Default function arguments in C are specified like this: int func(int a = 10) {} // just a dummy function
Now I save that in a file called foo.c The above piece of code is valid in C as well as C++ Now see this: nilesh@Linux ~ $ cat /tmp/foo.c int func(int a = 1) {} nilesh@Linux ~ $ gcc /tmp/foo.c /tmp/foo.c:1:16: error: expected ‘;’, ‘,’ or ‘)’ before ‘=’ token nilesh@Linux ~ $ g++ /tmp/foo.c /usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/../../../../lib64/crt1.o: In function `_start': (.text+0x20): undefined reference to `main' collect2: ld returned 1 exit status nilesh@Linux ~ $ gcc -v Using built-in specs. COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.3/gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.3/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /media/500GB/gentoo_portage/tmp/portage/sys-devel/gcc-4.5.3-r1/work/gcc-4.5.3/configure --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.3 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/include/g++-v4 --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec --disable-fixed-point --without-ppl --without-cloog --disable-lto --enable-nls --without-included-gettext --with-system-zlib --disable-werror --enable-secureplt --enable-multilib --enable-libmudflap --disable-libssp --enable-libgomp --enable-cld --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/python --enable-checking=release --disable-libgcj --enable-languages=c,c++,fortran --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.5.3-r1 p1.0, pie-0.4.5' Thread model: posix gcc version 4.5.3 (Gentoo 4.5.3-r1 p1.0, pie-0.4.5) nilesh@Linux ~ $ g++ -v Using built-in specs. COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.3/g++ COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.3/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /media/500GB/gentoo_portage/tmp/portage/sys-devel/gcc-4.5.3-r1/work/gcc-4.5.3/configure --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.3 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/include/g++-v4 --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec --disable-fixed-point --without-ppl --without-cloog --disable-lto --enable-nls --without-included-gettext --with-system-zlib --disable-werror --enable-secureplt --enable-multilib --enable-libmudflap --disable-libssp --enable-libgomp --enable-cld --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.5.3/python --enable-checking=release --disable-libgcj --enable-languages=c,c++,fortran --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.5.3-r1 p1.0, pie-0.4.5' Thread model: posix gcc version 4.5.3 (Gentoo 4.5.3-r1 p1.0, pie-0.4.5) Why is this happening? O_o -- Nilesh Govindarajan http://nileshgr.com