Exported symbols aren't consistent

[Zer0-One]

jansson_withoutpatch.txt
jansson_withpatch.txt

Here are the symbol tables without the patch from #704 and with the patch. Something confusing is that this symbol version script appears to be configured only to be applied if the linker doesn't support --default-symver, and I'm using the GNU linker, which does support that flag, afaik.

The autotools build produces a clean symbol table because of the "inline version script" in src/Makefile.am .

On Windows platforms, the jansson.def file handles symbol exports in DLLs and (afaik) is ignored on unix, so for unix platforms, why are we not just using a version script everywhere and ignoring --default-symver altogether?

In any case, the symbols exported on a default cmake build on GCC currently include symbols which should be local only. The hack fix is to merge #704 , and the proper fix would be to just default to including a version script.

[parona-source]

--default-symver also introduces issues if you use non BFD linkers on Glibc with autotools.

There is an older PR that wanted to use version scripts if --default-symver wasn’t accepted by the linker to copy the approach from cmake.
#666

An explicit version script for both build systems would simplify this while fixing the build for linkers that dont support --default-symver.

[claudiushaag]

I ran into this problem on the conda-forge feedstock, where we tried to migrate to the cmake build. There, the symver did also not work.

I tried to patch things up, and from what I saw, there was a bug in the CMakeLists.txt file:

list(APPEND CMAKE_REQUIRED_LIBRARIES "-Wl,--default-symver")
   check_c_source_compiles(
   "
   int main (void)
   {
      return 0;
   }
   "
   DSYMVER_WORKS
   )
   list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "-Wl,--default-symver")

   if (SYMVER_WORKS)
      set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--default-symver")
   else()

It checks for SYMVER_WORKS, while the variable being changed by the compilation test is DSYMVER_WORKS. When fixing this, the exported symbols were libjansson.so.4, as expected.
So I think this is an additional problem/cause for the cmake symbols not being consistent.