libdwarf: Support consumption of compressed ELF sections

[markj]

Summary

This lets ctfcovert work on userland code after commit c910570e7573
("Use compressed debug in standalone userland debug files by default").

Reported by: avg
MFC after: 1 week
Sponsored by: The FreeBSD Foundation

[avg]

contrib/elftoolchain/libdwarf/libdwarf_elf_init.c

232

Got a compilation error here on amd64 when building lib32. &size has an incompatible pointer type.
Changing csize type to unsigned long fixed the build.

[avg]

Other than the lib32 error, everything seems to have worked fine.

contrib/elftoolchain/libdwarf/libdwarf_elf_init.c

232

Full error, just in case:

/usr/devel/git/trant/contrib/elftoolchain/libdwarf/libdwarf_elf_init.c:232:31: error: incompatible pointer types passing 'size_t *' (aka 'unsigned int *') to parameter of type 'uLongf *' (aka 'unsigned long *') [-Werror,-Wincompatible-pointer-types]
        if (uncompress(ed->ed_alloc, &csize, (char *)ed->ed_data->d_buf + hsize,
                                     ^~~~~~
/usr/obj/trant/usr/devel/git/trant/amd64.amd64/obj-lib32/tmp/usr/include/zlib.h:1266:59: note: passing argument to parameter 'destLen' here
ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
                                                          ^
1 error generated.

[markj]

size_t -> unsigned long

[markj]

Gentle ping, in case anyone else is planning on reviewing this.

[emaste]

Do other libelf/libdwarf implementations provide the same functionality?

[markj]

In D33139#752666, @emaste wrote:

Do other libelf/libdwarf implementations provide the same functionality?

Not sure about libelf, but the SGI-derived libdwarf supports compressed sections, yes.