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goelfmemory-alignment

ELF go binaries default byte alignment

I empirically see that go ELF binaries use 16 bytes alignment. For example:

$ wget https://github.com/gardener/gardenctl/releases/download/v0.24.2/gardenctl-linux-amd64
$ readelf -W -s gardenctl-linux-amd64 | grep -E "FUNC" | wc -l
44746
$ readelf -W -s gardenctl-linux-amd64 | grep -E "0[ ]+[0-9]* FUNC" | wc -l
44744

so vast majority have 0 in their least significant byte. Is it always like that in go binaries?

Solution

  • This depends on the platform. If you have a source repo checked out:

    % cd go/src/cmd/link/internal
% grep "funcAlign =" */*.go
amd64/l.go:     funcAlign = 32
arm/l.go:       funcAlign = 4 // single-instruction alignment
arm64/l.go:     funcAlign = 16
mips64/l.go:    funcAlign = 8
ppc64/l.go:     funcAlign = 16
riscv64/l.go:   funcAlign = 8
s390x/l.go:     funcAlign = 16
x86/l.go:       funcAlign = 16

    the alignment for amd64 may go back down to 16 in the future; it is 32 for a while because of https://github.com/golang/go/issues/35881