In some unusual, timing-dependent cases on some platforms, 'make -p' can
generate output that incorrectly makes it look like the system clock ran
backwards, when it didn't.
Also, there's a torture-test case (system clock in the far past or
future) where 'make -p' can dump core.
Proposed patch attached.
From 2e6355c4f3813c346ded2a90997a4308114d2893 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Sun, 19 Mar 2023 14:40:39 -0700
Subject: [PATCH] Fix clock skew / crash issue with 'make -p'
* NEWS: Mention this.
* src/main.c (print_data_base): Use file_timestamp_sprintf
instead of time+ctime, to avoid inconsistent clocks. See:
https://www.gnu.org/software/gnulib/manual/html_node/time.html
https://sourceware.org/bugzilla/show_bug.cgi?id=30200
This avoids output that incorrectly implies that the clock ran backwards.
Avoiding ctime also means 'make' won't have undefined behavior
if ctime crashes or returns a null pointer, which can happen if
the system clock is set far in the past or future.
---
NEWS | 5 +++++
src/main.c | 10 ++++++----
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/NEWS b/NEWS
index 4ab15136..dcce8d93 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,11 @@ which is contained in this distribution as the file doc/make.texi.
See the README file and the GNU Make manual for instructions for
reporting bugs.
+* 'make --print-data-base' (or 'make -p') now outputs more-consistent
+ timestamps, e.g., "2023-03-19 14:23:42.570558743". Previously it
+ sometimes also used the form "Sun Mar 19 14:23:42 2023", and
+ sometimes used a clock that ticked slightly inconsistently.
+
Version 4.4.1 (26 Feb 2023)
diff --git a/src/main.c b/src/main.c
index a9d3a644..2a02e399 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3744,11 +3744,13 @@ print_version (void)
static void
print_data_base (void)
{
- time_t when = time ((time_t *) 0);
+ int resolution;
+ char buf[FILE_TIMESTAMP_PRINT_LEN_BOUND + 1];
+ file_timestamp_sprintf (buf, file_timestamp_now (&resolution));
print_version ();
- printf (_("\n# Make data base, printed on %s"), ctime (&when));
+ printf (_("\n# Make data base, printed on %s"), buf);
print_variable_data_base ();
print_dir_data_base ();
@@ -3757,8 +3759,8 @@ print_data_base (void)
print_vpath_data_base ();
strcache_print_stats ("#");
- when = time ((time_t *) 0);
- printf (_("\n# Finished Make data base on %s\n"), ctime (&when));
+ file_timestamp_sprintf (buf, file_timestamp_now (&resolution));
+ printf (_("\n# Finished Make data base on %s\n"), buf);
}
static void
--
2.37.2
