two-step: Links against libintl.so if LNS

The plugin two-step cannot be loaded on a system based on the musl libc library.

01:25:00.427 ply-utils.c:536:ply_open_module                               : Could not load module "/usr/lib/plymouth/two-step.so": Error relocating /usr/lib/plymouth/two-step.so: libintl_dgettext: symbol not found

The utilities ldd and objdump reports the missing symbol:

# ldd /usr/lib/plymouth/two-step.so
/lib/ld-musl-aarch64.so.1 (0x7fad6c0000)
libply-splash-graphics.so.5 => /usr/lib/libply-splash-graphics.so.5 (0x7fad683000)
libply-splash-core.so.5 => /lib/libply-splash-core.so.5 (0x7fad654000)
libply.so.5 => /lib/libply.so.5 (0x7fad629000)
libc.musl-aarch64.so.1 => /lib/ld-musl-aarch64.so.1 (0x7fad6c0000)
libpng16.so.16 => /usr/lib/libpng16.so.16 (0x7fad5ea000)
libudev.so.1 => /lib/libudev.so.1 (0x7fad5b7000)
libz.so.1 => /lib/libz.so.1 (0x7fad590000)
Error relocating /usr/lib/plymouth/two-step.so: libintl_dgettext: symbol not found

# objdump -T /usr/lib/plymouth/two-step.so | grep gettext
0000000000000000      D  *UND*	0000000000000000 libintl_dgettext

The missing symbol is archived to the library libintl.so (running plymouthd with the environment LD_PRELOAD=/usr/lib/libintl.so fixes the issue).

# objdump -T /usr/lib/libintl.so | grep gettext
0000000000005aa0 g    DF .text	0000000000000008 libintl_dngettext
0000000000007134 g    DF .text	0000000000000004 dgettext
0000000000002300 g    DF .text	0000000000000014 libintl_dcgettext
0000000000005aa8 g    DF .text	0000000000000018 libintl_ngettext
0000000000007130 g    DF .text	0000000000000004 gettext
0000000000007140 g    DF .text	0000000000000004 dngettext
0000000000002314 g    DF .text	0000000000000008 libintl_dgettext
000000000000231c g    DF .text	0000000000000010 libintl_gettext
0000000000007138 g    DF .text	0000000000000004 dcgettext
000000000000713c g    DF .text	0000000000000004 ngettext
0000000000005a90 g    DF .text	0000000000000010 libintl_dcngettext
0000000000007144 g    DF .text	0000000000000004 dcngettext

The story is much complicated, however, the autotools does the magic.

The GNU gettext FAQ1 says explicitly that if the program's final link command does not contain the option -lintl...

In this case it's likely a bug in the package you are building: The package's Makefiles should make sure that “-lintl” is used where needed.

Autoconf sets both variables LIBINTL and LTLIBINTL with the appropriate link options if NLS is being used. These variables are left empty if the option --disable-nls is set at the configure step.

LIBINTL = /usr/lib/libintl.so
LTLIBINTL = -L/usr/lib -lintl

This links the plugin two-step to libintl by adding the libtool variable LTLIBINTL to the list of the plugin's libraries to link with.

Note: The plugin two-step loads fine on a system based on the glibc library (without this commit). The plugin uses the intermediate symbol dcgettext which is implemented by the glibc instead of the remapped symbol libintl_gettext which is implemented by gettext in libintl.

On glibc:

# objdump -T /usr/lib/plymouth/two-step.so | grep gettext
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 dcgettext

$ objdump -T /usr/lib/libc.so.6 | grep gettext
0000000000037ec0  w   DF .text	0000000000000014  GLIBC_2.2.5 dcngettext
0000000000036630  w   DF .text	0000000000000013  GLIBC_2.2.5 dcgettext
0000000000037ef0  w   DF .text	000000000000001a  GLIBC_2.2.5 ngettext
0000000000036660  w   DF .text	0000000000000013  GLIBC_2.2.5 gettext
0000000000036630 g    DF .text	0000000000000013  GLIBC_2.2.5 __dcgettext
0000000000036650  w   DF .text	000000000000000e  GLIBC_2.2.5 dgettext
0000000000036650 g    DF .text	000000000000000e  GLIBC_2.2.5 __dgettext
0000000000037ee0  w   DF .text	000000000000000f  GLIBC_2.2.5 dngettext

On musl:

# objdump -T /usr/lib/plymouth/two-step.so | grep gettext
0000000000000000      D  *UND*	0000000000000000 libintl_dgettext

# objdump -T /lib/libc.musl-aarch64.so.1 | grep gettext
0000000000025724 g    DF .text	0000000000000010 dcgettext
0000000000027828 g    DF .text	0000000000000014 ngettext
0000000000025734 g    DF .text	0000000000000008 dngettext
000000000002573c g    DF .text	0000000000000010 dgettext
000000000002781c g    DF .text	000000000000000c gettext
0000000000025294 g    DF .text	0000000000000490 dcngettext

# objdump -T /usr/lib/libintl.so | grep libintl_dgettext
0000000000002314 g    DF .text	0000000000000008 libintl_dgettext

However, this commit changes nothing for system based on glibc as the magic of the Autoconf leaves the LIBINTL and LTLIBINTL empty even if the NLS is being used.

Signed-off-by: Gaël PORTAY gael.portay@collabora.com