Re: [HACKERS] Custom compression methods (mac+lz4.h)

On Sat, Mar 20, 2021 at 05:37:07PM -0400, Tom Lane wrote:
> Justin Pryzby <pryzby(at)telsasoft(dot)com> writes:
> > On Fri, Mar 19, 2021 at 02:07:31PM -0400, Robert Haas wrote:
> >> On Fri, Mar 19, 2021 at 1:44 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> >>> configure: WARNING: lz4.h: accepted by the compiler, rejected by the preprocessor!
> >>> configure: WARNING: lz4.h: proceeding with the compiler's result
>
> >> No, I don't see this. I wonder whether this could possibly be an
> >> installation issue on Andrey's machine? If not, it must be
> >> version-dependent or installation-dependent in some way.
>
> > Andrey, can you check if latest HEAD (bbe0a81db) has these ./configure warnings ?
>
> FWIW, I also saw that, when building HEAD against MacPorts' version
> of liblz4 on an M1 Mac. config.log has
...
> Digging around, it looks like the "-I/opt/local/include" bit came
> from LZ4_CFLAGS, which we then stuck into CFLAGS, but it needed
> to be put in CPPFLAGS in order to make this test work.

If it's the same as the issue Andrey reported, then it causes a ./configure
WARNING, which is resolved by the ac_save hack, which I copied from ICU.

I'll shortly send a patchset including my tentative fix for that.

The configure.ac bits are also on this other thread:
https://www.postgresql.org/message-id/20210315180918.GW29463%40telsasoft.com
0005-re-add-wal_compression_method-lz4.patch

+if test "$with_lz4" = yes; then
+ ac_save_CPPFLAGS=$CPPFLAGS
+ CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+ # Verify we have LZ4's header files
+ AC_CHECK_HEADERS(lz4/lz4.h, [],
+ [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+ CPPFLAGS=$ac_save_CPPFLAGS
+fi

--
Justin