[PATCH V4] Makefile: Add build time and compiler info string

[Jessica Clarke]

On 1 Oct 2021, at 17:28, Jessica Clarke <jrtc27 at jrtc27.com> wrote:
> 
> On 1 Oct 2021, at 17:08, Bin Meng <bmeng.cn at gmail.com> wrote:
>> 
>> Hi Wei,
>> 
>> On Thu, Sep 30, 2021 at 6:12 PM <wefu at redhat.com> wrote:
>>> 
>>> From: Wei Fu <wefu at redhat.com>
>>> 
>>> When we are doing opensbi development, we want to know the build time and
>>> compiler info for debug purpose.
>>> To enable this message, please add "BUILD_INFO=y", like:
>>> 
>>> ```
>>> make BUILD_INFO=y
>>> ```
>>> 
>>> NOTE: `BUILD_INFO=y` will violate "reproducible builds".
>>> So it's ONLY for development and debug purpose, and should NOT be used
>>> in a product which follows "reproducible builds".
>>> 
>>> Signed-off-by: Wei Fu <wefu at redhat.com>
>>> ---
>>> Makefile           | 31 +++++++++++++++++++++++++++++++
>>> README.md          | 23 +++++++++++++++++++++++
>>> lib/sbi/sbi_init.c |  8 ++++++++
>>> 3 files changed, 62 insertions(+)
>>> 
>>> diff --git a/Makefile b/Makefile
>>> index 16d9dca..0158e89 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -150,6 +150,25 @@ endif
>>> # Check whether the linker supports creating PIEs
>>> OPENSBI_LD_PIE := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) $(USE_LD_FLAG) -fPIE -nostdlib -Wl,-pie -x c /dev/null -o /dev/null >/dev/null 2>&1 && echo y || echo n)
>>> 
>>> +# Build Info:
>>> +# OPENSBI_BUILD_TIME_STAMP -- the compilation time stamp
>>> +# OPENSBI_BUILD_COMPILER_VERSION -- the compiler version info
>>> +BUILD_INFO ?= n
>>> +ifeq ($(BUILD_INFO),y)
>>> +OPENSBI_BUILD_DATE_FMT = +%Y-%m-%d-%H-%M-%S %Z
>> 
>> This hour/minute/second format seems uncommon. Also for %Z it is
>> ambiguous and not better than %z, e.g.: CST could mean different time
>> zones.
> 
> -u is passed to date so it will always be UTC.

... but only for the SOURCE_DATE_EPOCH case. So yeah, %z sounds better.

Jess