This should be safer for casting and more compatible with existing code bases that wrongly assume it must be defined as a pointer.
a _REDIR_TIME64 macro is introduced, which the arch's alltypes.h is expected to define, to control redirection of symbol names for interfaces that involve time_t and derived types. this ensures that object files will only be linked to libc interfaces matching the ABI whose headers they were compiled against. along with time32 compat shims, which will be introduced separately, the redirection also makes it possible for a single libc (static or shared) to be used with object files produced with either the old (32-bit time_t) headers or the new ones after 64-bit time_t switchover takes place. mixing of such object files (or shared libraries) in the same program will also be possible, but must be done with care; ABI between libc and a consumer of the libc interfaces is guaranteed to match by the the symbol name redirection, but pairwise ABI between consumers of libc that define interfaces between each other in terms of time_t is not guaranteed to match. this change adds a dependency on an additional "GNU C" feature to the public headers for existing 32-bit archs, which is generally undesirable; however, the feature is one which glibc has depended on for a long time, and thus which any viable alternative compiler is going to need to provide. 64-bit archs are not affected, nor will future 32-bit archs be, regardless of whether they are "new" on the kernel side (e.g. riscv32) or just newly-added (e.g. a new sparc or xtensa port). the same applies to newly-added ABIs for existing machine-level archs.
reported and changes suggested by Daniel Sabogal.
placing the opening brace on the same line as the struct keyword/tag
is the style I prefer and seems to be the prevailing practice in more
recent additions.
these changes were generated by the command:
find include/ arch/*/bits -name '*.h' \
-exec sed -i '/^struct [^;{]*$/{N;s/\n/ /;}' {} +
and subsequently checked by hand to ensure that the regex did not pick
up any false positives.
the vast majority of these failures seem to have been oversights at the time _BSD_SOURCE was added, or perhaps shortly afterward. the one which may have had some reason behind it is omission of setpgrp from the _BSD_SOURCE feature profile, since the standard setpgrp interface conflicts with a legacy (pre-POSIX) BSD interface by the same name. however, such omission is not aligned with our general policy in this area (for example, handling of similar _GNU_SOURCE cases) and should not be preserved.
based on patch by Jens Gustedt for inclusion with C11 threads implementation, but committed separately since it's independent of threads.
it's unclear what the historical signature for this function was, but semantically, the argument should be a pointer to const, and this is what glibc uses. correct programs should not be using this function anyway, so it's unlikely to matter.
unfortunately this eliminates the ability of the compiler to diagnose some dangerous/incorrect usage, but POSIX requires (as an extension to the C language, i.e. CX shaded) that NULL have type void *. plain C allows it to be defined as any null pointer constant. the definition 0L is preserved for C++ rather than reverting to plain 0 to avoid dangerous behavior in non-conforming programs which use NULL as a variadic sentinel. (it's impossible to use (void *)0 for C++ since C++ lacks the proper implicit pointer conversions, and other popular alternatives like the GCC __null extension seem non-conforming to the standard's requirements.)
added in linux-v3.10 commit 1ff3c9677bff7e468e0c487d0ffefe4e901d33f4