urbit/nix/nixcrpkgs/mingw-w64/gcc/use-source-date-epoch.patch

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https://gcc.gnu.org/ml/gcc-patches/2015-06/msg02210.html
diff --git a/libcpp/macro.c b/libcpp/macro.c
index 1e0a0b5..a52e3cb 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -349,14 +349,38 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode *node)
slow on some systems. */
time_t tt;
struct tm *tb = NULL;
+ char *source_date_epoch;
- /* (time_t) -1 is a legitimate value for "number of seconds
- since the Epoch", so we have to do a little dance to
- distinguish that from a genuine error. */
- errno = 0;
- tt = time(NULL);
- if (tt != (time_t)-1 || errno == 0)
- tb = localtime (&tt);
+ /* Allow the date and time to be set externally by an exported
+ environment variable to enable reproducible builds. */
+ source_date_epoch = getenv ("SOURCE_DATE_EPOCH");
+ if (source_date_epoch)
+ {
+ errno = 0;
+ tt = (time_t) strtol (source_date_epoch, NULL, 10);
+ if (errno == 0)
+ {
+ tb = gmtime (&tt);
+ if (tb == NULL)
+ cpp_error (pfile, CPP_DL_ERROR,
+ "SOURCE_DATE_EPOCH=\"%s\" is not a valid date",
+ source_date_epoch);
+ }
+ else
+ cpp_error (pfile, CPP_DL_ERROR,
+ "SOURCE_DATE_EPOCH=\"%s\" is not a valid number",
+ source_date_epoch);
+ }
+ else
+ {
+ /* (time_t) -1 is a legitimate value for "number of seconds
+ since the Epoch", so we have to do a little dance to
+ distinguish that from a genuine error. */
+ errno = 0;
+ tt = time(NULL);
+ if (tt != (time_t)-1 || errno == 0)
+ tb = localtime (&tt);
+ }
if (tb)
{