This brings the behaviour in line with the __DATE__ and __TIME__ macros. Note
though the minor difference: __TIMESTAMP__ is defined as the file-modification
date and not the "current" date or time like the other two macros. Therefore,
we do a clamping behaviour (similar to tar --clamp-mtime).
Acknowledgements
----------------
Reiner Herrmann suggested the clamping behaviour.
ChangeLogs
----------
libcpp/ChangeLog:
2016-11-01 Ximin Luo <infini...@pwned.gg>
* macro.c (_cpp_builtin_macro_text): Use SOURCE_DATE_EPOCH in place of
__TIMESTAMP__ if the latter is newer than the former.
gcc/ChangeLog:
2016-11-01 Ximin Luo <infini...@pwned.gg>
* doc/cppenv.texi (Environment Variables): Update SOURCE_DATE_EPOCH to
describe the new effect on __TIMESTAMP__.
gcc/testsuite/ChangeLog:
2016-11-01 Ximin Luo <infini...@pwned.gg>
* gcc.dg/cpp/source_date_epoch-4.c: New test.
* gcc.dg/cpp/source_date_epoch-5.c: New test.
Index: gcc-7-20161030/libcpp/macro.c
===================================================================
--- gcc-7-20161030.orig/libcpp/macro.c
+++ gcc-7-20161030/libcpp/macro.c
@@ -264,7 +264,30 @@ _cpp_builtin_macro_text (cpp_reader *pfi
struct tm *tb = NULL;
struct stat *st = _cpp_get_file_stat (file);
if (st)
- tb = localtime (&st->st_mtime);
+ {
+ /* Set a reproducible timestamp for __DATE__ and __TIME__
macro
+ if SOURCE_DATE_EPOCH is defined. */
+ if (pfile->source_date_epoch == (time_t) -2
+ && pfile->cb.get_source_date_epoch != NULL)
+ pfile->source_date_epoch =
pfile->cb.get_source_date_epoch (pfile);
+
+ if (pfile->source_date_epoch >= (time_t) 0)
+ {
+ /* If SOURCE_DATE_EPOCH is set, we want reproducible
+ timestamps so use gmtime not localtime. */
+ if (st->st_mtime >= pfile->source_date_epoch)
+ tb = gmtime (&pfile->source_date_epoch);
+ else
+ /* Don't use SOURCE_DATE_EPOCH if the timestamp is
+ older, since that means it was probably already
+ set in a reproducible way (e.g. via source tarball
+ extraction or some other method). */
+ tb = gmtime (&st->st_mtime);
+ }
+ else
+ tb = localtime (&st->st_mtime);
+ }
+
if (tb)
{
char *str = asctime (tb);
Index: gcc-7-20161030/gcc/doc/cppenv.texi
===================================================================
--- gcc-7-20161030.orig/gcc/doc/cppenv.texi
+++ gcc-7-20161030/gcc/doc/cppenv.texi
@@ -83,8 +83,9 @@ main input file is omitted.
@item SOURCE_DATE_EPOCH
If this variable is set, its value specifies a UNIX timestamp to be
used in replacement of the current date and time in the @code{__DATE__}
-and @code{__TIME__} macros, so that the embedded timestamps become
-reproducible.
+and @code{__TIME__} macros, and in replacement of the file modification
+date in the @code{__TIMESTAMP__} macro if the latter is newer than the
+former, so that the embedded timestamps become reproducible.
The value of @env{SOURCE_DATE_EPOCH} must be a UNIX timestamp,
defined as the number of seconds (excluding leap seconds) since
Index: gcc-7-20161030/gcc/testsuite/gcc.dg/cpp/source_date_epoch-4.c
===================================================================
--- /dev/null
+++ gcc-7-20161030/gcc/testsuite/gcc.dg/cpp/source_date_epoch-4.c
@@ -0,0 +1,13 @@
+/* __TIMESTAMP__ should use SOURCE_DATE_EPOCH if the latter is older. */
+/* { dg-do run } */
+/* { dg-set-compiler-env-var TZ "UTC" } */
+/* { dg-set-compiler-env-var LC_ALL "C" } */
+/* { dg-set-compiler-env-var SOURCE_DATE_EPOCH "0" } */
+
+int
+main ()
+{
+ if (__builtin_strcmp (__TIMESTAMP__, "Thu Jan 1 00:00:00 1970") != 0)
+ __builtin_abort ();
+ return 0;
+}
Index: gcc-7-20161030/gcc/testsuite/gcc.dg/cpp/source_date_epoch-5.c
===================================================================
--- /dev/null
+++ gcc-7-20161030/gcc/testsuite/gcc.dg/cpp/source_date_epoch-5.c
@@ -0,0 +1,13 @@
+/* __TIMESTAMP__ should not use SOURCE_DATE_EPOCH if the latter is newer. */
+/* { dg-do run } */
+/* { dg-set-compiler-env-var TZ "UTC" } */
+/* { dg-set-compiler-env-var LC_ALL "C" } */
+/* { dg-set-compiler-env-var SOURCE_DATE_EPOCH "253402300799" } */
+
+int
+main ()
+{
+ if (__builtin_strcmp (__TIMESTAMP__, "Fri Dec 31 23:59:59 UTC 9999") == 0)
+ __builtin_abort ();
+ return 0;
+}
