Feature: Macros for identifying the wide and narrow execution string literal encoding

gcc/c-family
	* c-cppbuiltin.c (c_cpp_builtins): Add predefined
	{__GNUC_EXECUTION_CHARSET_NAME} and
	_WIDE_EXECUTION_CHARSET_NAME} macros.

gcc/
	* doc/cpp.texi: Document new macros.

gcc/testsuite/
	* c-c++-common/cpp/wide-narrow-predef-macros.c: New test.

libcpp/
	* charset.c (init_iconv_desc): Initialize "to" and "from" fields.
	* directives.c (cpp_get_narrow_charset_name): New function.
	(cpp_get_wide_charset_name): Likewise.
	* include/cpplib.h (cpp_get_narrow_charset_name): Prototype.
	(cpp_get_wide_charset_name): Likewise.
	* internal.h (cset_converter): Add "to" and "from" fields.

3 files changed, 29 insertions, 0 deletions

diff --git a/gcc/c-family/c-cppbuiltin.c b/gcc/c-family/c-cppbuiltin.c
index 41914f6..7b7b07d 100644
--- a/gcc/c-family/c-cppbuiltin.c
+++ b/gcc/c-family/c-cppbuiltin.c
@@ -877,6 +877,13 @@ c_cpp_builtins (cpp_reader *pfile)
 
   define_language_independent_builtin_macros (pfile);
 
+  /* encoding definitions used by users and libraries  */
+  builtin_define_with_value ("__GNUC_EXECUTION_CHARSET_NAME",
+    cpp_get_narrow_charset_name (pfile), 1);
+  builtin_define_with_value ("__GNUC_WIDE_EXECUTION_CHARSET_NAME",
+    cpp_get_wide_charset_name (pfile), 1);
+
+
   if (c_dialect_cxx ())
   {
     int major;
diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 291e146..5dcd672 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -2451,6 +2451,15 @@ features are supported by GCC.
 @item __NO_MATH_ERRNO__
 This macro is defined if @option{-fno-math-errno} is used, or enabled
 by another option such as @option{-ffast-math} or by default.
+
+@item __GNUC_EXECUTION_CHARSET_NAME
+@itemx __GNUC_WIDE_EXECUTION_CHARSET_NAME
+These macros are defined to expand to a narrow string literal of
+the name of the narrow and wide compile-time execution character
+set used.  It directly reflects the name passed to the options
+@option{-fexec-charset} and @option{-fwide-exec-charset}, or the defaults
+documented for those options (that is, it can expand to something like
+@code{"UTF-8"}).  @xref{Invocation}.
 @end table
 
 @node System-specific Predefined Macros
diff --git a/gcc/testsuite/c-c++-common/cpp/wide-narrow-predef-macros.c b/gcc/testsuite/c-c++-common/cpp/wide-narrow-predef-macros.c
new file mode 100644
index 0000000..d5440f8a
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/wide-narrow-predef-macros.c
@@ -0,0 +1,13 @@
+/*
+   { dg-do compile }
+ */
+
+#if !defined(__GNUC_EXECUTION_CHARSET_NAME)
+#error "Required implementation macro for comple-time charset name is not present"
+#endif
+#if !defined(__GNUC_WIDE_EXECUTION_CHARSET_NAME)
+#error "Required implementation macro for wide comple-time charset name is not present"
+#endif
+
+const char narrow_name[] = __GNUC_EXECUTION_CHARSET_NAME;
+const char wide_name[] = __GNUC_WIDE_EXECUTION_CHARSET_NAME;