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
The change leaves variable definitions only in C files.
gcc-10 changed the default from -fcommon to fno-common: https://gcc.gnu.org/PR85678
As a result build fails as:
The change leaves variable definitions only in C files.