libcpp: Provide date routine

Joseph pointed me at cb_get_source_date_epoch, which allows repeatable
builds and solves a FIXME I had on the modules branch.  Unfortunately
it's used exclusively to generate __DATE__ and __TIME__ values, which
fallback to using a time(2) call.  It'd be nicer if the preprocessor
made whatever time value it determined available to the rest of the
compiler.  So this patch adds a new cpp_get_date function, which
abstracts the call to the get_source_date_epoch hook, or uses time
directly.  The value is cached.  Thus the timestamp I end up putting
on CMI files matches __DATE__ and __TIME__ expansions.  That seems
worthwhile.

	libcpp/
	* include/cpplib.h (enum class CPP_time_kind): New.
	(cpp_get_date): Declare.
	* internal.h (struct cpp_reader): Replace source_date_epoch with
	time_stamp and time_stamp_kind.
	* init.c (cpp_create_reader): Initialize them.
	* macro.c (_cpp_builtin_macro_text): Use cpp_get_date.
	(cpp_get_date): Broken out from _cpp_builtin_macro_text and
	genericized.

1 files changed, 9 insertions, 0 deletions

diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 8e39886..c4d7cc5 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -1040,6 +1040,15 @@ inline location_t cpp_macro_definition_location (cpp_hashnode *node)
 {
   return node->value.macro->line;
 }
+/* Return an idempotent time stamp (possibly from SOURCE_DATE_EPOCH).  */
+enum class CPP_time_kind 
+{
+  FIXED = -1,	/* Fixed time via source epoch.  */
+  DYNAMIC = -2,	/* Dynamic via time(2).  */
+  UNKNOWN = -3	/* Wibbly wobbly, timey wimey.  */
+};
+extern CPP_time_kind cpp_get_date (cpp_reader *, time_t *);
+
 extern void _cpp_backup_tokens (cpp_reader *, unsigned int);
 extern const cpp_token *cpp_peek_token (cpp_reader *, int);