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openwrt/include/depends.mk
Christian Marangi 53a08e3743
build: make find_md5 reproducible with AUTOREMOVE
While experimenting with the AUTOREMOVE option in search of a way to use
prebuilt host tools in different buildroot, it was discovered that the
md5 generated by find_md5 in depends.mk is not reproducible.

Currently the hash is generated by the path of the file in addition to
the file mod time. Out of confusion, probably, there was an idea that
such command was used on the package build_dir. Reality is that this
command is run on the package files. (Makefile, patches, src)

This is problematic because the package Makefile (for example) change at
each git clone and base the hash on the Makefile mtime doesn't really
reflect if the Makefile actually changes across a buildroot or not.

A better approach is to generate an hash of each file and then generate
an hash on the sort hash list. This way we remove the problem of git
clone setting a wrong mtime while keeping the integrity of checking if a
file changed for the package as any change will result in a different
hash.

Introduce a new kind of find_md5 function, find_md5_reproducible that
apply this new logic and limit it only with AUTOREMOVE option set to
prevent any kind of slowdown due to additional hash generation.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
2022-09-30 22:26:51 +02:00

54 lines
1.5 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0-only
#
# Copyright (C) 2007-2020 OpenWrt.org
# define a dependency on a subtree
# parameters:
# 1: directories/files
# 2: directory dependency
# 3: tempfile for file listings
# 4: find options
DEP_FINDPARAMS := -x "*/.svn*" -x ".*" -x "*:*" -x "*\!*" -x "* *" -x "*\\\#*" -x "*/.*_check" -x "*/.*.swp" -x "*/.pkgdir*"
find_md5=find $(wildcard $(1)) -type f $(patsubst -x,-and -not -path,$(DEP_FINDPARAMS) $(2)) -printf "%p%T@\n" | sort | $(MKHASH) md5
find_md5_reproducible=find $(wildcard $(1)) -type f $(patsubst -x,-and -not -path,$(DEP_FINDPARAMS) $(2)) -print0 | xargs -0 $(MKHASH) md5 | sort | $(MKHASH) md5
define rdep
.PRECIOUS: $(2)
.SILENT: $(2)_check
$(2): $(2)_check
check-depends: $(2)_check
ifneq ($(wildcard $(2)),)
$(2)_check::
$(if $(3), \
$(call find_md5,$(1),$(4)) > $(3).1; \
{ [ \! -f "$(3)" ] || diff $(3) $(3).1 >/dev/null; } && \
) \
{ \
[ -f "$(2)_check.1" ] && mv "$(2)_check.1" "$(2)_check"; \
$(TOPDIR)/scripts/timestamp.pl $(DEP_FINDPARAMS) $(4) -n $(2) $(1) && { \
$(call debug_eval,$(SUBDIR),r,echo "No need to rebuild $(2)";) \
touch -r "$(2)" "$(2)_check"; \
} \
} || { \
$(call debug_eval,$(SUBDIR),r,echo "Need to rebuild $(2)";) \
touch "$(2)_check"; \
}
$(if $(3), mv $(3).1 $(3))
else
$(2)_check::
$(if $(3), rm -f $(3) $(3).1)
$(call debug_eval,$(SUBDIR),r,echo "Target $(2) not built")
endif
endef
ifeq ($(filter .%,$(MAKECMDGOALS)),$(if $(MAKECMDGOALS),$(MAKECMDGOALS),x))
define rdep
$(2): $(2)_check
endef
endif