Welcome to Android Gaming - Pro Android Games - page 17

CROSS=arm-none-linux-gnueabi-
GCC=${CROSS}ld

# Uncomment for debugging
#echo "${GCC} $LD_FLAGS $LIB_PATHS $@ $LIBRARIES"

# Go!
${GCC} $LD_FLAGS $LIB_PATHS $@ $LIBRARIES

The ald script defines variables similar to those use used by the agcc script, which specify the
location of the required software components, plus some extra linker variables:

LIBRARIES : This variable defines the basic libraries against which the final binary
should be linked. These are the C runtime ( -lc ), the Math library ( -lm ), and
libgcc.a , which contains extra symbols required at link time. Note that the linker
will expand -lc to the name libc.so when reading the library from the file system.

•

LIB_PATHS : Besides the library names defined in the previous step, the linker needs
to be able to find the libraries on the file system. Thus, you need to tell it where to
look. The -Lpath1 , - Lpath2 , and so on tell the compiler where to look for libraries.
Also, -rpath sets the runtime shared library search path. You need to define two
runtime search paths:

•

-rpath /system/lib is the location of the runtime libraries in the device. It
must be defined so the program will be able to run properly in the device
itself.

•

-rpath ${SYS_ROOT}/lib is the location of the same libraries on the desktop
system. It is required so the binary can compile properly.

•

•

LD_FLAGS : This variable defines linker flags. Two flags are used by the script:

--dynamic-linker=/system/bin/linker sets a program to use as the dynamic
linker. In this case, /system/bin/linker is the device.

•

• -nostdlib tells the linker not to use the standard libraries (C runtime, Math
library, and so on) defined by the toolchain, but instead use the libraries
defined by the user at link time.
And, finally, the command ${GCC} $LD_FLAGS $LIB_PATHS $@ $LIBRARIES will expand to the
following:
$ arm-none-linux-gnueabi-ld --dynamic-linker=/system/bin/linker
-nostdlib -rpath /system/lib
-rpath /user/home/tmp/android/system/lib
-L/user/home/tmp/android/system /lib
-L/usr/lib/jvm/java-6-sun/jre/lib/i386
-L. [USER_ARGUMENTS] -lc -lm
/user/home/Desktop/android/arm-2008q3/lib/gcc/
arm-none-linux-gnueabi/4.3.2${LIBDIR}/libgcc.a

Note that $@ in the script will expand to all arguments sent by the user in the command line.