tree-wide: make new/new0/malloc_multiply/reallocarray safe for size 0
All underlying glibc calls are free to return NULL if the size argument
is 0. We most often call those functions with a fixed argument, or at least
something which obviously cannot be zero, but it's too easy to forget.
E.g. coverity complains about "rows = new0(JsonVariant*, n_rows-1);" in
format-table.c There is an assert that n_rows > 0, so we could hit this
corner case here. Let's simplify callers and make those functions "safe".
CID #
1397035.
The compiler is mostly able to optimize this away:
$ size build{,-opt}/src/shared/libsystemd-shared-239.so
(before)
text data bss dec hex filename
2643329 580940 3112
3227381 313ef5 build/src/shared/libsystemd-shared-239.so (-O0 -g)
2170013 578588 3089
2751690 29fcca build-opt/src/shared/libsystemd-shared-239.so (-03 -flto -g)
(after)
text data bss dec hex filename
2644017 580940 3112
3228069 3141a5 build/src/shared/libsystemd-shared-239.so
2170765 578588 3057
2752410 29ff9a build-opt/src/shared/libsystemd-shared-239.so