Each dlopen_*() wrapper kept its dl handle as a file-scope
'static void *xxx_dl = NULL;' even though only the wrapper itself
ever referenced it. Move each one inside the corresponding function
so its scope matches its actual use, leaving the rest of each
translation unit free of the unused file-scope name.
In pcre2-util.c the assert(pcre2_dl) in pattern_matches_and_log()
becomes assert(sym_pcre2_match), which carries the same invariant
(pattern_compile_and_log() ran dlopen_pcre2()).
Convert the GnuTLS and libmicrohttpd usage in journal-remote to the
dlopen pattern used by other optional shared libraries. A new
src/shared/gnutls-util.{h,c} declares the GnuTLS entry points via
DLSYM_PROTOTYPE and resolves them in dlopen_gnutls(); microhttpd-util
is moved from src/journal-remote to src/shared and gains analogous
DLSYM_PROTOTYPEs plus dlopen_microhttpd(). Callers in journal-gatewayd,
journal-remote-main and microhttpd-util itself call the sym_* wrappers
and invoke dlopen_gnutls()/dlopen_microhttpd() at their entry points.
setup_gnutls_logger() no longer fails when libgnutls is missing at
runtime; it logs a notice and returns 0 so journal-gatewayd starts up
without TLS dependencies installed.
The meson files gain libgnutls_cflags and libmicrohttpd_cflags partial
dependencies that expose include paths and compile flags only. Every
systemd-journal-{gatewayd,remote,upload} target switches to the cflags
variant, dropping the direct libgnutls/libmicrohttpd link. The
gatewayd->remote object-sharing dance for microhttpd-util.o goes away
since the code now lives in libshared.
test-dlopen-so gains assertions for dlopen_gnutls and dlopen_microhttpd.
Daan De Meyer