[PATCH RFC] c-family: make -fno-permissive upgrade pedwarns

[Jason Merrill <jason@redhat.com>]

In the context of the recent discussion, it occurred to me that this semantic
would be useful, but currently there is no easy way to access it.  Bikeshedding
welcome; the use of this flag is a bit odd, but it has the advantage of being
accepted without error going back at least to 4.3.

-- 8< --

Currently there is no flag to use to upgrade all currently-enabled pedwarns
from warning to error.  -pedantic-errors also enables the -Wpedantic
pedwarns, while -Werror=pedantic uselessly makes only the -Wpedantic
pedwarns errors.

I suggest that since -fpermissive lowers some diagnostics from error to
warning, -fno-permissive could do the reverse.

gcc/ChangeLog:

	* doc/invoke.texi: Document -fno-permissive.

gcc/c-family/ChangeLog:

	* c.opt (fpermissive): Accept in C and ObjC as well.
	* c-opts.cc (c_common_post_options): -fno-permissive sets
	global_dc->pedantic_errors.
---
 gcc/doc/invoke.texi    | 7 +++++++
 gcc/c-family/c.opt     | 2 +-
 gcc/c-family/c-opts.cc | 4 ++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b92b8576027..6198df14382 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -3438,11 +3438,18 @@ issue.  Currently, the only such diagnostic issued by G++ is the one for
 a name having multiple meanings within a class.
 
 @opindex fpermissive
+@opindex fno-permissive
 @item -fpermissive
 Downgrade some diagnostics about nonconformant code from errors to
 warnings.  Thus, using @option{-fpermissive} allows some
 nonconforming code to compile.
 
+Conversely, @option{-fno-permissive} can be used to upgrade some
+diagnostics about nonconformant code from warnings to errors.  This
+differs from @option{-pedantic-errors} in that the latter also implies
+@option{-Wpedantic}; this option does not enable additional
+diagnostics, only upgrades the severity of those that are enabled.
+
 @opindex fno-pretty-templates
 @opindex fpretty-templates
 @item -fno-pretty-templates
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 3333cddeece..07165d2bbe8 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -2075,7 +2075,7 @@ C ObjC C++ ObjC++
 Look for and use PCH files even when preprocessing.
 
 fpermissive
-C++ ObjC++ Var(flag_permissive)
+C ObjC C++ ObjC++ Var(flag_permissive)
 Downgrade conformance errors to warnings.
 
 fplan9-extensions
diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
index c68a2a27469..1973c068d59 100644
--- a/gcc/c-family/c-opts.cc
+++ b/gcc/c-family/c-opts.cc
@@ -1021,6 +1021,10 @@ c_common_post_options (const char **pfilename)
   SET_OPTION_IF_UNSET (&global_options, &global_options_set,
 		       flag_delete_dead_exceptions, true);
 
+  if (!global_options_set.x_flag_pedantic_errors
+      && global_options_set.x_flag_permissive)
+    global_dc->pedantic_errors = !flag_permissive;
+
   if (cxx_dialect >= cxx11)
     {
       /* If we're allowing C++0x constructs, don't warn about C++98

base-commit: 62c4d34ec005e95f000ffabd34da440dc62ac346
-- 
2.31.1