6393b6904b
Starting with version 7, gcc automatically recognises and enforces the
environment variable SOURCE_DATE_EPOCH, and fakes __DATE__ and __TIME__
accordingly, to produce reproducible builds (at least in regards to date
and time).
However, older gcc versions do not offer this feature.
So, we use our toolchain wrapper to force-feed __DATE__ and __TIME__ as
macros, which will take precedence over those that gcc may compute
itself. We compute them according to the specs:
https://reproducible-builds.org/specs/source-date-epoch/
https://gcc.gnu.org/onlinedocs/cpp/Standard-Predefined-Macros.html
Since we define macros otherwise internal to gcc, we have to tell it not
to warn about that. The -Wno-builtin-macro-redefined flag was introduced
in gcc-4.4.0. Therefore, we make BR2_REPRODUCIBLE depend on GCC >= 4.4.
gcc-7 will ignore SOURCE_DATE_EPOCH when __DATE__ and __TIME__ are
user-defined. Anyway, this is of no consequence: whether __DATE__ and
__TIME__ or SOURCE_DATE_EPOCH takes precedence, it would yield the
exact same end result since we use the same logic to compute it. Note
that we didn't copy the code for it from gcc so using the same logic
doesn't imply that we're inheriting GPL-3.0.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jérôme Pouiller <jezz@sysmic.org>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Peter Korsgaard <peter@korsgaard.com>
[Arnout: rewrite commit message]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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| arch | ||
| board | ||
| boot | ||
| configs | ||
| docs | ||
| fs | ||
| linux | ||
| package | ||
| support | ||
| system | ||
| toolchain | ||
| utils | ||
| .defconfig | ||
| .flake8 | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .gitlab-ci.yml.in | ||
| CHANGES | ||
| Config.in | ||
| Config.in.legacy | ||
| COPYING | ||
| DEVELOPERS | ||
| Makefile | ||
| Makefile.legacy | ||
| README | ||
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on Freenode IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches