This patch enables reproducible builds of cygwin package in conjunction
with this cygport patch:
https://sourceware.org/pipermail/cygwin-apps/2023-August/043108.html
cygwin.cygport was enhanced for the test as described in the above post.
If the same build path, SOURCE_DATE_EPOCH and toolchain are used,
rebuilds with cygport produce identical distribution tarballs. Adding
proper -fmacro-prefix-map gcc options (or remove all usages of __FILE__)
could possibly make this independent from the build path.
Note that 'u' (replace with newer objects only) flag needed to be
removed from ar commands because it is incompatible with 'D'
(deterministic archive). I don't expect any negative effect because
existing .a files are always removed before ar is run.
Not yet tested with different machines or different users accounts.
Patch would be much simpler (mkvers.sh only) if binutils would support
SOURCE_DATE_EPOCH directly.
--
Regards,
Christian
From b877330d53b95a88f1aef0fa3d14e97910d9dd2a Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.fra...@t-online.de>
Date: Tue, 5 Sep 2023 18:32:49 +0200
Subject: [PATCH] Add initial support for SOURCE_DATE_EPOCH
If specified, set version timestamp to this value.
Enable deterministic archives for ar and ranlib.
Set cygwin1.dll PE and export table header timestamps
to zero.
Signed-off-by: Christian Franke <christian.fra...@t-online.de>
---
winsup/cygwin/Makefile.am | 6 ++++++
winsup/cygwin/scripts/mkimport | 6 +++++-
winsup/cygwin/scripts/mkvers.sh | 4 ++--
winsup/cygwin/scripts/speclib | 6 +++++-
4 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/winsup/cygwin/Makefile.am b/winsup/cygwin/Makefile.am
index 9912b5399..64b252a22 100644
--- a/winsup/cygwin/Makefile.am
+++ b/winsup/cygwin/Makefile.am
@@ -572,6 +572,10 @@ toollib_DATA = \
libgmon_a_SOURCES = $(GMON_FILES)
libgmon_a_LIBADD =
+# Enable deterministic archives for reproducible builds.
+ARFLAGS = cr$${SOURCE_DATE_EPOCH:+D}
+override RANLIB := $(RANLIB)$${SOURCE_DATE_EPOCH:+ -D}
+
# cygserver library
cygserver_blddir = ${target_builddir}/winsup/cygserver
LIBSERVER = $(cygserver_blddir)/libcygserver.a
@@ -589,12 +593,14 @@ $(LDSCRIPT): $(LDSCRIPT).in
$(AM_V_GEN)$(CC) -E - -P < $^ -o $@
# cygwin dll
+# Set PE and export table header timestamps to zero for reproducible builds.
$(NEW_DLL_NAME): $(LDSCRIPT) libdll.a $(VERSION_OFILES) $(LIBSERVER)\
$(newlib_build)/libm.a $(newlib_build)/libc.a
$(AM_V_CXXLD)$(CXX) $(CXXFLAGS) \
-mno-use-libstdc-wrappers \
-Wl,--gc-sections -nostdlib -Wl,-T$(LDSCRIPT) \
-Wl,--dynamicbase -static \
+ $${SOURCE_DATE_EPOCH:+-Wl,--no-insert-timestamp} \
-Wl,--heap=0 -Wl,--out-implib,cygdll.a -shared -o $@ \
-e @DLL_ENTRY@ $(DEF_FILE) \
-Wl,-whole-archive libdll.a -Wl,-no-whole-archive \
diff --git a/winsup/cygwin/scripts/mkimport b/winsup/cygwin/scripts/mkimport
index 7684a8f0e..9517c4e9e 100755
--- a/winsup/cygwin/scripts/mkimport
+++ b/winsup/cygwin/scripts/mkimport
@@ -92,8 +92,12 @@ for my $f (keys %text) {
}
}
+# Enable deterministic archives for reproducible builds.
+my $opts = 'crs';
+$opts .= 'D' if ($ENV{'SOURCE_DATE_EPOCH'} != '');
+
unlink $libdll;
-system $ar, 'crus', $libdll, glob('*.o'), @ARGV;
+system $ar, $opts, $libdll, glob('*.o'), @ARGV;
unlink glob('*.o');
exit 1 if $?;
diff --git a/winsup/cygwin/scripts/mkvers.sh b/winsup/cygwin/scripts/mkvers.sh
index 96af936ec..38f439cd0 100755
--- a/winsup/cygwin/scripts/mkvers.sh
+++ b/winsup/cygwin/scripts/mkvers.sh
@@ -56,9 +56,9 @@ parse_preproc_flags $CC
#
-# Load the current date so we can work on individual fields
+# Load the current date (or SOURCE_DATE_EPOCH) so we can work on individual
fields
#
-set -$- $(date -u +"%m %d %Y %H:%M")
+set -$- $(date ${SOURCE_DATE_EPOCH:+-d @}${SOURCE_DATE_EPOCH} -u +"%m %d %Y
%H:%M")
m=$1 d=$2 y=$3 hhmm=$4
#
# Set date into YYYY-MM-DD HH:MM:SS format
diff --git a/winsup/cygwin/scripts/speclib b/winsup/cygwin/scripts/speclib
index e6d4d8e94..41a3a8e13 100755
--- a/winsup/cygwin/scripts/speclib
+++ b/winsup/cygwin/scripts/speclib
@@ -74,7 +74,11 @@ EOF
close $as_fd or exit 1;
system $objcopy, '-j', '.idata$7', $iname_o;
-$res = system $ar, 'crus', $lib, sort keys %extract;
+# Enable deterministic archives for reproducible builds.
+my $opts = 'crs';
+$opts .= 'D' if ($ENV{'SOURCE_DATE_EPOCH'} != '');
+
+$res = system $ar, $opts, $lib, sort keys %extract;
unlink keys %extract;
die "$0: ar creation of $lib exited with non-zero status\n" if $res;
exit 0;
--
2.39.0
