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, 3 insertions, 2 deletions

diff --git a/libcpp/init.c b/libcpp/init.c
index 6c52f50..dcf1d4b 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -273,8 +273,9 @@ cpp_create_reader (enum c_lang lang, cpp_hash_table *table,
   /* Do not force token locations by default.  */
   pfile->forced_token_location = 0;
 
-  /* Initialize source_date_epoch to -2 (not yet set).  */
-  pfile->source_date_epoch = (time_t) -2;
+  /* Note the timestamp is unset.  */
+  pfile->time_stamp = time_t (-1);
+  pfile->time_stamp_kind = 0;
 
   /* The expression parser stack.  */
   _cpp_expand_op_stack (pfile);