data_pool_* symbol visibility

[paravoid]

The new data_pool_* functions seem to be internal-only (or are at least undocumented?) but they appear on the library's exported symbols:

$ objdump -T libmaxminddb.so.0.0.7 | grep data_pool
0000000000003ce0 g    DF .text	000000000000007a  Base        data_pool_new
0000000000003e20 g    DF .text	0000000000000023  Base        data_pool_lookup
0000000000003cb0 g    DF .text	0000000000000022  Base        data_pool_destroy
0000000000003e50 g    DF .text	0000000000000054  Base        data_pool_to_list
0000000000003d60 g    DF .text	00000000000000b6  Base        data_pool_alloc

These can be hidden using gcc/ld tricks, like the visibility attribute or a version script with e.g. a MMDB_* pattern.

[paravoid]

I've tried this:

--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,7 +4,7 @@ lib_LTLIBRARIES = libmaxminddb.la
 
 libmaxminddb_la_SOURCES = maxminddb.c maxminddb-compat-util.h \
        data-pool.c data-pool.h
-libmaxminddb_la_LDFLAGS = -version-info 0:7:0
+libmaxminddb_la_LDFLAGS = -version-info 0:7:0 -export-symbols-regex '^MMDB_.*'
 include_HEADERS = $(top_srcdir)/include/maxminddb.h
 
 pkgconfig_DATA = libmaxminddb.pc

…but then apparently the data pool test fails with:

data_pool_t-data-pool-t.o: In function `test_data_pool_new':
./t/data-pool-t.c:24: undefined reference to `data_pool_new'
./t/data-pool-t.c:29: undefined reference to `data_pool_new'
./t/data-pool-t.c:34: undefined reference to `data_pool_new'
./t/data-pool-t.c:39: undefined reference to `data_pool_destroy'
[etc.]

[horgh]

Hi @paravoid. Great catch! Yeah, they are intended to be internal.

Regarding the problem with the test, we could possibly do something like this:

--- a/t/Makefile.am
+++ b/t/Makefile.am
@@ -18,6 +18,7 @@ check_PROGRAMS = \

 data_pool_t_CFLAGS = $(CFLAGS) -I$(top_srcdir)/src
 data_pool_t_LDFLAGS = $(AM_LDFLAGS) -lm
+data_pool_t_SOURCES = data-pool-t.c $(top_builddir)/src/data-pool.c

 threads_t_CFLAGS = $(CFLAGS) -pthread

[paravoid]

Thanks for the super quick response! That's a smart idea, I can confirm that the combination of the two patches above work as intended.

[horgh]

Cool, thanks for trying it!

As you did most of the work, would you want to make a PR with these changes? Otherwise I'll do so.