Disconnect -Wabi=<n> from -fabi-compat-version=<n>.

gcc/c-family/
	* c-common.h (abi_compat_version_crosses): New.
	(warn_abi_version): Declare.
	* c-common.c: Define it.
	* c-opts.c (c_common_post_options): Handle it.
	flag_abi_compat_version defaults to 8.
gcc/cp/
	* mangle.c (abi_warn_or_compat_version_crosses): New.
	Use it instead of abi_version_crosses.
	(mangle_decl): Deal with -fabi-compat-version and -Wabi separately.

From-SVN: r228017

4 files changed, 37 insertions, 10 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 5fa1a72..bccbbfa 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,11 @@
+2015-09-22  Jason Merrill  <jason@redhat.com>
+
+	* c-common.h (abi_compat_version_crosses): New.
+	(warn_abi_version): Declare.
+	* c-common.c: Define it.
+	* c-opts.c (c_common_post_options): Handle it.
+	flag_abi_compat_version defaults to 8.
+
 2015-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>
 
 	Complete the implementation of N4230, Nested namespace definition.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 4b922bf..879f4db 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -239,6 +239,9 @@ const char *constant_string_class_name;
 
 /* C++ language option variables.  */
 
+/* The reference version of the ABI for -Wabi.  */
+
+int warn_abi_version = -1;
 
 /* Nonzero means generate separate instantiation control files and
    juggle them at link time.  */
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 74d1bc1..0b4d993 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -648,14 +648,24 @@ extern const char *constant_string_class_name;
 
 /* C++ language option variables.  */
 
+/* The reference version of the ABI for -Wabi.  */
+
+extern int warn_abi_version;
 
 /* Return TRUE if one of {flag_abi_version,flag_abi_compat_version} is
-   less than N and the other is at least N, for use by -Wabi.  */
-#define abi_version_crosses(N)			\
+   less than N and the other is at least N.  */
+#define abi_compat_version_crosses(N)		\
   (abi_version_at_least(N)			\
    != (flag_abi_compat_version == 0		\
        || flag_abi_compat_version >= (N)))
 
+/* Return TRUE if one of {flag_abi_version,warn_abi_version} is
+   less than N and the other is at least N, for use by -Wabi.  */
+#define abi_version_crosses(N)			\
+  (abi_version_at_least(N)			\
+   != (warn_abi_version == 0			\
+       || warn_abi_version >= (N)))
+
 /* Nonzero means generate separate instantiation control files and
    juggle them at link time.  */
 
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index f358b62..bf2e6b0 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -397,7 +397,9 @@ c_common_handle_option (size_t scode, const char *arg, int value,
 	  warning (0, "%<-Wabi=1%> is not supported, using =2");
 	  value = 2;
 	}
-      flag_abi_compat_version = value;
+      warn_abi_version = value;
+      if (flag_abi_compat_version == -1)
+	flag_abi_compat_version = value;
       break;
 
     case OPT_fcanonical_system_headers:
@@ -870,6 +872,14 @@ c_common_post_options (const char **pfilename)
   if (flag_declone_ctor_dtor == -1)
     flag_declone_ctor_dtor = optimize_size;
 
+  if (warn_abi_version == -1)
+    {
+      if (flag_abi_compat_version != -1)
+	warn_abi_version = flag_abi_compat_version;
+      else
+	warn_abi_version = 0;
+    }
+
   if (flag_abi_compat_version == 1)
     {
       warning (0, "%<-fabi-compat-version=1%> is not supported, using =2");
@@ -877,13 +887,9 @@ c_common_post_options (const char **pfilename)
     }
   else if (flag_abi_compat_version == -1)
     {
-      /* Generate compatibility aliases for ABI v2 (3.4-4.9) by default. */
-      flag_abi_compat_version = (flag_abi_version == 0 ? 2 : 0);
-
-      /* But don't warn about backward compatibility unless explicitly
-	 requested with -Wabi=n.  */
-      if (flag_abi_version == 0)
-	warn_abi = false;
+      /* Generate compatibility aliases for ABI v8 (5.1) by default. */
+      flag_abi_compat_version
+	= (flag_abi_version == 0 ? 8 : 0);
     }
 
   /* Change flag_abi_version to be the actual current ABI level for the