount = errorcount;
-	  if (!flag_permissive)
-	    global_dc->pedantic_errors = 1;
-	  auto s = make_temp_override (global_dc->dc_warn_system_headers, true);
-	  pedwarn (loc, OPT_Wnarrowing,
-		   "narrowing conversion of %qE from %qH to %qI",
-		   init, ftype, type);
+	  permerror (loc, OPT_Wnarrowing,
+		     "narrowing conversion of %qE from %qH to %qI",
+		     init, ftype, type);
 	  if (errorcount == savederrorcount)
 	    ok = true;
-	  global_dc->pedantic_errors = flag_pedantic_errors;
 	}
     }
 

gcc/diagnostic-core.h

@@ -105,6 +105,9 @@ extern bool pedwarn (rich_location *, int, const char *, ...)
 extern bool permerror (location_t, const char *, ...) ATTRIBUTE_GCC_DIAG(2,3);
 extern bool permerror (rich_location *, const char *,
 				   ...) ATTRIBUTE_GCC_DIAG(2,3);
+extern bool permerror (location_t, int, const char *, ...) ATTRIBUTE_GCC_DIAG(3,4);
+extern bool permerror (rich_location *, int, const char *,
+		       ...) ATTRIBUTE_GCC_DIAG(3,4);
 extern void sorry (const char *, ...) ATTRIBUTE_GCC_DIAG(1,2);
 extern void sorry_at (location_t, const char *, ...) ATTRIBUTE_GCC_DIAG(2,3);
 extern void inform (location_t, const char *, ...) ATTRIBUTE_GCC_DIAG(2,3);

gcc/diagnostic.cc

@@ -1241,14 +1241,6 @@ static diagnostic_t
 update_effective_level_from_pragmas (diagnostic_context *context,
 				     diagnostic_info *diagnostic)
 {
-  if (diagnostic->m_iinfo.m_allsyslocs && !context->dc_warn_system_headers)
-    {
-      /* Ignore the diagnostic if all the inlined locations are
-	 in system headers and -Wno-system-headers is in effect.  */
-      diagnostic->kind = DK_IGNORED;
-      return DK_IGNORED;
-    }
-
   if (context->n_classification_history <= 0)
     return DK_UNSPECIFIED;
 
@@ -1489,24 +1481,16 @@ bool
 diagnostic_report_diagnostic (diagnostic_context *context,
 			      diagnostic_info *diagnostic)
 {
-  location_t location = diagnostic_location (diagnostic);
   diagnostic_t orig_diag_kind = diagnostic->kind;
 
   gcc_assert (context->m_output_format);
 
   /* Give preference to being able to inhibit warnings, before they
      get reclassified to something else.  */
-  bool report_warning_p = true;
-  if (diagnostic->kind == DK_WARNING || diagnostic->kind == DK_PEDWARN)
-    {
-      if (context->dc_inhibit_warnings)
-	return false;
-      /* Remember the result of the overall system header warning setting
-	 but proceed to also check the inlining context.  */
-      report_warning_p = diagnostic_report_warnings_p (context, location);
-      if (!report_warning_p && diagnostic->kind == DK_PEDWARN)
-	return false;
-    }
+  bool was_warning = (diagnostic->kind == DK_WARNING
+		      || diagnostic->kind == DK_PEDWARN);
+  if (was_warning && context->dc_inhibit_warnings)
+    return false;
 
   if (diagnostic->kind == DK_PEDWARN)
     {
@@ -1546,9 +1530,12 @@ diagnostic_report_diagnostic (diagnostic_context *context,
   if (!diagnostic_enabled (context, diagnostic))
     return false;
 
-  if (!report_warning_p && diagnostic->m_iinfo.m_allsyslocs)
-    /* Bail if the warning is not to be reported because all locations
-       in the inlining stack (if there is one) are in system headers.  */
+  if ((was_warning || diagnostic->kind == DK_WARNING)
+      && ((!context->dc_warn_system_headers
+	   && diagnostic->m_iinfo.m_allsyslocs)
+	  || context->dc_inhibit_warnings))
+    /* Bail if the warning is not to be reported because all locations in the
+       inlining stack (if there is one) are in system headers.  */
     return false;
 
   if (diagnostic->kind != DK_NOTE && diagnostic->kind != DK_ICE)
@@ -1738,7 +1725,8 @@ diagnostic_impl (rich_location *richloc, const diagnostic_metadata *metadata,
     {
       diagnostic_set_info (&diagnostic, gmsgid, ap, richloc,
 			   permissive_error_kind (global_dc));
-      diagnostic.option_index = permissive_error_option (global_dc);
+      diagnostic.option_index = (opt != -1 ? opt
+				 : permissive_error_option (global_dc));
     }
   else
     {
@@ -2034,6 +2022,37 @@ permerror (rich_location *richloc, const char *gmsgid, ...)
   return ret;
 }
 
