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/diagnostic.h b/gcc/diagnostic.h
index 7227dae..f90d20a 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -446,6 +446,25 @@ extern void diagnostic_show_locus (diagnostic_context *,
 				   diagnostic_t diagnostic_kind);
 extern void diagnostic_show_any_path (diagnostic_context *, diagnostic_info *);
 
+/* Because we read source files a second time after the frontend did it the
+   first time, we need to know how the frontend handled things like character
+   set conversion and UTF-8 BOM stripping, in order to make everything
+   consistent.  This function needs to be called by each frontend that requires
+   non-default behavior, to inform the diagnostics infrastructure how input is
+   to be processed.  The default behavior is to do no conversion and not to
+   strip a UTF-8 BOM.
+
+   The callback should return the input charset to be used to convert the given
+   file's contents to UTF-8, or it should return NULL if no conversion is needed
+   for this file.  SHOULD_SKIP_BOM only applies in case no conversion was
+   performed, and if true, it will cause a UTF-8 BOM to be skipped at the
+   beginning of the file.  (In case a conversion was performed, the BOM is
+   rather skipped as part of the conversion process.)  */
+
+void diagnostic_initialize_input_context (diagnostic_context *context,
+					  diagnostic_input_charset_callback ccb,
+					  bool should_skip_bom);
+
 /* Force diagnostics controlled by OPTIDX to be kind KIND.  */
 extern diagnostic_t diagnostic_classify_diagnostic (diagnostic_context *,
 						    int /* optidx */,