Re: [PATCH] Allow embedded timestamps by C/C++ macros to be set externally

[Martin Sebor <msebor@gmail.com>]

> In the debian reproducible builds project we have considered several
> options to address this issue. We considered redefining the __DATE__ and
> __TIME__ defines by command line flags passed to gcc, but as you say,
> that triggers warnings, which could become errors when building with
> -Werror and thus may require manual intervention on many packages.

Would replacing the localtime function with one of your own
in a DSO and preloading the DSO when invoking GCC be a viable
solution? E.g., like so:

$ cat time.c && gcc -Wall -fpic -o libtime.so -shared time.c && echo 
"__DATE__ __TIME__" | LD_PRELOAD=./libtime.so gcc -E -xc -
#include <time.h>
static struct tm t;
struct tm *localtime (const time_t *timer) { return &t; }
# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "<stdin>"
"Jan  0 1900" "00:00:00"

Martin