+/* Similar to the above, but controlled by a flag other than -fpermissive.
+   As above, an error by default or a warning with -fpermissive, but this
+   diagnostic can also be downgraded by -Wno-error=opt.  */
+
+bool
+permerror (location_t location, int opt, const char *gmsgid, ...)
+{
+  auto_diagnostic_group d;
+  va_list ap;
+  va_start (ap, gmsgid);
+  rich_location richloc (line_table, location);
+  bool ret = diagnostic_impl (&richloc, NULL, opt, gmsgid, &ap, DK_PERMERROR);
+  va_end (ap);
+  return ret;
+}
+
+/* Same as "permerror" above, but at RICHLOC.  */
+
+bool
+permerror (rich_location *richloc, int opt, const char *gmsgid, ...)
+{
+  gcc_assert (richloc);
+
+  auto_diagnostic_group d;
+  va_list ap;
+  va_start (ap, gmsgid);
+  bool ret = diagnostic_impl (richloc, NULL, opt, gmsgid, &ap, DK_PERMERROR);
+  va_end (ap);
+  return ret;
+}
+
 /* A hard error: the code is definitely ill-formed, and an object file
    will not be produced.  */
 void

gcc/doc/invoke.texi

@@ -231,7 +231,7 @@ in the following sections.
 -fnew-inheriting-ctors
 -fnew-ttp-matching
 -fno-nonansi-builtins  -fnothrow-opt  -fno-operator-names
--fno-optional-diags  -fpermissive
+-fno-optional-diags
 -fno-pretty-templates
 -fno-rtti  -fsized-deallocation
 -ftemplate-backtrace-limit=@var{n}
@@ -323,7 +323,7 @@ Objective-C and Objective-C++ Dialects}.
 @item Warning Options
 @xref{Warning Options,,Options to Request or Suppress Warnings}.
 @gccoptlist{-fsyntax-only  -fmax-errors=@var{n}  -Wpedantic
--pedantic-errors
+-pedantic-errors -fpermissive
 -w  -Wextra  -Wall  -Wabi=@var{n}
 -Waddress  -Wno-address-of-packed-member  -Waggregate-return
 -Walloc-size-larger-than=@var{byte-size}  -Walloc-zero
@@ -3501,12 +3501,6 @@ Disable diagnostics that the standard says a compiler does not need to
 issue.  Currently, the only such diagnostic issued by G++ is the one for
 a name having multiple meanings within a class.
 
-@opindex fpermissive
-@item -fpermissive
-Downgrade some diagnostics about nonconformant code from errors to
-warnings.  Thus, using @option{-fpermissive} allows some
-nonconforming code to compile.
-
 @opindex fno-pretty-templates
 @opindex fpretty-templates
 @item -fno-pretty-templates
@@ -6167,6 +6161,18 @@ errors by @option{-pedantic-errors}.  For instance:
 -Wwrite-strings @r{(C++11 or later)}
 }
 
+@opindex fpermissive
+@item -fpermissive
+Downgrade some required diagnostics about nonconformant code from
+errors to warnings.  Thus, using @option{-fpermissive} allows some
+nonconforming code to compile.  Some C++ diagnostics are controlled
+only by this flag, but it also downgrades some diagnostics that have
+their own flag:
+
+@gccoptlist{
+-Wnarrowing @r{(C++)}
+}
+
 @opindex Wall
 @opindex Wno-all
 @item -Wall

gcc/testsuite/g++.dg/diagnostic/sys-narrow.h

@@ -0,0 +1,2 @@
+#pragma GCC system_header
+int i = { 2.4 }; // C++11 error: narrowing conversion

gcc/testsuite/g++.dg/diagnostic/sys-narrow1.C

@@ -0,0 +1,4 @@
+// { dg-do compile { target c++11 } }
+
+// { dg-error "narrowing" "" { target *-*-* } 2 }
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1a.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-w" }
+
+// { dg-error "narrowing" "" { target *-*-* } 2 }
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1b.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wno-error" }
+
+// { dg-error "narrowing" "" { target *-*-* } 2 }
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1c.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wno-error=narrowing" }
+
+// No diagnostic.
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1d.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-fpermissive" }
+
+// No diagnostic.
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1e.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-fpermissive -Wsystem-headers" }
+
+// { dg-warning "narrowing" "" { target *-*-* } 2 }
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1f.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wno-narrowing" }
+
+// No diagnostic
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1g.C

@@ -0,0 +1,5 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wno-error=narrowing -Wsystem-headers" }
+
+// { dg-warning "narrowing" "" { target *-*-* } 2 }
+#include "sys-narrow.h"

gcc/testsuite/g++.dg/diagnostic/sys-narrow1h.C

@@ -0,0 +1,6 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wno-error=narrowing -w" }
+
+// No diagnostic
+int i = { 2.4 }; // C++11 error: narrowing conversion
+

gcc/testsuite/g++.dg/diagnostic/sys-narrow1i.C

@@ -0,0 +1,6 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-fpermissive -w" }
+
+// No diagnostic
+int i = { 2.4 }; // C++11 error: narrowing conversion
+

gcc/testsuite/g++.dg/ext/integer-pack2.C

@@ -1,5 +1,5 @@
 // { dg-do compile { target { c++11 && int32 } } }
-// { dg-options -w }
+// { dg-options "-fpermissive -w" }
 
 template<typename T, T...> struct integer_sequence { };
 template<typename T, T num>