Without the change build fails on upstream gcc-10 as:
ld: tool.o:(.bss+0x0): multiple definition of `view'; color.o:(.bss+0x0): first defined here
ld: tool.o:(.bss+0x820): multiple definition of `video'; color.o:(.bss+0x820): first defined here
ld: png_save.o:(.bss+0x0): multiple definition of `view'; color.o:(.bss+0x0): first defined here