configure.ac: Add code to detect bionic C library

This adds a new IS_BIONIC define that can be used to detect whether we are
building with eglibc or with bionic.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
configure.ac: Cleanup, comments, indent, ...

This commit doesn't do any functional change to configure.ac but does a fair
amount of cleaning up.

It re-orders the various blocks by type (options, checks, expands, ...).
It also consistently uses tabs for indents.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Replace all reference to ushort by unsigned short

ushort appears to be a glibc specific type which doesn't exist in
bionic, this commit simply replace all occurences by the equivalent
unsigned short type.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Support both getline and fgetln

Some libc implementations don't have the getline function but instead
have an equivalent fgetln function.

Add code to detect both and use whatever is available.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
No need to link against rt and util on bionic

When building on bionic, -lrt and -lutil only cause a build failure.
Dropping those fixes the build, so it appears that the symbols are defined
in the main library.

This commit moves -lrt and -lutil under a !IS_BIONIC check.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Replace get_current_dir_name by getcwd

get_current_dir_name appears to be specific to glibc. Replace that call
by an equivalent getcwd call.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Add/remove extra includes

While cross-building with bionic, a number of failures were triggered by some
missing includes and in a few cases by extra unused includes.

This commit updates the various headers based on those observations.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
conf.c: Define LO_FLAGS_AUTOCLEAR if it's not

LO_FLAGS_AUTOCLEAR isn't defined on bionic, so add an extra ifndef
and set it to its usual value if it's not.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
clone: Support bionic's clone() defintion

The clone() call in bionic is very slightly different.
This updates namespace.h to support both glibc and bionic.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
tty.h: Ship our own minimal openpty.h

bionic is missing an openpty() function, so ship our own and only
build it and use it on bionic.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Don't hard depend on capability.h and libcap

In the effort to make LXC work with non-standard Linux distros, this change
allows for the user to build LXC without capability support.

This effectively will cause LXC not to link against libcap and will turn all
the _cap_ functions into no-ops.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
personality.h: Make the personality code optional

Some platforms don't have personality.h in their C library, this change
adds buildtime detection for the header and turns off the personality setting
code in those cases.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Workaround missing functions in other libc

Some libc implementation (bionic) is lacking some of the syscall functions
that are present in the glibc.

For those, detect at build time the they are missing and implement a minimal
syscall() wrapper that will essentially give the same result as the glibc
function.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Make utmpx.h optional

This adds code detecting the presence of utmpx.h and in its absence, turns the
utmp related functions into no-ops.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Add a bionic_alphasort function on bionic

alphasort doesn't have the right signature on bionic which causes the build to
fail. This implements a new bionic_alphasort function when building on bionic
providing the right signature and a functional equivalent of glibc's alphasort.

This signature problem with alphasort was fixed in upstream bionic but hasn't
been released yet. This commit can therefore be reverted as soon as the
following commit hits the Android NDK: 40e467ec668b59be25491bd44bf348a884d6a68d

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Replace strdupa call by standard strdup

strdupa appears to only exist in the standard glibc but at least not in bionic.
Replace the two strdupa calls we have by a standard strdup.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
caps.h: Rename __errno to ___errno

At least bionic defines __errno, so this was causing a conflict in caps.h
leading to build failure. Renaming to ___errno avoids that duplicate
definition.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Add local implementation of mntent.h

Bionic (at least) is missing some of the usual mntent functions.
This adds code defining those that we need when they're missing from the C
library.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
conf.c: Cleanup __S_ISTYPE

__S_ISTYPE doesn't exist in all C libraries, so define it if it's missing.
Additionaly, replace one occurence where it wasn't actually needed.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
lxc_unshare: Replace getpw*_r by getpw*

Bionic and maybe some other libc implementations lack the _r nss functions.
This replaces our current getpwnam_r and getpwuid_r calls by getpwnam and
getpwuid.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>