/tmp/ccBQzrvx.o: In function `Output()':
foo.cc:(.text+0x81): relocation truncated to fit: R_X86_64_PC32 against symbol `a' defined in .bss section in /tmp/ccBQzrvx.o
/tmp/ccBQzrvx.o: In function `change()':
foo.cc:(.text+0x10c): relocation truncated to fit: R_X86_64_PC32 against symbol `a' defined in .bss section in /tmp/ccBQzrvx.o
/tmp/ccBQzrvx.o: In function `_GLOBAL__sub_I_a':
foo.cc:(.text.startup+0x33): relocation truncated to fit: R_X86_64_PC32 against `.bss'
foo.cc:(.text.startup+0x51): relocation truncated to fit: R_X86_64_PC32 against `.bss'
collect2: error: ld returned 1 exit status