Comment 1 for bug 1056340

"-m64" didn't help, either.

Protocol of "gcc -v":

cc -v -L/usr/lib/x86_64-linux-gnu -L/lib/x86_64-linux-gnu -lm sieve1-4.o sieveMethods.o -o sieve1-4
Using built-in specs.
COLLECT_GCC=cc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6/:/usr/lib/gcc/x86_64-linux-gnu/4.6/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6/:/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-L/usr/lib/x86_64-linux-gnu' '-L/lib/x86_64-linux-gnu' '-o' 'sieve1-4' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.6/collect2 --sysroot=/ --build-id --no-add-needed --as-needed --eh-frame-hdr -m elf_x86_64 --hash-style=gnu -dynamic-linker /lib64/ld-linux-x86-64.so.2 -z relro -o sieve1-4 /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o -L/usr/lib/x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.6 -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../.. -lm sieve1-4.o sieveMethods.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crtn.o
sieve1-4.o: In function `main':
sieve1-4.c:(.text.startup+0x8c): undefined reference to `trunc'
sieve1-4.c:(.text.startup+0x2c4): undefined reference to `sqrt'
collect2: ld returned 1 exit status
make: *** [sieve1-4] Error 1