title: Cross-compiling GSL 1.16 for ARM
body: <p>I am trying to cross-compile the GNU Scientific Library (gsl, v1.16) for ARM architecture (specifically the Raspberry Pi). I have used the following to configure;</p>
  
  <pre><code>CROSS=armv6j-hardfloat-linux-gnueabi
  ./configure --host=x86_64-pc-linux-gnu --build=$CROSS --target=$CROSS \
  CC=/usr/bin/$CROSS-gcc \
  CXX=/usr/bin/$CROSS-g++ \
  AR=/usr/bin/$CROSS-ar \
  RANLIB=/usr/bin/$CROSS-ranlib \
  CFLAGS="-march=armv6 -mfloat-abi=hard -mfpu-vfp"
  </code></pre>
  
  <p>I get the following error messages:</p>
  
  <pre><code>libtool: compile:  /usr/bin/armv6j-hardfloat-linux-gnueabi-gcc 
  -DHAVE_CONFIG_H -I. -I.. -I.. -march=armv6 -mfloat-abi=hard -mfpu=vfp 
  -MT read.lo -MD -MP -MF .deps/read.Tpo -c read.c -o read.o
  In file included from fp.c:10:0:
  fp-gnux86.c: In function 'gsl_ieee_set_mode':
  fp-gnux86.c:42:15: error: '_FPU_SINGLE' undeclared (first use in this function)
  fp-gnux86.c:42:15: note: each undeclared identifier is reported only once for each function it appears in
  fp-gnux86.c:45:15: error: '_FPU_DOUBLE' undeclared (first use in this function)
  fp-gnux86.c:48:15: error: '_FPU_EXTENDED' undeclared (first use in this function)
  fp-gnux86.c:57:15: error: '_FPU_RC_NEAREST' undeclared (first use in this function)
  fp-gnux86.c:60:15: error: '_FPU_RC_DOWN' undeclared (first use in this function)
  fp-gnux86.c:63:15: error: '_FPU_RC_UP' undeclared (first use in this function)
  fp-gnux86.c:66:15: error: '_FPU_RC_ZERO' undeclared (first use in this function)
  fp-gnux86.c:76:13: error: '_FPU_MASK_DM' undeclared (first use in this function)
  make[2]: *** [fp.lo] Error 1
  </code></pre>
  
  <p>I am compiling on a 64 bit Linux Gentoo system. I have used the Gentoo toolchain to set-up my cross-compiler. Any pointers to what I am doing wrong are highly appreciated.</p>
  
  <p>Thanks in advance!</p>