diagnostics: Support for -finput-charset [PR93067]

Adds the logic to handle -finput-charset in layout_get_source_line(), so that
source lines are converted from their input encodings prior to being output by
diagnostics machinery. Also adds the ability to strip a UTF-8 BOM similarly.

gcc/c-family/ChangeLog:

	PR other/93067
	* c-opts.c (c_common_input_charset_cb): New function.
	(c_common_post_options): Call new function
	diagnostic_initialize_input_context().

gcc/d/ChangeLog:

	PR other/93067
	* d-lang.cc (d_input_charset_callback): New function.
	(d_init): Call new function
	diagnostic_initialize_input_context().

gcc/fortran/ChangeLog:

	PR other/93067
	* cpp.c (gfc_cpp_post_options): Call new function
	diagnostic_initialize_input_context().

gcc/ChangeLog:

	PR other/93067
	* coretypes.h (typedef diagnostic_input_charset_callback): Declare.
	* diagnostic.c (diagnostic_initialize_input_context): New function.
	* diagnostic.h (diagnostic_initialize_input_context): Declare.
	* input.c (default_charset_callback): New function.
	(file_cache::initialize_input_context): New function.
	(file_cache_slot::create): Added ability to convert the input
	according to the input context.
	(file_cache::file_cache): Initialize the new input context.
	(class file_cache_slot): Added new m_alloc_offset member.
	(file_cache_slot::file_cache_slot): Initialize the new member.
	(file_cache_slot::~file_cache_slot): Handle potentially offset buffer.
	(file_cache_slot::maybe_grow): Likewise.
	(file_cache_slot::needs_read_p): Handle NULL fp, which is now possible.
	(file_cache_slot::get_next_line): Likewise.
	* input.h (class file_cache): Added input context member.

libcpp/ChangeLog:

	PR other/93067
	* charset.c (init_iconv_desc): Adapt to permit PFILE argument to
	be NULL.
	(_cpp_convert_input): Likewise. Also move UTF-8 BOM logic to...
	(cpp_check_utf8_bom): ...here.  New function.
	(cpp_input_conversion_is_trivial): New function.
	* files.c (read_file_guts): Allow PFILE argument to be NULL.  Add
	INPUT_CHARSET argument as an alternate source of this information.
	(read_file): Pass the new argument to read_file_guts.
	(cpp_get_converted_source): New function.
	* include/cpplib.h (struct cpp_converted_source): Declare.
	(cpp_get_converted_source): Declare.
	(cpp_input_conversion_is_trivial): Declare.
	(cpp_check_utf8_bom): Declare.

gcc/testsuite/ChangeLog:

	PR other/93067
	* gcc.dg/diagnostic-input-charset-1.c: New test.
	* gcc.dg/diagnostic-input-utf8-bom.c: New test.

1 files changed, 19 insertions, 0 deletions

diff --git a/gcc/d/d-lang.cc b/gcc/d/d-lang.cc
index 4386a48..fa29a46a 100644
--- a/gcc/d/d-lang.cc
+++ b/gcc/d/d-lang.cc
@@ -50,6 +50,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "output.h"
 #include "print-tree.h"
 #include "debug.h"
+#include "input.h"
 
 #include "d-tree.h"
 #include "id.h"
@@ -362,6 +363,19 @@ d_option_lang_mask (void)
   return CL_D;
 }
 
+/* Implements input charset and BOM skipping configuration for
+   diagnostics.  */
+static const char *d_input_charset_callback (const char * /*filename*/)
+{
+  /* TODO: The input charset is automatically determined by code in
+     dmd/dmodule.c based on the contents of the file.  If this detection
+     logic were factored out and could be reused here, then we would be able
+     to return UTF-16 or UTF-32 as needed here.  For now, we return always
+     NULL, which means no conversion is necessary, i.e. the input is assumed
+     to be UTF-8 when diagnostics read this file.  */
+  return nullptr;
+}
+
 /* Implements the lang_hooks.init routine for language D.  */
 
 static bool
@@ -373,6 +387,11 @@ d_init (void)
   Expression::_init ();
   Objc::_init ();
 
+  /* Diagnostics input init, to enable BOM skipping and
+     input charset conversion.  */
+  diagnostic_initialize_input_context (global_dc,
+				       d_input_charset_callback, true);
+
   /* Back-end init.  */
   global_binding_level = ggc_cleared_alloc <binding_level> ();
   current_binding_level = global_binding_level;