Re: meson oddities

Hi,

On 2022-11-15 08:22:59 +0900, Michael Paquier wrote:
> I pass down some custom CFLAGS to the meson command as well, and these find
> their way to LDFLAGS on top of CFLAGS for the user-defined entries. I would
> not have expected that, either.

We effectively do that with autoconf as well, except that we don't mention
that in pg_config --ldflags. Our linking rules include CFLAGS, see e.g.:

%: %.o
$(CC) $(CFLAGS) $^ $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $(at)$(X)

postgres: $(OBJS)
$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LDFLAGS_EX) $(export_dynamic) $(LIBS) -o $@

ifdef PROGRAM
$(PROGRAM): $(OBJS)
$(CC) $(CFLAGS) $(OBJS) $(PG_LIBS_INTERNAL) $(LDFLAGS) $(LDFLAGS_EX) $(PG_LIBS) $(LIBS) -o $(at)$(X)
endif

# Rule for building a shared library from a single .o file
%.so: %.o
$(CC) $(CFLAGS) $< $(LDFLAGS) $(LDFLAGS_SL) -shared -o $@

Should we try that fact in pg_configin the meson build as well?

Meson automatically includes compiler flags during linking because a)
apparently many dependencies (.pc files etc) specify linker flags in CFLAGS b)
at least some kinds of LTO requires compiler flags being present during
"linking".

Greetings,

Andres Freund