Recompile with -Xlint in Android studio

Staying out of deprecated methods is useful, so your app won’t run in some compatibility mode on the device. Plus having clean build output is also nice 🙂

While building an app, Gradle may produces some warnings telling you that some input files are using unchecked or unsafe operations or they are overriding a deprecated API.

Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

As the message suggest, we should recompile with -Xlint to get more details about the warnings.

In the app level build.gradle file

app level build.gradle file

we should add a section labelled  allprojects{}(if not already present).

In the allprojects{} section we will instruct Gradle to apply custom compiler arguments for each task involving  Java code compilation.

allprojects {
    tasks.withType(JavaCompile) {
        options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
    }
}

Now each time we build our app we will get detailed output of the unchecked or unsafe operations and the deprecated API we are using.

Tip: if for some reason we want to continue using a deprecated API and just suppress the warnings, we could annotate the deprecated method with the

@SuppressWarnings("deprecation")

annotation.

ERROR: dev-python/cryptography-1.1.2::gentoo failed (compile phase)

Latest

emerge --sync
emerge --update --deep --newuse @world

broke “dev-python/cryptography” on my development “server”. By server I mean Intel Celeron at 400Mhz with 768Mb of RAM. Currently running MySQL, Apache, Apache Tomcat, Samba and Deluge.

i686-pc-linux-gnu-gcc -O2 -march=pentium2 -pipe -fomit-frame-pointer -fno-ident -fPIC -I/usr/include/python2.7 -c /var/tmp/portage/dev-python/cryptography-1.1.2/work/cryptography-1.1.2-python2_7/temp.linux-i686-2.7/_openssl.c -o /var/tmp/portage/dev-python/cryptography-1.1.2/work/cryptography-1.1.2-python2_7/temp.linux-i686-2.7/var/tmp/portage/dev-python/cryptography-1.1.2/work/cryptography-1.1.2-python2_7/temp.linux-i686-2.7/_openssl.o
/var/tmp/portage/dev-python/cryptography-1.1.2/work/cryptography-1.1.2-python2_7/temp.linux-i686-2.7/_openssl.c:2096:15: error: ‘SSLv2_method’ redeclared as different kind of symbol
 SSL_METHOD* (*SSLv2_method)(void) = NULL;

As the build error says dev-python/cryptography is looking for SSLv2. Doing

equery u openssl
[ Legend : U - final flag setting for installation]
[        : I - package is installed with flag     ]
[ Colors : set, unset                             ]
 * Found these USE flags for dev-libs/openssl-1.0.2h-r2:
 U I
 + + asm                : Support assembly hand optimized crypto functions (i.e. faster run time)
 + + bindist            : Disable EC algorithms (as they seem to be patented) -- note: changes the ABI
 - - cpu_flags_x86_sse2 : Use the SSE2 instruction set
 - - gmp                : Add support for dev-libs/gmp (GNU MP library)
 - - kerberos           : Add kerberos support
 - - rfc3779            : Enable support for RFC 3779 (X.509 Extensions for IP Addresses and AS Identifiers)
 - - sctp               : Support for Stream Control Transmission Protocol
 - - sslv2              : Support for the old/insecure SSLv2 protocol -- note: not required for TLS/https
 + + sslv3              : Support for the old/insecure SSLv3 protocol -- note: not required for TLS/https
 - - static-libs        : Build static versions of dynamic libraries as well
 - - test               : Workaround to pull in packages needed to run with FEATURES=test. Portage-2.1.2 handles this internally, so don't set it in
                          make.conf/package.use anymore
 + + tls-heartbeat      : Enable the Heartbeat Extension in TLS and DTLS
 - - vanilla            : Do not add extra patches which change default behaviour; DO NOT USE THIS ON A GLOBAL SCALE as the severity of the meaning changes
                          drastically
 + + zlib               : Add support for zlib (de)compression

Reveled that OpenSSL is build with ought SSLv2 suport. Adding sslv2 use flag for OpenSSL and rebuilding resolved the problem.

echo "dev-libs/openssl sslv2" > /etc/portage/package.use/openssl

According to me, this is a bug in “dev-python/cryptography“. The ebuild should do some kind of checking if sslv2 use flag is enabled, or it should introduce use flags controlling the version of ssl used.