/usr/lib/gcc/x86_64-linux-gnu/4.6/include/ is in gcc-4.6 4.6.3-1ubuntu5.
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/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/README
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/limits.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/linux/
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/linux/a.out.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/syslimits.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/abmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/ammintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/avxintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/bmiintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/bmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/cpuid.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/cross-stdarg.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/emmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/float.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/fma4intrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/ia32intrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/immintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/iso646.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/lwpintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/mm3dnow.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/mm_malloc.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/mmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/nmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/omp.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/pmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/popcntintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/quadmath.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/quadmath_weak.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/smmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdarg.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdbool.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stddef.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdfix.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdint-gcc.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdint.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/tbmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/tmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/unwind.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/varargs.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/wmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/x86intrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/xmmintrin.h
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/xopintrin.h